Dissertations / Theses: 'Mediterranean streams'

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Romaní, i. Cornet Anna M. "Heterotrophic and autotrophic metabolism in Mediterranean streams." Doctoral thesis, Universitat de Barcelona, 1997. http://hdl.handle.net/10803/1447.

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Helerotrophic (cetoenzymatic and respiratory activities) and autotrophic (photosynthetic activity) metabolism on epilithic strearn biofilms have been measured, analyzed and studied in this thesis. The main objective was to determine the role of the heterotrophs in organic matter use (autochthonous and allochthonous) in Mediterranean streams. In Riera Major, a siliceous forest Mediterranean stream, the capacity to cleave polysaccharides is more important in the epipsammon than in the epilithon. The heterotrophic activity in the surface sediment was higher than in the subsurface sediment. This has been related to the higher quantity and quality of the organic matter which accumulates in the surface sediment. A drastic increase in benthic algal biomass and ectoenzymatic activities was observed in a stream stretch where the riparian vegetation had been removed. The bedrock of La Solana, a calcareous Mediterranean stream, is covered by a thick cyanobacterial crust with a layered structure similar to a stromatolite where different algal patches developed. This structure has a great capacity for organic matter utilization and seems to be adapted to the drastic environmental changes characteristic of Mediterranean streams. Specially, the ectoenzymatic activities were immediately recovered after a dry period. The ectoenzyme kinetics in Riera Major and La Solana was investigated along a seasonal study. In La Solana Vmax values for the three enzymes studied were always higher and the turnover time of substrate hydrolysis was lower (faster) than in the Riera Major which might be related to the more labile substrates for the heterotrophs (organic compounds from the primary producers) while Riera Major is receiving a more recalcitrant material (Ieaf from the riparian vegetation). The ectoenzymatic activity in the epilithic biofiIm of a fourth-order river, the Ter, followed a markedly seasonal pattern, most activities and biomass showing a peak in spring and autumn. Discharge and nutrients were the most important factors for Ihe regulation of biofilm metabolism. The epilithic ectoenzymatic activities were also measured in a Central European mountain stream. Colonization studies (by using clay tiles as substrates for the epilithon) showed that algal material is used by the heterotrophs as an organic matter source. METODOLOGIA: La tècnica principal utilitzada en aquest estudi és la mesura de les activitats ectoenzimàtiques en els diferents biofilms -epilítics. Epipsàmmícs, crosta cianobacteriana- de nus. En aquest capítol es descriu el desenvolupament d'aquesta metodologia (procés d'incubació, concentració dels substrats, temps d'incubació) i la seva alplicació en l'estudi dels biofilms. Així mateix són descrites les altres mesures metabóliques aplicades en aquest estudi (activitat respirotória, ETS, i activitat fotosintètica, incorporació de H(14)CO3) així com la densitat i biomassa algals (comptatge de cèl.lules, clorofil.la-a) i bacterianes (microscopia de fluorescència) i la mesura dels paràmetres físics i quimícs del riu.

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Merciai, Roberto. "Effects of global change on fish assemblages in Mediterranean streams." Doctoral thesis, Universitat de Girona, 2016. http://hdl.handle.net/10803/405192.

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L'objectiu d'aquesta tesi és de'explorar alguns aspectes de l'impacte humà sobre les poblacions de peixos i altres components dels ecosistemes fluvials Mediterranis de Catalunya. Es va mostrar com els peixos del Riu Llobregat acumulen quantitats significatives de metalls pesants, amb concentracions en el múscul que varien al llarg del riu i segons l'espècie i la talla dels peixos. En el Riu Tordera, afectat per l'extracció d'aigua, el règim de temperatures es veu alterat en correspondència dels trams intermitents, en els quals la probabilitat de supervivència i l'abundancia dels peixos , i en menor mesura el creixement i la condició corpòria, també pateixen les conseqüencies de l'alteració hidrològica The goal of this thesis is to explore some aspects of anthropogenic impact on the fish populations and other components of two Mediterranean stream ecosystems in Catalonia NE Spain). It was shown how Llobregat River's fish accumulate significant trace metal quantities, with muscle concentrations varying across sampling sites along the river, fish species and size. In the Tordera Stream, affected by water abstraction, the temperature regime was disrupted in correspondence of the intermittent reaches, where fish abundance and survival probability and, at a lower extent, growth and body condition, also suffered the consequences of hydrologic alteration

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Canals, Merseburger Mª Goretti. "Nutrient dynamics and metabolism in Mediterranean streams affected by nutrient inputs from human activities." Doctoral thesis, Universitat de Barcelona, 2006. http://hdl.handle.net/10803/1434.

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A full understanding of nutrient cycling in lotic ecosystems is crucial given the increasing influence of human activities on the eutrophication of streams and rivers. However, existing knowledge about nutrient cycling in human-altered streams (i.e., receiving point and diffuse sources) is still limited. The general objective of this dissertation was to examine point source effects on stream functional attributes, such as nutrient retention, denitrification and metabolism rates. We also quantified how the studied biogeochemical processes contribute to remove dissolved inorganic nitrogen (DIN) from point and diffuse sources, and examined relationships between N uptake measured based on experimental nutrient additions and N demand estimated from metabolism measurements. We selected two reaches located upstream and downstream of a point source in two streams draining a forest- and an agriculturaldominated catchments. Hence, the point source represented the main human influence in the forested stream, whereas the agricultural stream also received diffuse sources. The point source increased concentrations of ammonium (NH4 +-N), nitrate (NO3--N), soluble reactive phosphorus (SRP) and dissolved organic carbon in the forested stream, while only increased SRP concentration in the agricultural stream. The point source effect on water chemistry was likely to be overwhelmed by diffuse sources in this latter stream. Accordingly, point source inputs decreased nutrient retention efficiency, and increased denitrification and metabolism rates in the forested stream, whereas these effects were less clear in the agricultural stream. Retention of NH4 +-N was similar to potential nitrification rates in the two reaches of the two study streams, suggesting the importance of this process in NH4 +-N removal from the water column. Retention of NO3--N was similar to potential denitrification rates in the forested stream, suggesting the importance of this process as a net sink of NO3 --N. In contrast, high NO3--N fluxes in the agricultural stream resulted in low efficiency of denitrifiers to remove N from the water column. Hence, in-stream processes controlled DIN export in the forested stream, despite point source inputs, whereas much of the NO3--N reaching the channel via diffuse sources was lost downstream in the agricultural stream. Finally, estimated N demand was not correlated with measured N demand in any of the study reaches. Nevertheless, decoupling between measured and estimated N demand was clearly lower for the upstream reach of the forested stream (i.e., site with lowest human influence) than for the downstream reach and the two reaches of the agricultural stream (i.e., sites receiving nutrient inputs from human activities). Hence, coupling between carbon metabolism and N uptake in stream ecosystems is likely to become weaker with increasing anthropogenic nutrient inputs.

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Colls, Lozano Miriam. "Biofilm responses to flow intermittency in Mediterranean rivers." Doctoral thesis, Universitat de Girona, 2020. http://hdl.handle.net/10803/670845.

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Currently, global change is promoting the spatiotemporal occurrence of temporary streams, altering fluvial ecosystem function and structure, and the ecosystem services they provide. To effectively protect fluvial ecosystems, a detailed understanding of the effects of hydrological regime changes on their biodiversity and functioning is needed. Organisms inhabiting temporary streams are directly affected by their hydrological regime, including the stream biofilm. Biofilms are associations of microorganisms and they are of particular relevance in temporary streams because of their diversity, abundance, and key role in ecosystem processes. Therefore, understanding biofilm response to hydrological regime variability is key to understand the implications of increasing non-flow periods on fluvial ecosystems. The results of this thesis demonstrate the non-flow duration as a key influence on the structure and functioning of river biofilms, the importance of maintaining photoautotrophic stream biodiversity to preserve stream ecosystems functioning and the protective role of canopy cover to protect these communities El canvi global està promovent l’aparició de rius intermitents, alterant funcionament, estructura i serveis ecosistèmics dels sistemes fluvials. Per a protegir efectivament els ecosistemes fluvials, es necessita un coneixement detallat dels efectes del canvi de règim hidrològic sobre la seva biodiversitat i funcionament. Els organismes que habiten els rius temporals estan directament afectats pels canvis hidrològics, inclòs el biofilm. Els biofilms són associacions de microorganismes i particularment rellevants als rius temporals per la seva diversitat, abundància i paper en processos ecosistèmics. Així, entendre la resposta del biofilm a la variabilitat del règim hidrològic és clau per entendre les implicacions del increment del període sec als ecosistemes fluvials. Els resultats d'aquesta tesi demostren la duració del període sec com a vector d'estructura i funcionament del biofilm, la importància de mantenir la biodiversitat fotoautòtrofa per preservar el funcionament ecosistèmic i el paper protector de la coberta vegetal sobre aquestes comunitats

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Ribot, Bermejo Miquel. "Effects of human activities on nitrogen cycling in Mediterranean streams: contrasts between nitrate and ammoniun dynamics." Doctoral thesis, Universitat de Barcelona, 2015. http://hdl.handle.net/10803/296678.

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Human activities have increased dissolved inorganic nitrogen (DIN) availability and modified the relative proportion of DIN as NO3- or NH4+ in running waters. Because nitrogen (N) is an essential element for in-stream biota, increases in DIN availability derived from human activity can alter biological N demand as well as dominant biogeochemical uptake pathways. Ultimately, this may have relevant implications for in-stream nutrient cycling and downstream transport. The general goal of the present Thesis was to understand how in-stream DIN uptake is affected by changes in DIN availability and speciation induced by human activities. We hypothesized that DIN uptake in streams will be influenced by the relative availability of NO3- and NH4+ because biotic assimilatory uptake demand and dissimilatory uptake processes differ between the two DIN species. Results from this Thesis indicated that microbial communities developing on inorganic streambed substrata (biofilms) mostly rely on NO3- as an N source, likely due to the general higher ambient availability of NO3-. However, while NH4+ concentration only accounted for 6% of total DIN (sum of NO3- and NH4+), biofilm assimilation of NH4+ accounted for 27% of total DIN uptake (sum of NO3- and NH4+ assimilatory uptake), suggesting preference for NH4+ with respect to NO3-. Biofilm assimilatory N uptake response to acute (i.e., hours) and chronic (i.e., weeks) enrichments in either NO3- or NH4+ were different. Acute NO3- enrichments did not enhance or even decreased biofilm assimilatory uptake of this DIN species, whereas biofilms responded in conformity to Michaelis-Menten kinetics to acute increases in NH4+ concentration. These results suggest that biofilm N uptake was already at saturation under ambient NO3- concentration, whereas it was below saturation in relation to ambient NH4+ concentration. In contrast to acute enrichments, chronic enrichments of both DIN species had a general inhibitory effect on biofilm N assimilatory uptake, being more relevant for assimilatory uptake of NO3- in those treatments enriched in NH4+. The most plausible explanation for this result was that chronic NH4+ enrichments favour the development of nitrifiers which have a high demand of NH4+ to support their growth. Besides biofilms developing on inorganic substrata, other in-stream uptake compartments (PUCs) may also contribute to assimilate in-stream DIN. In general PUCs had higher uptake rates for NH4+ than for NO3-, and biofilms developing on detritic compartments such as fine benthic organic matter (FBOM), leaves and wood accounted for the largest part of total assimilatory uptake at whole-reach scale. Dissimilatory uptake pathways associated with NO3- (i.e., denitrification and DNRA) have a low incidence on total whole-reach NO3- uptake, whereas those associated to NH4+ (i.e., nitrification) account for a remarkable fraction of total NH4+ uptake. Moreover, the study streams were clearly more efficient taking up NH4+ than NO3- regardless of the ambient DIN concentrations. However, likely due to the higher NO3- availability, uptake fluxes of this DIN species tended to be higher than those of NH4+. This pattern was further supported by results from an extensive literature survey across streams worldwide. Overall, results from this Thesis show that increases in each of the two DIN species will result in distinct responses of in-stream N uptake capacity and related biogeochemical pathways. In general, streams are more reactive for NH4+ whereas NO3- reaching the streams tends to be transported downstream without much processing. La actividad humana ha aumentado las concentraciones de nitrógeno inorgánico disuelto (NID) en los ríos. Además, la proporción relativa de las dos formas principales de NID (nitrato y amonio) depende del tipo de actividad humana en la cuenca (urbana, agrícola, industrial). El objetivo de esta Tesis ha sido el estudio de los efectos del incremento de NID sobre la captación de nitrato y amonio en ríos. Los resultados indicaron que las comunidades microbianas (biofilms) que se desarrollan en los sustratos inorgánicos del lecho de los ríos mostraron preferencia por el amonio pero asimilaron principalmente nitrato debido a la mayor disponibilidad de este. Los biofilms respondieron de forma positiva a incrementos puntuales de amonio, mientras que la respuesta frente a incrementos de nitrato fue nula o negativa. Incrementos sostenidos de la concentración de nitrato y amonio provocaron una inhibición de las tasas de asimilación de N de los biofilms. La inhibición más relevante se observó en las tasas de asimilación de nitrato en aquellos tratamientos enriquecidos con amonio, probablemente debido a la proliferación de microorganismos nitrificantes que se caracterizan por tener una alta demanda de amonio. En los experimentos a escala de tramo, los biofilms que crecen sobre sustratos orgánicos del lecho de los ríos presentaron las mayores tasas de asimilación de NID siendo más altas para el amonio que para el nitrato. Una parte importante de la captación de NID en los ríos se produjo a través de procesos no asimilatorios tales como la desnitrificación y la nitrificación. La recopilación de estudios mostró que las tasas de captación son muy variables entre ríos y que las concentraciones de las dos formas de NID podrían controlar estas tasas. En general, se observó que los ríos presentan mayor demanda de amonio, no obstante, las tasas de captación fueron parecidas para las dos formas de NID. Los resultados de esta Tesis muestran que los ríos tienen una capacidad importante de procesar los aportes de amonio procedentes de su cuenca mientras que en el caso del nitrato esta capacidad se ve reducida y tiende a ser exportado aguas abajo.

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Díez, del Molino David. "Genetic diversity and population structure of the non-native Eastern mosquitofish (Gambusia holbrooki) in Mediterranean streams." Doctoral thesis, Universitat de Girona, 2015. http://hdl.handle.net/10803/300440.

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Mosquitofish is a small, voracious, highly fecund freshwater fish species originated from northeaster America, that was introduced worldwide to control mosquito populations. In this thesis we have studied the genetics of the invasion of Mediterranean streams by the mosquitofish (Gambusia holbrooki) to discover some of the aspects that drive their successfully invasive life history. Comparison of introduced populations with the American sources of invasion indicated that there was no loss of genetic diversity due to the invasion process. Local genetic diversity levels and overall population structure were maintained among generations in introduced populations. We observed adaptive response to pollutants in the Flix reservoir, Ebro River, but that human perturbations do not prevent mosquitofish dispersal along rivers. Finally, unregulated human-assisted translocations probably increase the opportunities for colonization of new environments, and therefore need to be controlled. La gambúsia és un peix molt voraç i fecund originari de les masses d’aigua dolça del nord-est d’Amèrica, que va a ser introduïda en tot el món pel control biològic de les poblacions de mosquit. En aquesta tesis se analitzen els processos genètics relacionats amb l’èxit invasor de la gambúsia (Gambusia holbrooki) en les conques mediterrànies. Les poblacions de gambusia introduïdes catalanes mantenen els nivells de diversitat genètica presents a les poblacions Americànes que van ser les fonts dels invasors de Europa. En aquestas poblacions introduïdes, els nivells locals i patrons hidrogràfics de diversitat genètica es mantenen entre generacions. Hi a una resposta selectiva als contaminants en les poblacions de gamusia a l’embassament de Flix, riu Ebro, però aquestes pertorbacions humanes no limiten la dispersió de la gambúsia. Finalment, les translocacions d’exemplars per l’home augmenten les oportunitats de colonitzar nous ambients i per això han de ser controlats.

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Mora, Gómez Juanita. "Leaf litter decomposition in Mediterranean streams: microbial processes and responses to drought under current global change scenario." Doctoral thesis, Universitat de Girona, 2014. http://hdl.handle.net/10803/285841.

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This thesis studied the principal environmental controlling factors and microbial mechanisms involved in leaf litter decomposition in Mediterranean intermittent streams. Additionally, drought disturbance in both Mediterranean intermittent and Atlantic permanent streams was also evaluated. At the Mediterranean intermittent stream leaf litter decomposition varied mainly related to seasonal variations in temperature, conductivity and current velocity. Drought clearly affected microbial assemblages and functioning in these ecosystems although this did not resulted in changes on breakdown rates. In permanent streams drought disturbance also affected microbial activity and structure, reducing breakdown velocity due to emersion of leaves. Microbial communities from nutrient enriched streams were more resistant to drought disturbance. Results suggest that under more extreme environmental variation and dry conditions expected with the global change, microbial decomposers will be severely affected. However consequences in carbon recycling will depend on to the type of drought-related disturbance, interaction with other stressors and previous communities dwelling in. En aquesta tesi s’han estudiat els factors ambientals determinants i els mecanismes microbians involucrats en la descomposició de fullaraca en rius intermitents mediterranis. També s’ha avaluat l’efecte de la sequera en rius intermitents mediterranis i permanents atlàntics. En el riu intermitent mediterrani la descomposició de fullaraca s’ha vist afectada per la variació anual de la temperatura, conductivitat i velocitat de la corrent. La sequera clarament va determinar canvis en els microorganismes descomponedors i el seu funcionament en ambdós tipus de rius, malgrat no sempre va afectar la velocitat de descomposició. Els resultats suggereixen que en condicions extremes de variació ambiental i sequera, esperats pel canvi global, els microorganismes descomponedors de la fullaraca es veuran molt afectats. No obstant, les conseqüències en el reciclatge de carboni dependran del tipus de pertorbació relacionada amb la sequera, de la interacció amb altres impactes i de les comunitats descomponedores prèvies que habiten al riu.

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Arias, del Real Rebeca. "Effects of frequency and duration of flow intermittence on biodiversity and ecosystem functioning: insights form Mediterranean streams." Doctoral thesis, Universitat de Barcelona, 2020. http://hdl.handle.net/10803/672714.

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Intermittent rivers and ephemeral streams (IRES) are watercourses that naturally and periodically cease to flow. They represent more than half of the global river network and are expanding due to global change. In this thesis, I investigate the mechanisms linking flow intermittence with biodiversity and ecosystem functioning, which sustain biogeochemical cycles and energy transfer in the system. Chapter 1 analyzes the effects of hydrology, micro-habitat (surface and subsurface zones) and biotic features on organic matter decomposition and fungal biomass, in 20 streams. In Chapter 2, I assess the effect of different flow intermittence metrics (i.e., annual intermittence regime and recent aquatic status) on aquatic biodiversity, including both taxonomic and functional-trait-based metrics, in 33 streams. Chapter 3 analyzes how aquatic hyphomycete richness and composition (beta diversity and its turnover and nestedness components) are affected by a flow intermittence gradient and how these community changes affect organic matter decomposition, in 15 streams and in a microcosm approach. Finally, in Chapter 4, I explore how changes in both leaf litter quality and quantity determine the feeding preferences and growth of an invertebrate shredder. The results of Chapter 1 show that the subsurface zone contributes to maintaining microbial decomposition during non-flow periods in IRES, mainly because of the levels of fungal biomass present in the subsurface zone. In Chapter 2, I conclude that a combination of flow intermittence metrics are needed to explain the high dynamism of the invertebrate community in IRES and potentially ecosystem functioning. Moreover, this chapter shows that hydrological variables outweigh non-hydrological factors in explaining invertebrate community variation, thereby supporting the use of the former in IRES classification and bio-monitoring routines. Chapter 3 reveals that the reduction of aquatic hyphomycete richness and species turnover as a result of flow intermittence, could have negative effects on organic matter decomposition. Finally, in Chapter 4, I provide evidence on how flow intermittence reduces the quality of leaf litter, in terms of fungal richness and composition, fungal biomass and lipid content. These changes in food quality influence the consumption rates and growth of shredders, which are able to feed selectively on higher quality leaves, even though its availability is lower. Taken together, these results will help to improve the biomonitoring and management of IRES and to a better prediction of ecosystem trajectories in response to global change.

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Puntí, Casadellà Maria del Tura. "Ecologia de les comunitats de quironòmids en rius mediterranis de referència / Ecology of Chironomidae Communities in Mediterranean Reference Streams." Doctoral thesis, Universitat de Barcelona, 2008. http://hdl.handle.net/10803/1439.

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Aquest treball aborda l'ecologia de les comunitats d'un dels grups de macroinvertebrats bentònics més diversos i abundants dels nostres rius, els quironòmids. El principal objectiu d'aquesta tesi ha estat estudiar l'estructura de les comunitats de quironòmids en rius mediterranis en condicions de referència, amb la finalitat d'augmentar el coneixement de la biodiversitat dels ecosistemes aquàtics mediterranis. Estudiar les condicions de referència es un dels prerequisits per avaluar l'estat ecològic dels rius i implementar en un futur els programes de gestió adequats seguint les directrius de la Directiva Marc de l'Aigua. Per realitzar els objectius de la tesi s'ha aplicat un protocol de mostreig estandarditzat derivat del projecte GUADALMED, en el qual juntament amb els mostrejos de les comunitats de macroinvertebrats s'han analitzat variables físiques i químiques juntament amb les característiques del bosc de ribera i de l'hàbitat aquàtic per cada punt de mostreig. Un total de 227 taxons de quironòmids han estat identificats utilitzant exclusivament larves, a diferents escales espacials (regions mediterrànies, rius i macrohàbitats) i escales temporals (primavera i estiu). A escala regional s'ha estudiat l' estructura de les comunitats de quironòmids en tres regions mediterrànies del món: la conca mediterrània, Xile i el sud-oest d'Austràlia. S'han trobat diferències de riquesa i composició taxonòmica a causa de processos històrics i de la heterogeneïtat de factors ambientals locals. A més a més en cadascuna de les regions estudiades s'han estudiat les distribucions d'abundàncies de les espècies de quironòmids presenten diferents patrons. S'han estudiat quins són els principals factors ambientals que determinen els patrons de distribució de les comunitats de quironòmids en rius mediterranis de referència a la conca mediterrània de la Península Ibèrica. La zonació longitudinal (altitud, àrea de conca, temperatura...), juntament amb la heterogeneïtat temporal són els principals gradients que afecten les variacions en l'estructura de les comunitats de quironòmids. A més a més s'ha quantificat la importància de diferents grups de variables ambientals a diferents escales: locals, regionals i geogràfiques, i es conclou que les variables locals son les que contribueixen de manera més important a la proporció de variança explicada. S'han determinat els requeriments ecològics (òptims i toleràncies de les variables ambientals d'estudi) per les espècies de quironòmids presents en aquesta zona. La variabilitat temporal (diferències primavera-estiu) és baixa en les comunitats de quironòmids de les capçaleres silíciques, mentre que en altres grups de rius com els petits rius calcaris, presenten variacions estacionals importants. Finalment, s'ha estudiat la correspondència entre les comunitats biològiques i els ecotipus fluvials establerts a la regió mediterrània ibèrica segons les directrius de la Directiva Marc de l'Aigua. S'han definit un total de cinc ecotipus fluvials utilitzant una combinació de variables hidrològiques, geològiques, morfològiques i climàtiques: (1) rius temporals, (2) trams mitjos evaporítics-calcàris, (3) capçaleres silíciques, (4) capçaleres calcàries i (5) trams mitjos-baixos. La tipologia obtinguda es va validar amb les comunitats de quironòmids (al nivell taxonòmic més baix possible d'espècie o gènere) i també amb les comunitats de macroinvertebrats (al nivell taxonòmic de família). Els nostres resultats mostren que una tipologia de rius basada amb les comunitats de macroinvertebrats i/o de quironòmids identifica diferents tipus de rius que en alguns casos coincideixen amb la tipologia ambiental però en d'altres no. Conseqüentment per establir les comunitats de referència en rius mediterranis la metodologia més correcta seria la utilització directa de les comunitats biològiques. The main objective of this thesis has been to study the structure of Chironomidae assemblages in Mediterranean reference streams. The study of freshwater biodiversity in reference conditions is a prerequisite for the implementation of effective management programs according to Water Framework Directive. To achieve that, a standardized sampling protocol for macroinvertebrate studies established in GUADALMED project has been followed. A total of 227 chironomid taxa have been identified using exclusively larvae at different spacial (Mediterranean regions, streams and macrohabitats) and temporal scales (spring and summer). At regional scale it has been studied the chironomid community structure in three Mediterranean regions around the world: South-Western Australia, Central Chile and Mediterranean Basin. Differences of taxonomical composition and richness were found among regions, mainly due to historical factors and also to local environmental constraints. Moreover, analysis of species abundances distributions showed distinctive patterns in each region. Main environmental factors that determine distribution patterns of Chironomidae communities from Spanish Mediterranean rivers have been analyzed. Variation in the assemblage structure of chironomids was primarily explained by longitudinal zonation (altitude, catchment area, temperature.) together with temporal heterogeneity (explained mainly by hydrological parameters). Moreover, in order to study ecological requirements of Chironomidae species in the study zone, optimums and tolerances to main environmental variables have been obtained for all species. Seasonal changes in the composition of Chironomidae communities have been analyzed. For instance, different biological communities from siliceous headwaters have not been detected among seasons, whereas small calcareous streams have significantly different biological communities between spring and summer. Finally, concordance among biological communities and fluvial ecotypes, established in Spanish Mediterranean region according to the guidelines of Water Framework Directive, has been analyzed. A total of five ecotypes have been defined. These ecotypes have been validated with Chironomidae assemblages (at the lowest taxonomical level) and also with macroinvertebrate assemblages (at family level). Our results show that correspondence of ecotypes with biological communities (macroinvertebrates and chironomids) mismatches in some cases. For this reason, in order to establish reference communities in Mediterranean streams, a classification based on biological data should be more appropriated than an environmental top-down classification.

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Rodríguez, Lozano Pablo. "Fire legacies in Mediterranean streams: the key roles of the riparian canopy and the top predator on food webs." Doctoral thesis, Universitat de Barcelona, 2016. http://hdl.handle.net/10803/385275.

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Wildfires are expected to increase in frequency and intensity because of climate change and changes in land use and management. In last decades, the research on fire effects on aquatic systems has grown, but it has been mainly conducted in the short- and mid-term (<5 years). Therefore, longer time frames are needed to assess fire effects on freshwater ecosystems. For instance, fire impacts on riparian and upland forests can be long-lived and wildfires often extirpate fish populations from streams, which may not recover due to barriers within the river network. Regarding fish extirpations, it is worth noting that freshwater fish are one of the most threatened fauna worldwide, especially the small-bodied species. In this context, the overarching goal of this PhD thesis was to investigate the long-term effects of a wildfire in Mediterranean streams. Specifically, this PhD thesis covered the indirect effects of two fire legacies: (1) the riparian canopy reduction and (2) the local extinction of the top predator in these streams, the endangered small-bodied fish Barbus meridionalis. The findings of this PhD thesis showed how the fire legacy in the riparian forest accelerated leaf-litter breakdown in an intermittent Mediterranean stream eight years after fire. The opening of the riparian forest canopy by fire increased light levels and water temperatures and reduced terrestrial-to-aquatic litter inputs. The increased water temperatures engendered by removal of canopy cover enhanced microbial mediated leaf breakdown. The reduction in leaf-litter inputs probably led to lower benthic organic matter levels, bringing to the observed increased shredder aggregation in leaf packs, thereby accelerating leaf breakdown rates. Our results demonstrated that the apex consumer was functionally irreplaceable, its local extinction led to the loss of an important functional role that resulted in major changes to the ecosystem's structure and function. Our mesocom experiment showed that Barbus meridionalis absence led to 'mesopredator release, and also to 'prey release despite intraguild predation, which contrasted with traditional food web theory. Top predator extirpation also changed whole macroinvertebrate community composition and increased total macroinvertebrate density. Regarding ecosystem function, periphyton primary production decreased in apex consumer absence. Moreover, we studied the feeding ecology of B. meridionalis from a functional perspective. Our results indicated that prey morphological and behavioral traits may explain prey vulnerability to predation. Specifically, the trait-based analysis showed that 10 of the 13 traits tested significantly influenced food choice (e.g. body size, concealment, locomotion, aggregation tendency, feeding habits). In addition, the leaf bags experiment confirmed that top predator absence enhanced leaf-litter breakdown, which was caused by the increase in shredder and scraper biomass in the absence of the predatory fish top-down control. Fish absence reduced leaf fungal biomass, but did not decrease microbially mediated leaf breakdown. These results suggested that leaf fungal biomass was stimulated from the bottom-up through nutrient recycling by the top predator. This PhD thesis demonstrated that past fires may have current influence on the structure and function of Mediterranean streams. Moreover, our findings evidenced that intermittent streams can be affected by the consequences of apex consumers’ extinctions, and that the loss of small-bodied top predators can lead to complex ecosystem changes. This PhD thesis interconnected several current topics in ecology research (i.e. fire effects on aquatic systems, top predator declines, and intermittent streams). Its relevance lies in the projected increase in fires in the Mediterranean region and in the current high extinction risk of small-bodied fish in freshwater ecosystems. Debido al cambio climático y a los cambios en el uso y la gestión de la tierra, se espera que la frecuencia e intensidad de los incendios forestales aumenten. La mayoría de los estudios sobre los efectos de los incendios forestales en los ecosistemas acuáticos continentales cubren el corto y medio plazo (<5 años), siendo necesarias series temporales más largas. En este contexto, el objetivo general de esta tesis doctoral fue investigar los efectos a largo plazo de un incendio forestal en ríos mediterráneos. En concreto, esta tesis doctoral se centra en los efectos de dos legados del fuego: (1) la reducción de la cobertura del bosque de ribera y (2) la extinción local del superdepredador en estos ríos, Barbus meridionalis, un pez amenazado de pequeño tamaño. Los resultados de esta tesis doctoral probaron cómo el legado del fuego en el bosque de ribera aceleró la descomposición de la hojarasca en un arroyo mediterráneo intermitente ocho años después del incendio. Nuestros resultados también demostraron que el superdepredador era funcionalmente insustituible. Nuestro experimento de mesocosmos mostró que la ausencia de Barbus meridionalis provocó el incremento de los depredadores y de los consumidores primarios, y redujo la producción primaria del perifiton. El estudio de la ecología trófica de B. meridionalis desde una perspectiva funcional reveló que los rasgos morfológicos y de comportamiento de los macroinvertebrados pueden explicar su vulnerabilidad a la depredación. Esta tesis también confirmó que la ausencia del superdepredador modificó otra función clave del ecosistema, aceleró la descomposición de las hojas. Nuestros resultados también sugirieron que el superdepredador tiene un papel clave en el reciclado de nutrientes. Esta tesis doctoral ha demostrado que los incendios del pasado pueden influir en la estructura y función actual de los ríos mediterráneos. Además, también ha evidenciado que los ríos intermitentes pueden verse afectados por las consecuencias de la extinción de sus superdepredadores. La relevancia de esta tesis doctoral radica en el incremento esperado de los incendios forestales en la región mediterránea y en el alto riesgo de extinción de los peces de pequeño tamaño en los ecosistemas acuáticos continentales.

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Verkaik, Iraima. "Wildfire effects on macroinvertebrate communities in Mediterranean streams / Efectes dels incendis forestals sobre las comunitats de macroinvertebrats en rius Mediterranis." Doctoral thesis, Universitat de Barcelona, 2010. http://hdl.handle.net/10803/1450.

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Wildfire effects on macroinvertebrate communities have not been intensively studied in other areas than the Western US, and the results in fire prone areas like NE Mediterranean and SE Australia are scarce. In this study, Mediterranean streams (both fire affected and control) presented the highest dominance of r-strategy taxa, which are characterized by their high resilience. However, three years after fire, the indirect effects of the riparian canopy removal was still significant in these streams. Located in the same burned catchment, severely canopy affected area of the Vall d'Horta stream showed high aquatic vegetation cover compared to intact canopy cover, which showed, in turn, a high leaf litter cover percentage. Although differences in organic cover were significant in the macroinvertebrate community structure and turnover, hydrology was also a very important factor that marked the succession of communities along the year in both reaches. In the Mediterranean region, our studies conclude that midterm effects of fire on macroinvertebrate communities (up to 5 years) showed the importance of yearly precipitation in their response, and important differences in macroinvertebrate community dynamics were found depending if the year was wet or dry. We conclude that macroinvertebrate communities that live in Mediterranean climate streams showed in general high resilience to fire, because they usually have to cope with other severe disturbances like flooding and drought. The results obtained in this study indicate that other disturbances like droughts and floods can modulate the severity of the responses of the macroinvertebrate communities. In general, as in other biomes, post-fire precipitations are the most severe indirect effects where a large input of nutrients and dramatic habitat change takes place. In the Mediterranean catchments usually the big flood occurs few weeks after the wildfire, while in the other studied biomes the effects could be delayed by drought (SE Australia) or by the hydrologic characteristics from the stream itself (NW USA). Furthermore, if all these disturbances will come more often and together in the future, the presence of many species may be compromised, especially those that now are not found or found in low numbers in the dry years. Los efectos de los incendios forestales en las comunidades de macroinvertebrados han sido intensamente estudiados en el oeste de los Estados Unidos. Otras áreas donde el fuego es también un factor recurrente, como por ejemplo en el noreste del Mediterráneo y sureste de Australia, los estudios son muy escasos. En este contexto, el principal objetivo de este trabajo fue estudiar los efectos a mediano plazo de los incendios forestales sobre las comunidades de macroinvertebrados de los ríos mediterráneos y comparar los resultados con los de otros biomas. Después del incendio del 2003 que afectó el Parque Natural de Sant Llorenç en Cataluña se estudiaron las respuestas a corto y mediano plazo de las comunidades de macroinvertebrados de ríos en cuencas quemadas y cuencas establecidas como control. En general, las comunidades de macroinvertebrados (tanto de los ríos afectados por el fuego como los ríos control) presentaron un dominio de los taxones de estrategia "r", que caracteriza la frecuencia de perturbaciones de estos ríos y asimismo su alta resiliencia. Tres años después del incendio, los efectos indirectos del fuego se compararon en dos localidades de la Vall d'Horta afectadas de manera diferente en la cobertura de ribera. La eliminación del bosque de ribera generó diferencias significativas en la cobertura orgánica que a su vez fueron importantes para la estructura y temporalidad de la comunidad de macroinvertebrados. Sin embargo, la hidrología también fue un factor muy importante que marcó la sucesión de comunidades a lo largo del año. En este sentido, los efectos a mediano plazo después de un incendio forestal en las comunidades de macroinvertebrados (hasta 5 años) mostraron la importancia de la precipitación anual en su respuesta, y las mayores diferencias en la dinámica de la comunidad de macroinvertebrados se encontraron dependiendo de si el año había sido húmedo o seco. En conclusión, las comunidades de macroinvertebrados que estos ríos mediterráneos mostraron en general una alta resistencia al fuego, ya que por lo general tienen que hacer frente a otras perturbaciones comunes como las inundaciones y las sequías. La comparación de estos resultados con otros biomas indica que otras alteraciones como las sequías y las inundaciones pueden modular la severidad de las respuestas de las comunidades de macroinvertebrados. En general, como en otros biomas, las precipitaciones después de un incendio son los efectos indirectos más graves en un gran aporte de nutrientes y con el aumento de la erosión se genera un cambio dramático del hábitat. En las cuencas del mediterráneo por lo general la gran inundación post-incendio se produce pocas semanas después del incendio, mientras que en comparación con los otros biomas estudiados los respuestas podrían ser retrasadas por la sequía (sureste Australia) o por las características hidrológicas de los ríos (noroeste de los Estados Unidos). Se prevé que estas perturbaciones incrementarán tanto la recurrencia como la intensidad ya que ocurrirán al mismo tiempo, en este contexto la presencia de muchas especies y la resiliencia puede verse comprometida, sobre todo las que ahora no se encuentran o se encuentran en baja abundancia en los años secos.

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Ferreira, Mário Rui Mota. "Multi-species occupancy modeling of natural and anthropogenic habitats by mediterranean amphibians: grim prospects for conservation in irrigated farmland." Master's thesis, Universidade de Évora, 2012. http://hdl.handle.net/10174/10780.

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This study approaches the destruction of temporary ponds in an intensified agricultural landscape and the alternative breeding habitats for the amphibian community. We used several surveys to model the ponds survival since 1991 until 2009. Ponds inside the irrigation perimeter have a significant lower survival probability then those outside. Ponds, agricultural reservoirs, streams, irrigation channels and ditches were sampled for amphibian larvae in four different periods of a breeding season. We used a hierarchical dynamic occupation model that accounts for different detection probabilities to compare the occupation of aquatic habitats during the different periods. Ponds were the habitat with higher specific richness per site followed by streams and reservoirs. Ditches and irrigation channels, usually, only supports one species per site. All habitats, except for ponds, have high incidence of exotic predators (fish and crayfish), that explains, in part, the low specific richness of these sites. There’s no alternative habitat for the disappearing ponds. The conservation of the remaining ponds is essential for conserving the amphibian community. It should seriously be taken into consideration the construction of new clusters of ponds inside of the irrigation perimeter; Resumo: Este estudo aborda a destruição de charcos temporários numa paisagem agrícola em crescente intensificação, bem como possíveis alternativas para habitats de reprodução da comunidade de anfíbios. Cruzámos a informação de vários levantamentos para modelar a sobrevivência dos charcos de 1991 a 2009. Os charcos dentro do perímetro de rega tem a probabilidade de sobrevivência significativamente mais baixa que os charcos fora do perímetro. Foram amostrados as larvas de anfíbios em charcos temporários, charcas de rega, ribeiras, canais de rega e valas de drenagem em quatro períodos distintos de uma época de reprodução. Usámos um modelo hierárquico de ocupação dinâmica, com correcção para a detectabilidade para comparar a ocupação entre os habitats ao longo dos diferentes períodos. Os charcos temporários foram os habitats com maior riqueza específica por local, seguido pelas ribeiras e charcas de rega. Os canais e valas são habitats mais pobres, raramente suportando mais que espécie por local. A elevada incidência de predadores introduzidos (peixe e lagostins) em todos os habitats menos nos charcos pode explicar em parte a diferença de riqueza específica. Esta comunidade de anfíbios não tem uma alternativa viável para os charcos que continuam a desaparecer e a sua conservação passa pela conservação dos charcos que restam. Deverá ser considerado a hipótese da construção de novos complexos de charcos dentro do perímetro de rega.

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Arce, Sánchez María Isabel. "Retención de nitrógeno y procesos biogeoquímicos en ríos mediterráneos semiáridos : factores medioambientales implicados en su variación espacial y temporal= Nitrogen retention and biogeochemical processes in mediterranean semiarid streams : environmental factors involved in their spatial and temporal variation." Doctoral thesis, Universidad de Murcia, 2014. http://hdl.handle.net/10803/134885.

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En paisajes Mediterráneos semiáridos, las prácticas agrícolas, la escasez de agua y la salinidad natural de muchos suelos son, tanto directa como directamente, factores potenciales que pueden controlar la variación de la retención de nitrógeno (N) en ríos. De todos los procesos biogeoquímicos implicados en el ciclo del N, el proceso de desnitrificación es, en comparación, sumamente relevante ya que este proceso es el único capaz de eliminar N del ecosistema de forma permanente. Este proceso, mediado por microorganismos, convierte el nitrato (NO3-) en N gas. El objetivo general de esta tesis es examinar la retención de N en ríos Mediterráneos semiáridos e investigar los factores medioambientales que potencialmente pueden explicar su variación especial y temporal. Cuantificar tasas de desnitrificación y estudiar patrones en su variación, es esencial para entender el funcionamiento de los ríos como base para su manejo y gestión sostenible, especialmente en cuencas que están influenciadas por la agricultura, Por lo tanto, una parte importante de esta tesis de centra en entender como los factores citados arriba pueden impactar las tasas de desnitrificación en ríos. Adicionalmente, se evaluó la eficiencia y capacidad de retención de NO3- a escala de tramo de río, con el objetivo, además, de estimar la contribución del proceso de desnitrificación dentro de la retención total de un ecosistema fluvial. Se midieron la tasas de desnitrificación en sedimentos de varios ríos semiáridos de la provincial de la Cuenca Hidrográfica del Segura, incluyendo ríos afectados por agricultura, ríos temporales afectados por periodos naturales de sequía o estiaje y ríos naturalmente salinos. La desnitrificación se midió siguiendo el método de inhibición por Acetileno, una técnica ampliamente recocida en suelos y sedimentos. Paralelamente, se evaluó la retención de NO3- a escala de tramo de río en varios ecosistemas fluviales, usando técnicas de adición instantánea de nutrientes. Los resultados de esta tesis muestran que la desnitrificación en ríos semiáridos incrementa a lo largo de un gradiente de agricultura, principalmente en respuesta a las elevadas concentraciones de NO3- del agua asociadas a las actividades agrícolas. La recuperación de los procesos biogeoquímicos al re-humedecimiento tras la sequia y el tiempo en el cual las tasas alcanzan los niveles pre-estiaje, pueden depender de condiciones locales intrínsecas al ecosistema fluvial como i) la frecuencia natural de ciclos de intermitencia hídrica ii) del grado de desecación de los sedimentos durante el estiaje y iii) otros factores diferentes al hidrológico que puedan modular las funciones microbianas, como los niveles de nutrientes en el agua. A pesar de que las tasas de desnitrificación tendieron a ser elevadas, su contribución a escala de tramo en la retención global de NO3– en ríos semiáridos fue mínima (≤ 2.16%). Mecanismos alternativos a la desnitrificación, como la asimilación por parte de organismos heterótrofos y la reducción desasimilatoria del NO3– a NH4+ podrían tener un importante papel en la función que tienen los ríos semiáridos, de controlar los flujos de NO3–, especialmente los de agua salina. La salinidad del agua en un gradiente de 0.5 a 13 mS cm-1 no parece ejercer ningún papel en la variación de las tasas de desnitrificacion y de la retención de NO3– a escala de tramo. Sin embargo, bajo condiciones favorables para la desnitrificacion; buena disponibilidad de NO3– y carbono y bajos potenciales redox, valores de salinidad en torno a 40 mS cm-1 puede llegar a afectar negativamente a este proceso. In Mediterranean semiarid landscapes, agricultural activities, natural water scarcity periods and high salinity of soils are, both directly and indirectly, potential drivers on stream nitrogen (N) processing variation. Among all biogeochemical processes involve in N cycling, denitrification is the only mechanism that removes N permanently from the ecosystem. This pathway is microbially mediated and converts nitrate (NO3-) into N gas under anaerobic conditions. The overarching goal of this dissertation is to examine in-stream N processing in Mediterranean semiarid streams and environmental drivers potentially involved in its spatial and temporal variation. Quantifying stream dentirification rates and studying patterns in their variation are essential to understand the fundamental functioning of temporary streams as a basis for sustainable management, especially in agriculturally affected catchments. Therefore, an important part of this thesis sought to deepen in the understanding of how the aforementioned factors impact on denitrification rates. Denitrification was measured in sediments from several semiarid streams located in the Segura Catchment, including agriculturally affected, temporary o naturally affected by dry periods, and naturally saline. Denitrification was measured using the Acetylene blockage method, a technique widely used in soils and sediments. In parallel, NO3- retention at whole-reach level was also examined in several streams using nutrient pulse additions to investigate the stream capacity to take up additional NO3- and to quantify the contribution of denitrification to the whole-stream retention As widely described in other climatic regions, the results of this thesis indicated that denitrifcation rates in semiarid streams increases following the gradient of increased agricultural influence, mostly in response to high water NO3– concentrations. The recovery of biogeochemical processes' capacity following rewetting of dry sediments, and time in which rates return to pre- drought levels likely depend on the local conditions associated to each stream ecosystem such as i) the dry-wet cycles history, ii) the grade of sediment desiccation during drought and iii) another streams factors driving microbial activities, such as nutrient status. Despite denitrification rates tended to high, in the upper part of the reported range in stream literature, the potential contribution of denitrification to whole-reach NO3 uptake was minimal (≤ 2.16%). Alternative pathways to denitrification, heterotrophic assimilation and dissimilatory NO3– reduction to NH4+ can have a substantial influence on modifying NO3– fluxes in semiarid saline streams. Water salinity in a range of 0.5 to 13 mS cm-1 appears not to be involved in the spatial variation of denitrification rates and whole-reach NO3– uptake. However, salinity values close to 40 mS cm-1 can constraint denitrification rates once no one factor, such as NO3– and redox, limits the mechanisms.

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Sarremejane, R. (Romain). "Community assembly mechanisms in river networks:exploring the effect of connectivity and disturbances on the assembly of stream communities." Doctoral thesis, Oulun yliopisto, 2018. http://urn.fi/urn:isbn:9789526218632.

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Abstract Community assembly results from a combination of deterministic and stochastic mechanisms, whose relative effects can vary in response to environmental heterogeneity, connectivity, disturbance regimes and anthropogenic stressors. Understanding how community assembly mechanisms vary in response to environmental changes and connectivity is crucial for the management and conservation of river ecosystems. In this thesis, I tested the effects of connectivity and natural flow disturbances on riverine invertebrate communities by assessing assembly mechanism changes in response to (I) habitat connectivity, (II) seasonal flow intermittency and (III) inter–annual hydrological variability. I also conducted a field experiment to test for (IV) the effects of human–induced nutrient enrichment on community assembly of microorganisms (diatoms and aquatic fungi) and stream ecosystem functioning under different environmental settings. Invertebrate community assembly changed gradually with habitat connectivity. While limited dispersal resulted in higher community variability in the most isolated streams, mass effects caused community homogenization in the most connected ones. Natural and human induced disturbances lead to changes in the relative importance of deterministic and stochastic factors but often through different, or even opposite, mechanisms depending on the natural background of the ecosystem and organism type considered. For instance, seasonal drying and high–flow periods in intermittent Mediterranean rivers promoted deterministic and stochastic assembly processes respectively, whereas environmental sorting and stochastic processes respectively dominated during high and low flow years in boreal streams. Diatom and fungal communities responded differently to nutrient enrichment, with detrital processes and fungal communities responding more in naturally acidic than in circumneutral streams. The results of this thesis highlight the complexity of community assembly mechanisms: they tend to be highly context dependent and temporally variable. Therefore, stream bioassessment and conservation will benefit from explicitly incorporating connectivity and natural disturbance regimes. Assessing the interactive effects of connectivity and disturbances at the river network scale would provide a greater understanding of community assembly mechanisms and river ecosystem functioning Tiivistelmä Eliöyhteisöjen koostumus heijastelee determinististen ja stokastisten mekanismien vuorovaikutusta. Niiden suhteellinen merkitys vaihtelee suhteessa yhteisöjen kytkeytyneisyyteen sekä luontaisiin ja ihmisen aiheuttamiin häiriöihin. Yhteisöjen säätelymekanismit vaihtelevat jokiverkoston eri osissa ja tietoa tästä vaihtelusta tarvitaan jokiekosysteemien hoidon kehittämiseksi. Tässä tutkielmassa testasin elinympäristöjen kytkeytyneisyyden ja luontaisten häiriöiden (virtaamavaihtelut) vaikutuksia jokien selkärangatonyhteisöihin. Suoritin myös kenttäkokeen, jossa testattiin ihmisen aiheuttaman rehevöitymisen vaikutuksia mikro–organismeihin (piilevät, mikrobit) ja ekosysteemitoimintoihin erilaisissa ympäristöoloissa (luontaisesti happamat vs. neutraalit purot). Selkärangattomien yhteisökoostumus muuttui asteittain jokiverkostossa. Yhteisökoostumuksen vaihtelu oli suurinta eristäytyneimmissä latvapuroissa, kun taas isommissa, uomaston keskivaiheilla sijaitsevissa koskissa voimakas levittäytyminen eri suunnista (ns. massatekijät) aiheutti yhteisöjen rakenteen homogenisoitumista. Kuivuusjaksot ja niitä seuraavat korkean virtaaman jaksot edistivät determinististen prosessien merkitystä Välimeren alueen joissa, kun taas boreaalisissa puroissa Pohjois–Suomessa äärevät virtaamaolot, erityisesti poikkeuksellisen kuivat kesät, edistivät satunnaismekanismien vaikutusta. Perustuottajat (piilevät) ja hajottajat (akvaattiset sienet) vastasivat eri tavoin ravinnelisäykseen. Sienten hajotustoiminta nopeutui ravinnelisäyksen myötä, mutta vain luontaisesti happamissa puroissa. Tämän opinnäytetyön tulokset korostavat yhteisön kokoonpanomekanismien monimutkaisuutta: ne ovat usein erittäin tilanneriippuvaisia ja ajallisesti vaihtelevia. Siksi jokien ekologisen tilan arvioinnissa tulisi huomioida tutkimuspaikkojen kytkeytyneisyys jokimaisemassa

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Sanpera, Calbet Isis. "Global changes in headwater streams: effects of hydrological and nutrient fluctuations on the quality of basal resources = Canvis globals en rius de capçalera: efectes de les fluctuacions hidrològiques i dels nutrients en la qualitat dels recursos basals." Doctoral thesis, Universitat de Barcelona, 2014. http://hdl.handle.net/10803/145433.

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Streams are complex and highly diverse ecosystems. Within the stream network, headwater streams (1st to 3rd order) are highly important. Headwaters represent most of the total length, influence the structure and functioning of higher order streams, generate most of the water flow and support higher rates of biogeochemical processing, with a higher rate of nutrient removal. Moreover, they offer high habitat diversity, both within and among streams. From all the drainage basin, it is the riparian zone which has the greatest influence in the structure and functioning of these streams. The in-fall of vegetation and leaching from plant litter are major sources of energy for stream food webs. All energy available to consumers originates from primary producers from either out- or in-stream and food webs are fuelled by a complex mixture of allochthonous and autochthonous resources. In headwaters, allochthonous basal resources are generally larger than autochthonous energy sources. However, both the quantity and quality of allochthonous and autochthonous resources influence the stream structure and functioning. Quality of resources determines their potential nutritional value for the invertebrates feeding on them. The nutritional quality of organic matter (OM) can be assessed by measuring the elemental or biomolecule composition (polysaccharide, protein and lipid content). Lipids are the most efficient energy-storing compounds, and within lipids, fatty acids and sterols include essential molecules for consumers. In a context of global change, streams are highly affected by multiple direct and indirect anthropic impacts, such as climate change, land use changes and water course alterations, affecting hydrology and nutrient and light availability, which in turn affect the quality and quantity of basal resources. The aim of this thesis was to determine how environmental factors influence the quantity and quality (biochemical composition) of basal resources in headwater streams. Of the multiple environmental factors affected by global change, the present study focused on changes in hydrology and nutrient and light availability, with particular reference to headwater Mediterranean streams. This study has been mainly performed in Fuirosos, a Mediterranean stream in the northeast of the Iberian Peninsula, but also in the Mayfly creek artificial channels, in the Pacific Coast Mountains of Canada. Several methods were used, such as the measure of particulate and dissolved OM fluxes, elemental composition of OM, nutrient addition; chlorophyll content, bacterial density and extracellular enzymatic activities of biofilms, and the measurement of the biochemical quality of the basal resources. (i.e., epilithic and epipsammic biofilms, leaves and, transported particulate and dissolved OM). We have demonstrated that the El Niño Southern Oscillation (ENSO) affected riparian inputs to the stream through teleconnections that alter average precipitation (during El Niño periods, average annual precipitation was lower than in other periods, causing higher riparian inputs, due to the hydric stress of riparian trees while, during La Niña periods, precipitation was higher than at other times, leading to decreased riparian inputs). Drought periods caused a bimodal distribution of annual riparian inputs and reduced the quality of basal resources, whereas accumulated drought events diminished the riparian inputs. Floods decreased the benthic OM, increased the amount of transported OM and modified its quality. The addition of nutrients led to a decrease in carbon content, and higher light availability led to a decrease in protein content of allochthonous resources. Biofilm quality was generally higher with the addition of nutrients when light availability was higher. We consider that the nutritional quality of basal resources is a complex parameter. Whilst elemental and biochemical composition can sometimes be related, knowledge on the latter enables a better understanding of the mechanism by which abiotic changes affect the quality of resources. However, the complexity of measuring elemental composition, biochemical composition and fatty acid composition gradually increases. Hence, we suggest that the choice of the indicators of quality used would depend on the goal of the study that want to be performed and on the trade-off between analysis effort and information that wants to be obtained. Because food webs are fuelled by a complex mixture of allochthonous and autochthonous resources, the quantity and quality of these resources are limiting factors for stream secondary production. Hence, the changes observed in this study, will probably affect stream food webs. Els rius són ecosistemes complexes i molt diversos. Dins la xarxa fluvial, les rius de capçalera (de 1er a 3er ordre) tenen una gran importància. Els rius de capçalera representen la major part de la longitud total, influencien l’estructura i el funcionament dels rius d’ordre més gran, generen la major part del cabal i donen suport a taxes altes de processament biogeoquímic, amb una alta taxa d’eliminació de nutrients. A més a més, contenen un gran diversitat d’hàbitats, tant dins dels rius com entre ells. De tota la conca, és la zona ripària la que té una més gran influència en l’estructura i el funcionament d’aquests rius. La caiguda de la vegetació i el lixiviat de les fullaraca són importants fonts d’energia per les xarxes tròfiques. Tota l’energia disponible pels consumidors prové dels productors primaris tant de dins com de fora del riu i les xarxes tròfiques estan sustentades per una complexa barreja de recursos al•lòctons i autòctons. En els rius de capçalera, els recursos basals al•lòctons són generalment més importants que les fonts d’energia autòctones. Tot i això, tant la quantitat com la qualitat dels recursos al•lòctons i autòctons influencies l’estructura i el funcionament d’aquests rius. La qualitat dels recursos determina el seu valor nutritiu potencial pels invertebrats que s’alimenten d’ells. La qualitat nutritiva de la matèria orgànica (MO) es pot ser avaluada mesurant la composició elemental o de biomolècules (contingut de polisacàrids, proteïnes i lípids). Els lípids són els components d’emmagatzematge d’energia més eficients, i dins dels lípids, els àcids grassos I els esterols inclouen molècules essencials pels consumidors. En un context de canvi global, els rius estan afectats de forma molt important per múltiples impactes antròpics directes i indirectes, tals com el canvi climàtics, els canvis d’usos del sòl i les alteracions dels cursos fluvials; els quals afecten la hidrologia i la disponibilitat de nutrients i llum, els quals al seu torn, afecten la quantitat i la qualitat dels recursos basals en els rius de capçalera. Dels múltiples factors ambientals afectats pel canvi global, aquest estudi es centra en els canvis en la hidrologia i la disponibilitat de llum i nutrients, en particular als rius de capçalera Mediterranis. Aquest estudi ha estat realitzat principalment a Fuirosos, un riu Mediterrani al nord-est de la Península Ibèrica, però també als canals artificials de Mayfly creek, a les muntanyes de la costa Pacífica de Canadà. En aquest estudi s’han utilitzat diversos mètodes, tal i com la mesura dels fluxos de MO particulada i dissolta, la composició elemental de la MO, l’addició de nutrients; el contingut de clorofil•la, la densitat bacteriana i les activitats enzimàtiques extracel•lulars del biofilm i la mesura de la qualitat bioquímica dels recursos basals (és a dir, els biofilms epilítics i epipsàmics, les fulles i la MO particulada i dissolta transportada). Hem demostrar que El Niño/Oscil•lació del Sud (ENOS) va afectar les aportacions ripàries al riu a través de teleconnexions que van alterar la precipitació mitjana (durant els períodes de El Niño, la precipitació mitjana anual era més baixa, provocant un augment de les aportacions ripàries, degut a l’estrès hídric dels arbres, mentre que durant els períodes de La Niña, la precipitació era més alta que en altres moments, portant a una disminució de les aportacions ripàries). Els períodes de sequera van causar una distribució bimodal de les aportacions ripàries anuals i van reduir la qualitat dels recursos basals, mentre que els episodis de sequera acumulats van provocar la disminució de les aportacions ripàries). Les avingudes van provocar la disminució de la MO bentònica, van augmentar la quantitat de MO transportada i van modificar la seva qualitat. L’addició de nutrients va portar a una disminució del contingut de carboni, i una disponibilitat més alta de llum va provocar una disminució del contingut de proteïnes dels recursos al•lòctons. La qualitat del biofilm era generalment més alta amb l’addició de nutrients quan la disponibilitat de llum era més alta. Considerem que la qualitat nutritiva dels recursos basals és un paràmetre complex. Tot i que la composició elemental i bioquímica poden estar relacionades en alguns casos, el coneixement d’aquesta última permet una millor comprensió dels mecanismes a través dels quals els canvis abiòtics afecten la qualitat dels recursos. Tot i això, la complexitat de mesurar la composició elemental, la composició bioquímica i els àcids grassos, augmenta gradualment. Així doncs, suggerim que la tria dels indicador de qualitat utilitzats dependrà de l’objectiu de l’estudi que es vulgui realitzar i en el balanç entre l’esforç d’anàlisi i la informació que es vol obtenir. Com que les xarxes tròfiques estan sustentades per una complexa barreja de recursos al•lòctons i autòctons, la quantitat i la qualitat d’aquests recursos són factors que limiten la producció secundària en el riu. Així doncs, els canvis observats en aquest estudi, afectaran probablement les xarxes tròfiques fluvials.

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Machowetz, Anja. "Untersuchung kardioprotektiver Wirkungen des Olivenöles und seiner phenolischen Komponenten in einer Gruppe gesunder deutscher Männer." Phd thesis, Universität Potsdam, 2006. http://opus.kobv.de/ubp/volltexte/2006/1043/.

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"Untersuchung kardioprotektiver Wirkungen des Olivenöles und seiner phenolischen Komponenten in einer Gruppe gesunder deutscher Männer" EINLEITUNG: Epidemiologische Daten belegen, dass die mediterrane Ernährung mit einer niedrigen Inzidenz an mit oxidativen Stress assoziierten kardiovaskulären Erkrankungen einhergeht. Dabei wird vor allem dem Olivenöl, als Hauptfettlieferant in der mediterranen Ernährung, eine kardioprotektive Wirkung zugesprochen. Olivenöl zeichnet sich neben dem hohen Gehalt an einfach ungesättigten Fettsäuren (MUFA) durch ein reichhaltiges Spektrum an phenolischen Verbindungen aus, deren antioxidative Wirkung bereits zahlreichen in in vitro Studien beschrieben wurde. Demnach könnte der Verzehr von phenolreichem Olivenöl auch in vivo vor oxidativen Schädigungen schützen und somit das Risiko für kardiovaskuläre Erkrankungen senken. ZIELSTELLUNG: Untersuchung der kardioprotektiven Wirkung von Olivenöl und seiner phenolischen Komponenten in einer Gruppe gesunder deutscher Männer. METHODE: Dazu wurde eine randomisierte cross-over doppelt-verblindete Interventionsstudie an 70 gesunden Männern zwischen 20 - 60 Jahren im Raum Berlin-Brandenburg durchgeführt. In jeweils drei dreiwöchigen Interventionsphasen konsumierten die Probanden täglich 25 ml natives (phenolreich), gemischtes (mittlerer Phenolgehalt) und raffiniertes (annähernd phenolfrei) Olivenöl, was sich ausschließlich im Gehalt an phenolischen Verbindungen unterschied. Das Olivenöl sollte dabei die gewöhnlich verzehrten Fette ersetzen. Die Interventionsphasen waren durch zweiwöchige Wash out-Phasen unterbrochen. Die Erhebung der Blutlipide, Biomarker der Lipidperoxidation und endogene Antioxidantien erfolgte zu Studienbeginn sowie zu Beginn und Ende jeder Verzehrsperiode. ERGEBNISSE: Bei den Blutlipiden sowie den Biomarkern der Lipidperoxidation und den endogenen Antioxidantien konnte keine signifikante Veränderung in Abhängigkeit vom Phenolgehalt der applizierten Olivenöle nachgewiesen werden. Einzig die Glutathion-Reduktase-Aktivität stieg mit zunehmendem Gehalt an phenolischen Verbindungen (pTrend = 0,041). Unabhängig von der Konzentration der Phenole im Olivenöl wurde bei den Probanden durch den Olivenölverzehr eine Senkung von Gesamtcholesterol (p = 0,007) und Triglyzeride (p = 0,013) im Serum erzielt. Diese Wirkung geht einher mit einem gestiegenen MUFA-Anteil in der Ernährung aufgrund des Olivenölkonsums (p < 0,001). SCHLUSSFOLGERUNG: Die Hypothese, dass die Phenole im Olivenöl aufgrund ihrer in in vitro und Tierstudien beschriebenen antioxidativen Wirkung dem Olivenöl neben dem einzigartigen Fettsäureprofil eine zusätzliche kardioprotektive Wirkung bescheren, konnte in der vorliegenden Studie nicht gezeigt werden. Dennoch konnte durch den Olivenölverzehr und der damit einhergehenden Erhöhung des MUFA-Anteils in der Ernährung eine vorteilhafte Beeinflussung der Blutlipide erzielt werden. Obgleich Olivenöl nicht das vorwiegend verzehrte Fett in Deutschland darstellt, zeigten die befragten Probanden eine hohe Akzeptanz. Folglich könnte die Integration von Olivenöl in die habituelle Ernährung einen Beitrag zur Senkung des kardiovaskulären Erkrankungsrisikos leisten. "Cardioprotective effects of olive oil and its phenolic compounds in healthy German men" BACKGROUND: Epidemiological data show that the Mediterranean diet is related to a low incidence of oxidative stress associated cardiovascular diseases. In particular, olive oil, which is the most consumed alimentary fat in the Mediterranean diet, is discussed to be cardio protective. Besides its high monounsaturated fatty acid content olive oil contains a remarkable amount of phenolic compounds. Results from in vitro and animal studies suggest that these phenols are powerful antioxidants. Thus, consumption of olive oil phenols also could inhibit oxidative damage in vivo and therefore could reduce the risk of cardiovascular diseases. OBJECTIVE: To investigate the cardioprotective effect of olive oil and its phenolic compounds in healthy German men. METHODS: Therefore, a randomised, cross-over, double-blind intervention trial in 70 healthy men aged 20 - 60 years from the Berlin-Brandenburg area was conducted. Subjects were randomised for three periods of three weeks to replace their usually consumed fat by daily 25 ml of virgin (high-phenolic), common (medium-phenolic) and refined (low-phenolic) olive oil, which vary only in their content of phenolic compounds. Each intervention was separated by a two-week wash-out period. Blood lipids, lipid peroxidation biomarker and endogenous antioxidants were assessed at study baseline and the beginning and end of each intervention period. RESULTS: In the total study population, blood lipids, biomarker of lipid peroxidation and endogenous antioxidants were not affected by the phenolic content of the olive oils administered. Solely, a concentration-dependent increase in glutathion-reductase activity could be observed (pTrend = 0.041). A significant reduction in serum total cholesterol (p = 0.007) and triglycerides (p = 0.013) after of olive oil consumption was assessed, which was independent from the content of phenolic compounds in the olive oil. This effect goes along with an increased monounsaturated fatty acids proportion in the habitual diet of the subjects as a result of the olive oil consumption (p < 0.001). CONCLUSION: The hypothesis, that phenolic compounds in olive oil due to its antioxidative properties reported in in vitro and animal studies provide additional cardioprotective effects besides those attributed to its unique fatty acids profile could not be supported by this study. However, olive oil consumption exert beneficial effects on blood lipids, which could be ascribed to the increased monounsaturated fatty acid content in the diet. Even though olive oil is not the main source of fat in Germany, the interviewed participants showed a high acceptance. Thus, integration of olive oil into the habitual diet could contribute to a risk reduction in cardiovascular diseases among German men.

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Scalici, Giovanni. "Physiological and productive responses of Miscanthus genotypes to different climatic constraints in Mediterranean environment." Doctoral thesis, Università di Catania, 2014. http://hdl.handle.net/10761/1603.

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Strong global growth and development has increased demand for energy to refine, manufacture and transport products to support the lifestyles of an increasingly developing and globalized world. In recent decades, fossil fuels have become important sources of energy. However, with increasing demand, there has been developing concern over the sustainability of fossil fuels relating to their potential future sources and harmful byproducts of use, specifically large net carbon releases, which has spurred interest towards the use of alternative renewable energy sources. Potential alternatives are available including wind, solar, hydro, and biomass, all of which are touted to have greater environmental benefits relative to fossil fuels. There has been increasing interest in the use of perennial grasses as energy crops in the US and Europe since the mid-1980s. The characteristics which make perennial grasses attractive for biomass production are their high yield potential, the high contents of lignin and cellulose of their biomass and their generally anticipated positive environmental impact. For this purpose, three different researches were carried out with the aim of studying i) the adaptation and biomass production potential of 18 Miscanthus accessions, representing 5 Miscanthus species, collected from a wide geographical range (Numata, 1974) for suitability to semi-arid Mediterranean climates; ii) the effect of harvest time (autumn and winter time) on biomass yield, morph-biometric characters, moisture content, cellulose, hemicelluloses and lignin contents for second generation bioethanol production and ash content for combustion purposes in a long term plantation of Miscanthus x giganteus in a Mediterranean environment; iii) the effect of heat stress, in controlled-environment, on 5 Miscanthus genotypes, coming from the Miscanthus germplasm collection at Institute of Biological, Environmental and Rural Sciences (IBERS) of the Aberystwyth University Wales UK, to identify if the high temperature have a negative effect on the growth, partitioning and physiology of Miscanthus plants. Results suggest that some Miscanthus accessions are suitably adapted to maintain high biomass in a semi-arid Mediterranean environment and that the most commonly available commercial Miscanthus genotypes (M. x giganteus and Goliath) are not well adapted to the Mediterranean climate or environments where water is a limiting factor, and there are other Miscanthus accessions that produce high biomass in water limited semi-arid regions. Long term Miscanthus plantations strictly depend by the thermopluviometric trend of the growing season, decreasing biomass yield as rainfall reduces and the biomass for specific end uses presents higher quality (in terms of more hemicellulose and cellulose content than ash content), with winter harvest. Relative to low temperature, high temperature decreased the plant height (~48%), above-ground dry biomass (~66%), below-ground dry biomass (~26%) and photosynthetic response to absorbed light (~13%). The most widely available and commonly used variety of Miscanthus is sensitive to high temperatures and there are other genotypes that have a higher capacity for carbon assimilation in high temperature environments.

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Lupón, i. Navazo Anna. "The influence of Mediterranean riparian zones on stream nitrogen dynamics: A catchment approach." Doctoral thesis, Universitat de Barcelona, 2015. http://hdl.handle.net/10803/350313.

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Riparian areas are recognized to be natural filters of nitrogen (N) because they can substantially diminish the N delivery from terrestrial to aquatic ecosystems. However, understanding the influence of riparian zones on regulating N export from catchments is still challenging, mainly because stream water chemistry integrates biogeochemical processes co-occurring within upland, riparian, and fluvial ecosystems. The present dissertation aims to explore the influence of Mediterranean riparian zones on regulating both stream hydrology and catchment N exports, by combining empirical and modelling approaches at different temporal and spatial scales. Findings obtained from plot experiments show that the studied Mediterranean riparian soils acted as hot spots of soil microbial N supply within the catchment because they exhibited considerably higher net N mineralization (NNM) and net nitrification (NN) rates than upland oak and beech soils. This difference was attributed to larger stocks of N-rich leaf litter and permanent moist conditions in the riparian soils. Furthermore, soil microbial processes in the riparian site showed a distinct climatic sensitivity than in upland sites, which ultimately led to different temporal patterns of soil N cycling. Soil moisture was the major driver of NNM and NN in upland forests, while both temperature and precipitation shaped soil N dynamics in the riparian zone. Therefore, both upland and riparian soils exhibited pulses of NNM and NN following spring rewetting events, though summer temperatures only stimulate microbial activity at the riparian site. Riparian microbial pulses contributed > 25% to annual rates of NNM and NN; and coincided with increases in stream N loads. These results suggest that Mediterranean riparian soils may become important sources of nitrate (NO3-) to streams under future warming scenarios. Additionally, findings obtained from catchment-scale studies show that our Mediterranean riparian zone exerted a strong control on stream hydrology during the vegetative period. Riparian evapotranspiration (ET) influenced the temporal pattern of stream discharge and riparian groundwater elevation across daily and seasonal scales. Further, the influence of riparian ET on stream hydrology increased from headwaters to the valley bottom, where stream hydrological retention was prominent. Nonetheless, such stream hydrological retention wasn’t accompanied by a decrease in catchment N exports, likely because low flow conditions, relatively warm conditions, and large stocks of N-rich leaf litter within the streambed enhanced in-stream NO3- release in summer. Conversely, in-stream photoautotrophic NO3- uptake was the major controlling factor of stream N dynamics in spring, when high light inputs favored gross primary productivity (GPP) prior to riparian canopy closure. As it occurred for summer nitrification, the influence of GPP on stream N dynamics increased along the stream continuum. At the valley bottom, in-stream photoautotrophic activity drop midday stream N concentration by 13% and reduced catchment NO3 exports by 10%. Finally, during the dormant period, we found minimal evidences of either NO3 uptake or release in the riparian zone. Mass balance calculations at the whole-reach scale showed that both riparian groundwater inputs and in-stream processes contributed to longitudinal changes in stream NO3 concentrations, and thus, both sources of variation were necessary to understand stream water chemistry along the stream. Together, these results suggest that the high bioreactivity of streams ecosystems can influence stream N dynamics at the catchment scale, and even screen the potential buffer capacity of riparian zones as observed for this Mediterranean catchment. Overall, findings gathered in the present dissertation question the idea that Mediterranean riparian zones are efficient N buffers, and stress that an integrated view of upland, riparian, and stream ecosystems is essential for advancing our understanding of catchment hydrology and biogeochemistry. Durant l'última dècada, les activitats antropogèniques han doblat el nitrogen disponible, provocant nombrosos problemes ambientals. En un context de conca, els boscos de ribera tenen la capacitat de reduir els excessos de nitrogen que els hi arriben dels ecosistemes terrestres adjacents i, per tant, poden ser fonamentals per determinar la concentració de nitrogen al riu i l'exportació d'aquest nutrient aigües avall. L'objectiu d'aquesta tesi és analitzar la influència dels boscos de ribera sobre els recursos hídrics i la dinàmica del nitrogen en una conca mediterrània. Durant l'estudi, els sòls de ribera exhibiren unes taxes netes de mineralització i nitrificació clarament superiors als boscos de capçalera (alzinar i fageda), les quals foren atribuïdes als estocs de fullaraca i a l'alta humitat dels sòls riparians. A més, els sòls de ribera foren importants fonts de nitrat al riu, especialment quan les altes temperatures o les fortes precipitacions provocaren pics d'activitat microbiana que contribuïren > 25% en termes anuals. Hidrològicament parlant, la vegetació ripariana tingué un paper clau sobre els recursos hídrics de la conca, perquè regulà el cabal fluvial a diferents escales temporals, i promogué la pèrdua d'aigua del riu cap a la ribera en el fons de vall. Tanmateix, la ribera no retingué nitrogen durant el període de retenció hidràulica, així com tampoc durant la resta de l'any. Per contra, el baix cabal i les altes temperatures incentivaren la nitrificació a la llera del riu durant l'estiu. A més, durant la primavera, l'augment de llum previ al desenvolupament de la capçada de ribera afavorí la producció primària bruta en el riu, la qual provocà clares fluctuacions diàries en les concentracions de nitrat i reduí un 10% les exportacions d'aquest nutrient aigües avall. Conjuntament, els resultats d'aquesta tesi no només qüestionen la idea que les zones de ribera són filtres naturals de nitrogen en regions mediterrànies, sinó que manifesten la importància d'una visió integradora de tots els components del paisatge per tal per tal d'avançar en el nostre coneixement sobre la hidrologia i la biogeoquímica a escala de conca.

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Ramos, de Fuentes Eduardo. "Developing of new stress-tolerant rice varieties for the Mediterranean region." Doctoral thesis, Universitat de Barcelona, 2018. http://hdl.handle.net/10803/663479.

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Rice (Oryza sativa) is the most important crop for human direct consumption, but its yield and production are strongly affected by biotic and abiotic stresses. Rice is the most salt-sensitive cereal and in addition, salinity is a rising problem around the world reinforced by the climate change effects such as rise of the sea level, soil degradation and water scarcity. Regarding biotic stresses, the apple snail (Pomacea sp.) is one of the worst introduced pest that affects rice production. It has been detected for first time in Europe in Spain, in 2009 in Ebro River Delta, destroying rice fields at seedling stage. Additionally, rice blast, caused by an ascomycete called Pyricularia oryzae, is a disease that strongly affects the rice production worldwide causing yield losses that range from 15% to 50%, even using specific fungicides. The main objective of this thesis is to develop new stress-tolerant rice varieties for the Mediterranean region, by the introgression of the Saltol QTL and new blast resistance genes to Mediterranean local varieties. A molecular marker assisted backcross scheme (using KASP technology) was followed to introgress the salt tolerance traits. The Saltol donor varieties were FL478 and IR64-Saltol, two salt-tolerant Asiatic indica rice lines, while the recurrent parental lines were PL12 and PM37, two Mediterranean japonica rice lines. BC3F3 plants were tested for salt tolerance in hydroponic assays. The standard evaluation system (SES) described by IRRI was used to evaluate the lines. Relative chlorophyll content (RCC, measured with a SPAD), fresh weight and plant length was also recorded. Additionally, two consecutive years of field assays were performed in Ebro River Delta using different foreign and local lines (and their hybrids), to evaluate their general performance and rice blast resistance. From the 4 crosses combination performed between both Saltol donors and both Mediterranean recurrent parents, PL12 x FL478 (LP cross) and PM37 x IR64-Saltol (MS) were selected to proceed with the whole backcrossing process, to determine the return to the recurrent parent genome and to obtain the homozygous Saltol BC3F4 seeds. For the hydroponic assays, 54 BC3LPF3 lines were initially tested since a high variability between lines was observed. From them, some lines like LP-3, LP-15 or LP-17, performed similar or even better in the SES than the salinity donor FL478 line. The RCC data showed again a high variability between lines, although RCC did not correlate with SES results. The data analysis was hindered due to the differences scored between replicates and the fact that much of them were totally dead at the end of the assay. A certain degree of heterozygosity may explain the variability found between replicates during the SES evaluation. The fresh weight (FW) and the plant length in both shoot and root was strongly affected by the salinity treatment. However, the reduction was higher in shoot than in root. Finally, the blast tolerance field assays were severely affected by the rice stem borer Chilo suppressalis, both years. The evaluation for rice blast tolerance was really difficult and no outstanding line was selected to proceed. In conclusion, the Saltol QTL has been successfully introgressed in two Mediterranean japonica rice varieties, although more replicates of the hydroponics assays must be performed to confirm and select the most salt tolerant obtained lines. These lines will be tested in 2018 and 2019 in field assays, under salinized and no salinized conditions. Regarding rice blast resistance field assays, no conclusive results were achieved. More field assays must be done, and other lines should be tested. In order to reduce C. suppressalis infestations, more phytosanitary actions should be taken in the future.

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Gonçalves, Ana Raquel Calapez. "Multiple-stressor impacts on mediterranean stream communities: responses to water scarcity and water pollution." Doctoral thesis, ISA, 2020. http://hdl.handle.net/10400.5/21198.

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Doutoramento em Restauro e Gestão Fluviais - Instituto Superior de Agronomia / Faculdade de Arquitetura / Instituto Superior Técnico. Universidade de Lisboa Freshwater ecosystems are influenced by diverse anthropogenic stressors and natural disturbances producing interacting effects (synergies and antagonisms) often unpredicted based on their independent effects, and thereby represent a major concern to predict ecological changes and develop effective management and restoration strategies. The aim of this Thesis was to assess different responses of key stream biological elements (i.e., biofilms and macroinvertebrates) to the impact of main stressors acting in concert in Mediterranean rivers related with water scarcity and pollution (i.e., flow velocity reduction/stagnation and sewage contamination/hypoxia), using mesocosm approaches and evidences of a case study. In a first part, the effects of flow reduction and oxygen depletion conditions in two seasons were evaluated in macroinvertebrates behavioural and functional responses, conducting to evidences of changes in drift patterns and loss of trait diversity with potential impacts on ecosystem functioning and services. In a second part was investigated how single and combined effects of water flow stagnation and sewage contamination affect primary producers and primary consumers, showing that while stagnant water had an overall inhibitory effect, sewage inputs increased biological responses. Also, stressors combined effect revealed to be unfavourable for some biofilm assemblages (decreasing bacteria and algae diversity) while advantageous to other (increasing fungi diversity). In the last part, flow and water quality variations were followed over time in a Mediterranean urban stream, leading to observations of an impoverished community with low diversity and high abundance of tolerant taxa and resistance traits, which was associated with multiple-stressors patterns of urban ecosystems. Overall it was showed that the effects of representative multiple-stressor scenarios on Mediterranean stream biota are dependent on water scarcity conditions and that reductions on sewage inputs needs to be given priority by stream managers to prevent further degradation of these aquatic ecosystems N/A

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Iuffrida, Letizia. "Transcriptional profiles inferring thermal stress responses of scleractinian corals from Mediterranean Sea." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/20374/.

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Shallow-water corals of the Mediterranean Sea are facing a dramatic increase in water temperature due to climate change. In many cases, a shift toward environmental conditions outside the normal range of variability may cause suboptimal physiological performance, such as enhanced respiration, higher susceptibility to pathogens, bleaching, reduced calcification and tissue necrosis. However, not all corals are thought to be affected equally, because physiological performances and responses are the principal determinant of a species tolerance to environmental variability and may change the ability of corals to cope with changing conditions. In this study, transcriptional profiles of four genes involved in apoptosis (bax and bcl-2), redox regulation (sod) and energy metabolism (gapdh) have been analyzed in three common shallow-water Mediterranean scleractinian, namely Astroides calycularis, Balanophyllia europaea and Leptopsammia pruvoti. The main aim was to assess the contribution of these cytoprotective mechanisms to the physiological plasticity of the species, that possess different growth modes (solitary vs colonial) and trophic strategies (zooxanthellate vs azooxanthellate). Using quantitative real-time PCR, expression profiles after an acute heat-shock exposure (2h at 32°C + 0-24 h post-stress recovery) were assessed, and a potential timeline for the events occurring in the investigated species was disclosed. The overall transcriptional response to heat stress aligns with relative differences in stress susceptibility of the species and suggests a contribution of trophic strategy in the degree of coral resilience to stress. Understanding the overall molecular processes is demanding for corals inhabiting the Mediterranean (a biodiversity “hot spot”), in light of projected scenarios of anthropogenic global change.

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SANTO, ANDREA. "Seed germination requirements and salt stress tolerance of coastal rare species in Sardinia." Doctoral thesis, Università degli Studi di Cagliari, 2013. http://hdl.handle.net/11584/266220.

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To survive to adverse factors that characterize coastal environments, plant species often require special physiological or metabolic adaptations to overcome environmental stresses. Stress may be physical (e.g. temperature) or chemical (e.g. salinity). Many communities comprise highly specialized species, which have comparatively restricted geographical distributions. The coastal species investigated in this Ph.D. program were chosen accordingly to their habitat: Phleum sardoum (Hackel) Hackel and Rouya polygama (Desf.) Coincy for sandy dunes; Brassica insularis Moris and Lavatera triloba L. ssp. pallescens (Moris) Nyman for coastal cliffs; Lavatera triloba L. ssp. triloba and Halopeplis amplexicaulis (Vahl) Ces., Pass. & Gibelli for ultra-saline environments. Moreover, seed germination ecology of L. agrigentina Tineo, a species growing in clayey-chalky plains of South Italy, was also investigated for a comparative study within the Lavatera genus. For all the studied species, light and temperature requirements for seed germination were evaluated; their germination responses to salt stress (NaCl) and their germination recovery. Interpopulation variability on germination patterns was also evaluated for R. polygama, B. insularis and L. triloba ssp. triloba. Salt spray tolerance on the vegetative growth and biomass production during the early seedling developmental stages was evaluated for B. insularis, L. triloba ssp. pallescens, L. triloba ssp. triloba and H. amplexicaulis. Light did not affect germination percentages in any of the studied species enabling seed germination also under soil surface and highlighting that seeds were not photo-inhibited for germination. Seed germination of P. sardoum and R. polygama, as well as that of L. agrigentina, L. triloba ssp. pallescens and L. triloba ssp. triloba, reflected the optimal range of temperatures of “typical” Mediterranean species, suggesting germination in autumn-winter, when water availability, soil moisture and rainfalls are high, and temperatures are not excessively prohibitive for germination and consequent seedlings establishment. B. insularis differed from other “typical” Mediterranean plants, for which germination at low temperatures is a widely extended trait, demonstrating that germination of this species may occur in a wide time window during the year. H. amplexicaulis seed germination was highly promoted by the daily fluctuation of temperatures, while germination at constant temperatures was sensibly lower. Salinity tests showed higher germination percentages in the non-saline conditions, with seed mortality increasing proportionally with NaCl concentrations and temperatures. Salt tolerance limits varied among species, from a minimum of 100 mM NaCl for P. sardoum to 600 mM for H. amplexicaulis and L. triloba ssp. pallescens, without a clear habitat related pattern. The species for which salt spray experiments were conducted showed different responses on seedling growth to salt aerosol tolerance, with these differences being related to the habitat of each species and their distance from the sea. Populations of B. insularis and L. triloba ssp. pallescens, growing in coastal cliffs highly influenced by wind and salt spray, showed the lowest seedling mortality. High interpopulation variability in salt spray tolerance was detected for B. insularis, between a coastal and an inland population, with the latter resulting not adapted to this abiotic environmental factor. Seedling survival of the two inland species (L. triloba ssp. triloba and H. amplexicaulis) was inversely proportional to the increase of nebulization frequency, demonstrating a low adaptation to salt spray, likely due to their distance from the sea coast and/or to interposed vegetation that may determine a lower impact of marine aerosol. The results of this study lead to a better knowledge on the autoecology of the investigated species and to their limits of tolerance to abiotic factors such as temperature, soil salinity and salt spray.

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PUMO, Dario. "ECOHYDROLOGICAL MODELLING IN MEDITERRANEAN AREAS AND WETLANDS." Doctoral thesis, Università degli Studi di Palermo, 2010. http://hdl.handle.net/10447/292397.

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La seguente dissertazione verte sul campo di ricerca noto come Ecoidrologia. Sebbene tale scienza, che studia le mutue interazioni fra ciclo idrologico e gli ecosistemi naturali, sia stata recentemente oggetto di svariati studi, alcuni dei suoi numerosi aspetti rimangono tuttavia ancora alquanto inesplorati. L’obiettivo principale della presente tesi è quello di rivisitare la letteratura scientifica esistente sull’argomento, cercando di adattare concetti e modelli sviluppati per certi ecosistemi anche alle peculiarità di altri ambienti meno studiati, come quelli aridi e semiaridi tipici della zona Mediterranea o le cosiddette “wetlands”, zone umide e paludose. In particolare, viene approfondito un approccio ecoidrologico allo studio di quegli ecosistemi controllati dalla risorsa idrica (water-controlled ecosystems) in aree Mediterranee ed a quegli ecosistemi controllati dalla falda acquifera (groundwater dependent ecosystems). Questi due tipi di ambiente sono profondamente diversi fra loro, ma è senz’altro la posizione della falda idrica a giocare un ruolo chiave. Se da un lato infatti, gli ecosistemi aridi e semiaridi sono generalmente caratterizzati da un acquifero cosi profondo da non esercitare alcuna influenza sul bilancio idrico del suolo, dall’altro lato, nel caso di “groundwater dependent ecosystems”, la posizione della falda idrica interagisce con la zona radicale della vegetazione, controllando i più importanti meccanismi di interazione fra processi idrologi ed ecologici. Nel campo delle Ecoidrologia, la letteratura scientifica esistente su ecosistemi aridi e semiaridi come savane o ambienti tropicali risulta essere piuttosto ampia, completa e consolidata. In tali ecosistemi, l’umidità del suolo rappresenta certamente l’anello di congiunzione fra le variazioni climatiche e le dinamiche pedologiche e vegetative. I più comuni modelli ecoidrologici relativi a tali ambienti hanno alla base un equazione stocastica differenziale che descrive il bilancio idrico del suolo, dove l’incognita, rappresentata dall’umidità del suolo, dipende sia dallo spazio che dal tempo. La maggior parte delle soluzioni a tale bilancio sono state ottenute in termini probabilistici è sotto l’ipotesi di stazionarietà. Tale ipotesi però, sebbene consenta la soluzione analitica del problema, semplifica considerevolmente l’analisi togliendo generalità da essa. L’ipotesi di stazionarietà risulta infatti perfettamente applicabile in aree climatiche aride e semiaride come quelle Africane o delle savane del Centro America, mentre sembra essere non più applicabile in quelle aree Mediterranee dove, notoriamente, la stagione umida precede la stagione vegetativa, ricaricando di acqua il suolo. L’acqua immagazzinata all’interno del terreno all’inizio della stagione vegetativa (nota come condizione iniziale di umidità del suolo) ha un ruolo chiave per la vegetazione, specialmente per quella avente un apparato radicale più profondo, garantendone la sopravvivenza anche in assenza di pioggia durante la stagione vegetativa o comunque mantenendo bassi i valori di stress idrico durante la prima fase della stagione stessa. Nella seguente tesi viene presentato un approccio numerico sviluppato durante il corso triennale di Dottorato presso l’Università degli Studi di Palermo. In particolare, viene proposto un modello ecoidrologico numerico non stazionario per la studio delle dinamiche di umidità del suolo e la conseguente risposta della vegetazione in termini di stress idrico. Tale modello è in grado di riprodurre la funzione densità di probabilità di umidità del suolo, ottenuta analiticamente in precedenti studi relativamente a regimi climatici differenti e sotto l’ipotesi di stazionarietà. Attraverso un prima applicazione di tale modello al bacino siciliano dell’Eleuterio al Lupo, viene mostrato come lo stesso modello sia in grado di computare i profili temporali di umidità del suolo e di stress idrico statico per la vegetazione anche in condizioni non stazionarie, tenendo quindi in considerazione gli effetti dovuti alla ricarica invernale di umidità all’interno del terreno. Una delle possibili applicazioni del modello è quella di studiare gli effetti di potenziali cambiamenti climatici sullo stress vegetativo di ecosistemi Mediterranei. Recenti studi hanno infatti dimostrato che l’aumento di CO2 sta gradualmente guidando il clima relativo alle aree Mediterranee verso importanti cambiamenti, principalmente rappresentati da un aumento delle temperature e una contemporanea riduzione delle piogge. Partendo da tale premessa, attraverso un seconda applicazione del modello al bacino dell’Eleuterio al Lupo, vengono analizzati i possibili effetti che diversi scenari futuri potrebbero avere sulla vegetazione in termini di stress idrico. Come precedentemente menzionato, tantissimi sono i lavori che studiano le interazioni fra clima, suolo e vegetazione in ecosistemi aridi e semiaridi controllati dalla risorsa idrica. E svariati approcci analitici ci hanno consentito di ottenere un descrizione probabilistica delle dinamiche di umidità del suolo in tali ecosistemi, partendo dalla conoscenza delle precipitazioni e delle caratteristiche del suolo e della vegetazione. Recentemente grandissima attenzione è stata anche focalizzata sull’importanza di ambienti quali le zone riapariali, le paludi e le zone umide in generale, considerate come un serbatoio di biodiversità fondamentale per la sostenibilità ambientale. In tali aree la posizione della falda idrica gioca un ruolo fondamentale nei maggiori processi eco idrologici e proprio per questo motivo, tali ecosistemi vengono anche definiti groundwater dependent ecosystems. In tali tipi di ambienti, solo pochi lavori in letteratura hanno proposto un approccio probabilistico per lo studio le dinamiche di umidità del suolo e delle falda idrica, analogo al caso degli ecosistemi controllati dalla risorsa idrica. Recentemente sono stati sviluppati due modelli ecoidrologici analitici per groundwater dependent ecosystems, il primo in grado di studiare la posizione della falda idrica e il secondo per lo studio delle dinamiche di umidità del suolo. Nella presente tesi, dopo aver presentato i due modelli, vengono anche mostrati i risultati di una validazione del primo modello, ottenuta mediante una sua applicazione a tre siti all’interno delle Everglades della Florida (USA), aventi dati di campo disponibili. The present dissertation focuses on the field of research known as ecohydrology. Although this science, studying the mutual interactions between hydrological cycle and natural ecosystems, has been deeply investigated in recent past, some of its numerous aspects are still relatively unexplored. The main purpose is to investigate the existing scientific literature in order to adapt concepts and models previously developed for some specific ecosystems to the peculiarities of other less explored environments such as those semi-arid within the Mediterranean zone and the wetlands. In particular this study explores an ecohydrological approach to the analysis of water-controlled ecosystems in Mediterranean areas and groundwater dependent ecosystems. Although both are strongly reliant on water availability, these two kinds of environments are deeply different with each other. The most important difference is certainly played by the position of the water table. While on the one hand arid and semiarid ecosystems are usually characterized by a deep aquifer that does not exert any influence on soil water balance, on the other hand, in the case of groundwater dependent ecosystem, the water table position interacts directly with the root zone leading to important feedbacks between hydrological and ecological processes. The existing ecohydrological literature on arid and semiarid ecosystems such as savannas, steppes, deserts and prairies is rather wide, complete and consolidated. In such ecosystems, the soil moisture plays a fundamental role in the mutual links between climatic variations and the pedological and vegetational dynamics. The most common ecohydrological models start from a stochastic differential equation describing the soil water balance, where the unknown quantity, the soil moisture, depends both on spaces and time. Most of the solutions existing in literature are obtained in a probabilistic framework and under steady-state condition; even if this last condition allows the analytical handling of the problem, it has considerably simplified the same problem by subtracting generalities from it. The steady-state hypothesis, appears perfectly applicable in arid and semiarid climatic areas like those of African’s or middle American’s savannas, but it seems to be no more valid in areas with Mediterranean climate, where, notoriously, the wet season foregoes the growing season, recharging water into the soil. This soil moisture stored at the beginning of the growing season has a great importance, especially for deep-rooted vegetation, by enabling survival in absence of rainfalls during the growing season and, however, keeping the water stress low during the first period of the same season. In this thesis, a numerical approach, developed during the triennial graduate school at the University of Palermo, is presented. In particular a non steady numerical ecohydrological model is here proposed to evaluate the soil moisture dynamics and the consequent vegetation response in terms of water stress in Mediterranean areas. Such model is able to reproduce soil moisture probability density function, obtained analytically in previous studies for different climates in steady-state conditions. A first application of this model to the Sicilian river basin of Eleuterio at Lupo (Italy) shows how the model allows to compute the soil moisture time-profile and the vegetation static water stress time-profile in non-steady conditions, resulting able to capture the effects of winter recharge on the soil moisture. One of the possible applications of such model is to investigate the effects of potential climatic changes on vegetational stress in Mediterranean ecosystems. Many recent studies have demonstrated that CO2 increase is driving the climate in Mediterranean areas towards important changes, mainly represented by a temperatures increase and a contemporaneous rainfall reduction. Starting from this premise, the potential responses of vegetation, in terms of plants water stress, to different future scenarios are here investigated, throughout a second application of the model to the same river basin. In recent years great attention has been paid to environments such as riparian zones, peatlands and unsubmerged wetlands, which are considered as fundamental “tanks” of biodiversity and where the water table plays a key role in major ecohydrological processes. Wetlands are groundwater dependent ecosystems, which require access to the water table to maintain their health and vigor. A new fascinating challenge for the scientific community is that to investigate such environments by an ecohydrological approach. The study of the dynamics of interactions between climate, soil and vegetation in groundwater dependent ecosystems requires to couple the water table dynamics with the dynamics of soil moisture in the unsaturated zone. Only few recent frameworks have investigated a probabilistic approach also for the description of soil moisture and water table dynamics in the case of groundwater based ecosystems. In particular two models, the first for the analytical estimation of the water table position and the second for the analysis of the soil moisture dynamics, have been recently developed. Here, it is also presented a validation of the first model, which is the result of its application to three different sites within the Florida Everglades (USA).

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DE, CICCO MARCO. "Effects of a small headwater dam on macroinvertebrate communities and environmental variables in a Mediterranean stream." Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2008. http://hdl.handle.net/2108/449.

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Macroinvertebrate communities were investigated over 1-yr period at three reference sites and at six impacted sites located upstream and downstream of a small dam located in the Simbrivio Stream (Tiber basin, Central Italy). Data on physicochemical, hydro-morphological and trophic variables were collected to assess possible dam effects on taxonomic composition, density, diversity and trophic structure of macroinvertebrate communities. Major changes in environmental variables occurred within the first three sites below the dam (distance<1km): alteration of flow regime (characterized by a constant, residual flow and, in rainy period, by short-term fluctuations), increase of epilithic biomass and, during spring period, decrease of the coarse and fine particulate organic matter associated with benthic samples. Water temperature, conductivity, pH, dissolved oxygen and nutrient concentrations (ammonium and soluble reactive phosphorus) were not affected by river regulation. The effect of the Simbrivio Dam on assemblages of macroinvertebrate communities was noticeable in the spring sampling, where the qualitative composition of benthic fauna below the dam differed from that above it. In this period, the dam produced an alteration of the taxonomic composition and a reduction of taxa richness of downstream sites, particularly in relation to stoneflies, caddisflies and mayflies (EPT taxa). Many taxa of stream insects disappeared at short or long-distance from the dam. Nevertheless, a few of these taxa (as Epeorus assimilis, Isoperla saccai, Rhithrogena gr. hybrida) were collected below the dam in the autumn sampling. Thus, the prevailing conditions of constant flow might favour the presence of these taxa but the sudden rises in river flow due to short-term fluctuations (in winter and spring) had a harmful interference on life cycles of some specific taxa. In this period, macroinvertebrate communities of boulders were the most affected by river regulation. On the contrary, in autumn, the results showed an increase of total and EPT taxa of downstream communities. The effect of the Simbrivio Dam on trophic structure of macroinvertebrate communities was evident on scrapers and collector filterers in spring period, and on shredders in autumn period. The analysis of environmental variables patterns along the watercourse suggested that the principal factors affecting the macroinvertebrate communities at downstream sites were alteration of hydrological conditions, epilithic development and heterogeneity and stability of substrata. In the present study, total densities and diversity indices are probably not the most appropriate macroinvertebrate community metrics for assessing the effects of stream regulation caused by a small dam. Taxonomic composition gives a better interpretation of the alteration of the biota. Finally, Plecoptera and Ephemeroptera Heptageniidae seem to be the most affected taxa to river regulation

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Gaspar, Margarida Veríssimo. "Implicações da sazonalidade na avaliação do estado ecológico em rios de tipo mediterrâneo: será a amostragem adequada?" Master's thesis, Universidade de Évora, 2013. http://hdl.handle.net/10174/16095.

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Os rios de tipo mediterrânico estão sujeitos a grandes variações sazonais e inter-anuais de caudal o que, associado à degradação antrópica, vai implicar alterações nos agrupamentos biológicos ao longo do tempo. Os protocolos de monitorização do estado ecológico estabeleceram amostragens de primavera, e os índices foram desenvolvidos nesse sentido. Este trabalho teve como objectivo principal comparar a resposta de índices piscícolas e de macroinvertebrados na primavera e no outono. Os resultados mostram que, no geral, os valores dos índices no outono não são inferiores aos de primavera, como se poderia esperar, concluindo-se que é viável monitorizar com amostragens de outono. Complementarmente, comparou-se a responsividade dos diversos índices à degradação. Nos macroinvertebrados, IBMWP e IPtI foram os mais responsivos, em oposição a IM9, e na ictiofauna foram F-IBIP e NMR mais responsivos em oposição a IBI; ABSTRACT: Mediterranean type rivers are subject to large seasonal and inter-annual flow variations. This natural variability, with the different anthropogenic pressures, causes changes through time on the biological assemblages. The monitoring protocols for the ecological assessment refer sampling should take place in spring. The main goal of this study was to compare the response of invertebrate and fish indexes in spring and in autumn. Results show that, in general, the indexes values for autumn are not lower than the spring ones, as could be expected, which means that autumn sampling may be considered as an alternative to the usual spring sampling. The indexes response to human pressures were also compared. For macroinvertebrates, IBMWP and IPtI showed the best performances and IM9, the worse; for fishfauna, F-IBIP and NMR responded best to pressures and IBI had the worse performance.

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Sperlich, Dominik. "Mediterranean forests in a changing environment - Impacts of drought and temperature stress on tree physiology." Doctoral thesis, Universitat de Barcelona, 2015. http://hdl.handle.net/10803/327595.

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The Mediterranean Basin is a climate-change hotspot of the world. Predicted reductions in annual precipitation, increases in mean temperature, and increases in the variability and occurrence of extreme droughts and heat waves are likely to affect species abundance and distribution. The existence of sympatric plants with different morphological and phenological strategies raises the question how they will respond to novel climate conditions. There is a strong need to improve the mechanistic understanding of key foliar ecophysiological parameters in response to abiotic stressors on a small scale if we are to predict the carbon budget of plant ecosystems in larger scales. We first reviewed contrasting growth responses to temperature of angio- and gymnosperms in the Iberian Peninsula. Secondly, we studied the seasonal acclimation of different foliar ecophysiological traits in two leaf positions of four Mediterranean tree species in extensive field experiments. We aimed to shed light on the mechanistic understanding of the foliar respiratory and photosynthetic responses to abiotic stress such as drought and temperature. We found contrasting demographic responses in Mediterranean conifer and angiosperm trees. Widespread forest successional advance of angiosperms and negative growth responses of gymnosperms to temperature are currently occurring in the Iberian Peninsula. Trait-based differences in these two groups contribute to explain their different responses to temperature and their different role during successional processes. The acclimation behaviour of photosynthetic and morphological traits to seasonal variable growth conditions was strongly pronounced in all tree species. Photosynthetic machineries were resilient to moderate drought, whereas severe drought induced acclimation of morphological traits, photosynthetic downregulation and leaf abscission. The lack of replenishment of soil-water reserves during the early growing season critically enforced the summer drought. We also observed a notable seasonal acclimation of the thermal optima and of the curvature of temperature responses of photosynthetic assimilation. The photosynthetic system was better acclimated to lower temperatures in winter and to heat stress in the drier and hotter year. Mild winter temperatures provided a period of growth and recovery that resulted in biochemical recovery, new shoot growth, and moderate transpiration across all evergreen species. High radiation and sudden low temperatures had a combinatory negative effect on the photosynthetic apparatus leading to photoinhibitory stress -especially in sunlit leaves. Species-specific acclimation partly offset these overall trends in responses to drought and temperature stress. Quercus ilex L. and to a lesser extent Q. pubescens Wild. showed the highest plasticity in photosynthetic traits whereas Pinus halepensis Mill. was most tolerant across the seasons with the most stable temperature response pattern. Arbutus. unedo L. was the most vulnerable to drought and photoinhibitory stress in winter. A. unedo and Q. pubescens had a less sclerophyllic leaf habit and invested the least in acclimation of the morphological structure being most vulnerable to drought-induced leaf abscission. Shaded leaves showed generally a lower photosynthetic potential, but cushioned negative impacts under stress periods. A long-term rainfall-exclusion experiment in a Q. ilex forest increased the foliar carbon-use efficiency and the plasticity of foliar respiratory and photosynthetic traits, but did not affect the biochemical photosynthetic potential. A favourable growth period was thus exploited more efficiently. Overall, our results indicate that Mediterranean climax-species exhibit a strong acclimatory capacity to warmer and drier conditions, but can be sensitive to extreme drought and extreme temperature stress. The performance of the plants during winter might give important insights in the dynamics of Mediterranean forest communities under novel environmental conditions. Leaf position is an indispensable factor when estimating the canopy carbon balance. Angiosperms and gymnosperms had fundamental different photosynthetic strategies of stress-avoidance versus stress-tolerance, respectively. El cambio climático aumentará la sequía en la Cuenca Mediterránea y posiblemente afectará a la abundancia y la distribución de especies. Revisamos las respuestas contrastadas del crecimiento a la temperatura de angio- y gimnospermas en la Península Ibérica. Estudiamos la variación de los efectos del estrés térmico y por sequía en rasgos morfológicos, fotosintéticos y de la respiración foliar según la especie y la posición en el dosel. Además, evaluamos el efecto de una sequía crónica sobre la respiración foliar y la fotosíntesis de Quercus ilex L. La maquinaria fotosintética se mostró resiliente frente a la sequía moderada, mientras que la sequía extrema, agravada por las bajas reservas de agua en el suelo, indujo la aclimatación de la morfología foliar, la inhibición de la bioquímica fotosintética y la abscisión foliar. El sistema fotosintético se aclimató mejor a las temperaturas bajas que al estrés por calor. Las temperaturas suaves en invierno derivaron en la recuperación bioquímica, un nuevo crecimiento de los brotes y una transpiración moderada. La elevada radiación y el frío repentino mostraron un efecto combinado negativo, causando estrés fotoinhibitorio. El estrés térmico y por sequía fue más pronunciado en hojas de sol y aminorado en hojas de sombra. Q.ilex y, en menor grado, Q. pubescens Wild. mostraron la plasticidad más elevada de los rasgos fotosintéticos, mientras que Pinus halepensis Mill. fue más tolerante, mostrando la respuesta más estable a la temperatura. Arbutus unedo L. fue la especie más vulnerable a la sequía y al estrés fotoinhibitorio. En respuesta a la sequía crónica, Q. ilex incrementó la eficiencia en el uso del carbono y la plasticidad de los atributos fotosintéticos y de respiración foliar, pero no afectó al potencial fotosintético. En resumen, las especies climácicas mediterráneas se aclimatan frente a condiciones más cálidas y secas, pero pueden ser sensibles ante sequías extremas. El funcionamiento durante el invierno es vital para entender la dinámica de los bosques mediterráneos. La posición de las hojas en la copa es indispensable para estimar el balance de carbono del dosel. Angiospermas y gimnospermas presentan estrategias fotosintéticas contrastadas, de evitación y tolerancia del estrés, respectivamente.

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Pérez-Llorca, Marina. "Structural and physiological mechanisms underlying abiotic stress tolerance in the Mediterranean shrub Cistus albudus L." Doctoral thesis, Universitat de Barcelona, 2021. http://hdl.handle.net/10803/672951.

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Mediterranean species have to be in constant acclimation to seasonal environmental changes, including variations in water availability, air temperature and solar radiation. Due to global warming, these environmental changes are predicted to increase in frequency and intensity. Shrubs have a crucial role in plant communities such as avoiding soil erosion and, therefore, the study of shrub responses to abiotic stresses is essential to predict future changes in populations. Here, we evaluated the performance of the Mediterranean shrub, Cistus albidus, under several abiotic stresses in natural and controlled conditions. It was found that C. albidus plants have to face several combinations of abiotic stressors, with drought and cold being the main environmental cues that threaten their performance during winter. As a first line of defence, C. albidus diurnally changed the angle of their most apical leaves together with a decussate leaf disposition to avoid photoinhibition. Structural mechanisms were not always effective for the whole plant, and carotenoids had a primordial role during the day, dissipating excess energy as a second line of defence. They also had an important function under sustained winter stress, but α-tocopherol was the crucial antioxidant responding to stress, as a third line of defence. Jasmonates seemed to be involved in many abiotic stress responses, including cold stress and drought. High jasmonates contents, especially those of 12-oxo-phytodienoic acid, jasmonic acid and jasmonoyl-isoleucine, were found in natural conditions during a particularly cold day and after a winter drought event in C. albidus seedlings. Furthermore, it is shown that α-tocopherol and jasmonates have an important role in drought tolerance and survival of seedlings in natural field conditions. Even though seedlings have evolved numerous mechanisms to tolerate stress, there was a 30% decrease in survival after summer drought. It is concluded, given the variability in stress responses and the number of mechanisms to withstand abiotic stress, that C. albidus is a highly tolerant and resilient plant to abiotic stress. However, there are still tipping points that could become more frequent in the wake of global change that could cause shifts in C. albidus populations.

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Scucchia, Federica. "Transcriptional profiles inferring thermal stress responses of the coral Oculina patagonica from the Eastern Mediterranean Sea." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/17967/.

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During the past several decades, corals worldwide have been dealing with a considerable increase in water temperature due to climate change, which is predicted to increase the frequency of coral bleaching and mass mortality events. Nevertheless, corals show differences in stress susceptibility and they are not all affected evenly. The symbiotic coral Oculina patagonica from the Eastern Mediterranean Sea can thrive in relatively unstable environments and is considered a stress-tolerant species. In this study, baseline expression and temporal dynamics of induction of a 70-kDa heat shock protein (HSP70) after an acute heat stress were analyzed in O. patagonica to investigate the influence of its peculiar physiological traits on stress responsiveness. Furthermore, data collected were further discussed within a comparative analysis with similar findings reported in 5 temperate corals of the Mediterranean Sea (Franzellitti et al., 2018). Results show that O. patagonica hsp70 transcriptional response aligns with the formerly observed high resistance for elevated sea water temperatures of this species. The multispecies comparison shows that hsp70 expression varies in accordance with the stress sensitivity of coral populations inhabiting different thermal environments and possessing different trophic strategies and morphologies. This study also reports an analysis of the post heat-stress transcriptional regulation of transcripts related to energy metabolism (gadph), redox regulation (sod), and DNA damage (bcl-2 and bax), disclosing the time line of the events occurring in O. patagonica in response to an acute heat stress, which aligns with its quick recovery from bleaching. These molecular processes analysis is particularly demanding for corals inhabiting the Mediterranean Sea, in light of projected scenarios of anthropogenic global change.

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Artigas, Alejo Joan. "The role of fungi and bacteria on the organic matter decomposition process in streams: interaction and relevance in biofilms." Doctoral thesis, Universitat de Girona, 2008. http://hdl.handle.net/10803/7874.

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L'objectiu d'aquest estudi és el d'investigar sobre l'ús de matèria orgànica per part dels fongs i bacteris que colonitzen diferents substrats bentònics en rius Mediterranis i analitzar l'efecte dels factors ambientals i antròpics sobre l'estabilitat estructural i funcional de les comunitats del biofilm. La metodologia emprada en aquest estudi consisteix en: i) anàlisi de la biomassa bacteriana i fúngica, ii) anàlisi de la composició de les comunitats bentòniques (identificació d'hifomicets aquàtics i anàlisi del 16S rDNA bacterià), i iii) anàlisi de l'activitat enzimàtica extracel·lular relacionada amb el reciclatge de matèria orgànica en rius. This study aimed to investigate on the use of organic matter by fungi and bacteria inhabiting different benthic substrata and to analyze the effect of environmental and anthropogenic perturbations on the structural and functional stability of biofilms. The following methodologies has been used in this study: i) analysis of fungal and bacterial biomass, ii) analysis of benthic community composition (identification of hyphomycete taxa, analysis of the bacterial 16S rDNA), and iii) analysis of extracellular enzyme activities involved in organic matter recycling in rivers.

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Jackson, Breeanne Kathleen. "The role of wildfire in shaping the structure and function of California `Mediterranean’ stream-riparian ecosystems in Yosemite National Park." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1431014316.

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CESARETTI, SABRINA. "Plant co-existence mechanisms related to stress and disturbance intensities in sub-Mediterranean and sub-desertic grassland systems." Doctoral thesis, Università degli Studi di Camerino, 2012. http://hdl.handle.net/11581/401800.

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Plant species co-existence may depend upon a complex chain of events involving competitive ability, complementarity and facilitation between plants and numerous interactions with herbivores, pathogens, soil features, fauna and micro-organisms. The co-existence of species in herbaceous vegetation is possible by the presence of factors that limit the expression of the dominance of plants. This limitation may operate through stress or disturbance or by a combination of the two, and its effect is usually to debilitate the potential dominants and to allow plants of smaller stature to regenerate and to co-exist with them. Species co-existence can reflect niche partitioning at several spatial and temporal scales. The functional strategies avoiding the temporal and/or spatial overlapping of the neighbouring individuals are key factors in the niche partitioning inside the plant community, so that species do not exclude each other by competition. Stress and disturbance are the two external factors affecting the vegetation. Their effects on the system change according their intensity. Stress includes factors which restrict the photosynthetic activity. In fact, plant biomass production in vegetation is subjected to a variety of environmental constraints, the most frequent of which are related to shortages and excesses in the supply of solar energy, water, and mineral nutrients. Disturbance includes mechanisms which limit the plant biomass by causing its partial or total destruction (grazing, mowing, forest cutting, soil erosion, and fire). Vegetation composition and species distribution may be influenced by negative processes (competition) and positive interactions (facilitation). Competition shows a maximal intensity in habitats with high productivity and low disturbance, while this phenomenon disappears under conditions of low productivity or intense disturbance. In order to obtain a more complete assessment of the role of these factors upon species density it is necessary to consider the rather different circumstances which arise when the intensities of stress and/or disturbance become severe. In harsh habitats plants are subjected to extreme stress or disturbance conditions, thus seedling establishment is promoted under the canopies of established vegetation. In this positive interaction, known as facilitation, some plants benefit from closely associated neighbours. The intensities of stress and/or disturbance experienced by herbaceous vegetation are sufficient, not only to eliminate potential dominants but also to produce local environments which are inhospitable to all, except a few specialised plants. Facilitation occurs widely but is more frequently documented in unproductive habitats and dominates under harsh conditions. Stress and disturbance involve functional responses by plants; thus, the analysis of plant functional traits (biological characteristics of plants responding to the dominant processes in an ecosystem) is a useful tool for the understanding of plant community assemblage. Grazing is a major disturbance which often causes extensive changes in plant richness and composition. However, pasture plants do not undergo herbivory passively, but react to defend themselves against grazers by means avoidance and tolerance strategies that enable them to survive and grow in grazed systems. Grazing avoidance involves mechanisms that reduce the probability and severity of grazing (mechanical and chemical defence or escape strategy), while grazing tolerance consists of mechanisms that promote growth following defoliation. The research aim was to assess how different types and intensity of disturbance affect species and functional composition of sub-Mediterranean and sub-desertic grassland systems, also in relation with environmental stress. Consequently, the specific research goals were to: i) identify changes in species and functional trait composition and in diversity of plant communities, under different disturbance types (grazing vs. mowing; mown vs. unmown meadows; grazed vs. ungrazed pastures; sheep grazing vs. horse grazing); ii) identify coenological and functional responses of grassland to intensity of stress and intensity and timing of disturbance, by analysing the plant functional traits, that are expression of competitive ability, facilitation, co-existence, avoidance and tolerance strategies; iii) identify plant-plant spatial interactions, i.e. whether species have species-specific spatial associations, especially in harsh environments, and understand how disturbance intensity affect species co-occurrence. Two study areas were considered: sub-Mediterranean grasslands of Umbria-Marches Apennine (central Italy) and the sub-desertic rangelands of southern Peruvian Andes (Peru). In the studied sub-Mediterranean grasslands the competition for light and soil resources may be extremely intense among species. In fact, competition plays a key role, especially in dense and more productive grasslands, where the co-existence of plants is mainly linked to the competitive exclusion. For this reason, in these plant communities the species co-existence is driven by a specific pattern of functional plant traits that ensures foliage expansion affording a competitive advantage. Furthermore, clonal growth forms and vegetative propagation modes that imply horizontal space occupation, can be interpreted as a strategy aimed at maximizing the species competitive ability when there is higher exploitation of soil resources, allowing individuals to explore the neighbouring areas and find unexploited soil niches. This helps to avoid competition for soil resources with the dominant species. Accordingly, the plant functional composition also affects the competitive ability in relation to the stress and the disturbance intensity. In terms of biodiversity conservation, the research outputs represent an advance in the understanding of the ecological processes involved at plant community level, as well as at landscape scale. Some plant traits may reflect selection by herbivores, while others are likely to be by-products of selection for other ecological functions. Moreover, several plant traits may have a dual role. The study findings allow to highlight a general scheme, in which the stress intensity filters the pool of traits at landscape scale, while the disturbance intensity leads to the distribution, occurrence and abundance of single traits at plant community level. Stress intensity (drought stress) selects the trait composition of the plant community at a landscape scale. Thus, traits and associated plant species are distributed at landscape scale depending on stress intensity. In xeric grassland, stress tolerance and avoidance strategies by hairs and leaf texture, determining low evapotranspiration and low palatability, are widespread. Therophyte and chamaephyte life forms are fostered. In semimesic condition either avoidance mechanisms (rosette form, chemical substances, spines and prostrate form) or tolerance strategies (re-growth capacity) occur, as well as late flowering and tall species (upright forbs, tall tussock grasses). More productive environments develop numerous functional types and a higher floristic richness. Disturbance intensity (number of herbivores), type (mowing or grazing, and the different livestock type) and timing act as driving forces in promoting or suppressing the plant functional traits expression. The pool of traits is filtered in different ways by the system. High intensity of disturbance favours avoidance strategies (i.e. prostrate form, rosette forbs, hairs) and vegetative reproduction (clonal ability). The intermediate disturbance condition leads to the largest pool of traits that allows maximum floristic richness. The co-existence of species is promoted by the co-existence of avoidance and tolerance strategies, due to the possibility to use the maximum number of spatial (micro-scale) and temporal niches (change in sward structure during the growing season). In low intensity of disturbance and abandonment conditions, tolerance strategies and dominant species are promoted; on the contrary, the low statured (rosette and prostrate form), accidental and subordinate species are disadvantaged. Large herbivores like horses cause the increase of short grasses, sedges, rosette forbs and annuals (growth forms with poor root systems). These plants do not ensure the maintenance of soil on steep slopes. Upright forbs, dominant unpalatable tall grasses (Brachypodium rupestre) and chamaephyte species are promoted by selective defoliation of small herbivores like sheep. Facilitative interactions between palatable and unpalatable species were observed. Grazing in springtime negatively affects the early spring flowering species of mid/tall dimensions and relevant species such as orchids. This is an issue for biodiversity conservation. The research findings highlight the strong importance of plantâ€“plant spatial interactions in the Peruvian dry Puna. In this harsh environment many species need some kind of facilitative interaction with nurses (mainly with tall grasses, shrubs or cushion plants). Tall grasses (mainly Festuca orthophylla) are the most important nurse species because they have the highest number of spatially associated plants. Thus, the management of this species should be viewed as a key factor for dry Puna biodiversity conservation. In fact, as camelids prefer the fresh, regrown leaves of F. orthophylla that resprout after burning throughout the Peruvian dry Puna, there is the widespread practice of burning these plant communities to renew forage for livestock. Subsequent to burning, shelter and regenerative niches are probably few and small for some years. Because of this, species with strong spatial relationship with F. orthophylla could be threatened with local extinction, especially in conditions of overgrazing. The effects of combined overgrazing and fire lead to the decrease of tall species F. orthophylla and to an increase of the dwarf and spiny shrub Tetraglochin cristatum. The reduction of nurse cover value leads to the decrease of facilitative interactions and consequently to a reduction of species richness. Thus, inappropriate land use practices (e.g. excessive grazing and uncontrolled fire) are the fundamental causes of land degradation. The abundance of tall grasses and shrubs counters soil erosion by wind, and reduction of their cover value could lead to increased soil loss. This could contribute to desertification more than climatic change, or contribute to a cumulative process that amplifies the impact of climatic change. Key words: Avoidance and tolerance strategies, Competition, Facilitation, Plant functional traits, Plant-plant spatial interactions.

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BIANCHI, Elisabetta. "Seirophora villosa (Ach.) Frödén: a multidisciplinary investigation on morphology, ecophysiology and ecology." Doctoral thesis, Università degli studi di Ferrara, 2019. http://hdl.handle.net/11392/2487955.

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Questo progetto mira a studiare l’ecologia e la fisiologia di Seirophora villosa (Ach.) Frödén, specie epifita ritenuta in via di regressione a causa di una sempre più avanzata frammentazione del suo habitat preferenziale, il ginepreto costiero, habitat prioritario secondo la Direttiva 92/43 CEE (2250* “Dune costiere con Juniperus spp.”). La degradazione e la perdita dell’habitat in effetti sono ritenute le principali cause del declino delle popolazioni di S. villosa e recenti studi hanno evidenziato una correlazione positiva fra superficie locale dell’habitat e abbondanza di S. villosa. Tuttavia è stato dimostrato che, anche in situazioni ottimali, S. villosa non occupa tutto l’areale disponibile suggerendo una possibile implicazione di fattori ecologico/biologici limitanti la sua dispersione. Da queste considerazioni nasce questa ricerca che si propone di indagare sia a livello di popolazione che di individuo le caratteristiche che determinano la distribuzione di questa specie. Per raggiungere questi obiettivi abbiamo proceduto sia con esperimenti in campo che in laboratorio. In campo sono state valutate le relazioni che intercorrono fra le variabili strutturali del ginepreto e la diversità funzionale e specifica delle comunità licheniche epifite che lo ospitano e in particolare la relazione fra struttura dell’habitat e presenza di S. villosa. In laboratorio, sono stati indagati gli effetti delle principali variabili ecologiche sulla eco-fisiologia della specie al fine di caratterizzarne la nicchia ecologica. Abbiamo valutato le risposte fisiologiche della specie a cambiamenti di disponibilità della risorsa idrica e luminosa, in relazione alla dimensione dei talli. Inoltre, abbiamo indagato su di un carattere morfologico peculiare di questa specie, la pelosità del tallo, ipotizzando che questo carattere ricopra un ruolo primario nelle performance eco-fisiologiche della specie. Per indagare su questo aspetto abbiamo investigato eventuali meccanismi biochimici e fisiologici che la specie mette in atto per rispondere ed adattarsi alla presenza/assenza del pelo in superficie durante un ciclo di disidratazione e in presenza di stress salino. I risultati ottenuti dagli esperimenti a livello di popolazione mostrano che effettivamente un ginepreto continuo e strutturato porta ad una varietà e stabilità di microhabitat che supporta una forte differenziazione floristica e funzionale della comunità lichenica che lo ospita. Per quanto riguarda S.villosa, i nostri risultati confermano gli studi pregressi, evidenziando che le pratiche conservazionistiche per questa specie devono essere estese ad una scala ridotta, a livello di albero. I risultati di laboratorio mostrano che le dimensioni dei talli influiscono sulla capacità di ritenzione idrica dei questa specie; i campioni di S.villosa sono suscettibili ad una forte radiazione luminosa in particolare se questa è protratta nel tempo, in particolare i talli più piccoli che una volta fotoinibiti manifestano un’abilità di recupero piuttosto ridotta. Inoltre, i risultati confermano le nostre ipotesi a presenza dei peli sul tallo di S.villosa è risultato essere un tratto morfologico strategico per le performances di questa specie. La presenza del pelo offre un meccanismo passivo ma selettivo dell’acqua, regolandone l’assorbimento e la repulsione. Allo stesso tempo, aziona un meccanismo di resistenza passivo, di elusione dello stress, permettendo di tollerare la presenza di sale, in quanto ne impedisce l’entrata all’interno del tallo lichenico. Da un punto di vista pratico la conservazione della specie dovrebbe essere attuata garantendo le condizioni ideali a tutti gli stadi di crescita (ad esempio proteggere i propaguli dalla fotoinibizione). In caso di necessità di intervento valutare su scala locale la dinamica di popolazione e utilizzare questo dato per selezionare le aree e gli arbusti sui quali effettuare gli interventi. Light regime, water availability and high salt concentrations are generally the main ecological factors modified by habitat fragmentation that could be detrimental to the survival and establishment of poikilohydric organisms such as lichens, causing rapid dehydration, ionic imbalances and the inhibition of photosynthesis. In the Mediterranean basin, coastal juniper habitats, priority habitat for nature conservation (Natura 2000 habitat code 2250), are known to host numerous epiphytic lichens, that living near the seashore need a morphological and chemical organization to adapt or acclimate to extremely variable disturbances. Among them, the macrolichen Seirophora villosa, which consists in a fruticose habitus characterized by the presence of compressed canaliculated laciniae covered by thin hairiness and the absence of secondary surface metabolites. Recently studies, has demonstrated the dependence of S. villosa on undisturbed Juniperus stands suggesting a significant effect of disturbance on the presence of this lichen species. Moreover, it has been demonstrated that S. villosa is only occupying a small part of its colonizable niche because of a very limited propagation ability. Since the presence and abundance of S.villosa are positive indicators of the conservation status of coastal nurseries, our study aimed to evaluate the effects of the main ecological variables on the eco-physiology of this species. Our first aim was to investigate whether the habitat structure affects the functional diversity and species richness of lichen communities along a coastal dune system and how affects the presence of S. villosa. Our second aim was to investigate how light regime and water availability affect individual specimens of S. villosa, by studying the relationship between photosynthetic activity and water content to thallus area in different sized. Furthermore, we investigated the role of the thin hairiness on thallus surface characterizing S. villosa to withstand the effects of seawater by continuous exposure to marine aerosol. Our results showed that epiphytic lichens richness and habitat width used as proxy of habitat integrity. Juniperus stands with higher individuals and cover continuity, probably ensuring a major stability of microclimatic factors, supported richer and functionally more differentiated epiphytic lichen communities. In contrast, the presence of S. villosa resulted not directly related to the habitat structure, suggesting a major role of dispersal and establishment capability therefore suggesting a management tailored at the tree-level aimed to the conservation of mature (apotheciate) specimens. However, ongoing research indicate a possible role of microhabitat structure on the abundance of this species. The experiments carried out showed that the size of the thalli influence the water retention capacity of S.villosa species, and consequently influence responses to strong exposure to light. Our outcomes showed that S. villosa are susceptible to sudden increases in light exposure, especially in the case of small specimens, which after photoinhibition exhibited a reduced ability to recover. Moreover, our work evidenced for the first time the relevance of hair as a strategic morphological trait in lichens to face extreme environments. Our results suggest that hair could offer a passive, but selective, water control. Furthermore, hair could repel the salt dissolved in water, by activating a passive resistance mechanism, a real avoidance of stress, which by not allowing salt to enter, allows the thallus to tolerate the presence of salt. In conclusion, from a conservation point it would be necessary to preserve all the growth stages of the population, providing a suitable habitat for the larger thalli that have the role of propagate the species and for the smaller ones giving them the opportunity to colonize and establish in fragment habitat without being photohinbited.

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Casas, Ruiz Joan Pere. "Controls on the dynamics of riverine dissolved organic matter: insights from a Mediterranean river network." Doctoral thesis, Universitat de Girona, 2017. http://hdl.handle.net/10803/404280.

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In river networks, dissolved organic matter (DOM) constitutes the major pool of organic carbon, and plays a key role as energy source and modulator of toxic substances availability. In this thesis, Joan P. Casas-Ruiz and collaborators provide new insights into the controls on DOM processing, and into how in-stream reactions and changing DOM sources modulate DOM dynamics in river networks. To attain this, the quantity and composition of DOM were evaluated across a river network throughout a full hydrological year. The results compiled in this thesis pose water residence time as the main regulator of DOM processing, while DOM properties as well as nutrient availability determine the net balance of in-stream degradation and production of DOM. A network-scale analysis identifies a pattern of DOM concentration and chemical diversity with maxima in medium-sized rivers, and the same pattern emerges upon analysis of a global data set. On the basis of these results, this thesis proposes a conceptual framework to comprehend and predict the spatiotemporal dynamics of riverine DOM La matèria orgànica dissolta (DOM) constitueix la major reserva de carboni orgànic en els sistemes fluvials, on també hi juga un paper clau com a font d'energia i modulador de la disponibilitat de substàncies tòxiques. En aquesta tesi, Joan P. Cases-Ruiz i col•laboradors pretenen identificar els controls de processament DOM, i entendre com la combinació de reaccions in situ i canvis en les fonts de DOM modulen les dinàmiques de la DOM fluvial. Per tal d'assolir-ho, es van evaluar la quantitat i composició de la DOM en una xarxa fluvial al llarg d'un any hidrològic complet. Els resultats recopilats en aquesta tesi assenyalen el temps de residència de l'aigua com el principal regulador de processament de la DOM, mentre que les propietats intrínsiques de la DOM, així com la disponibilitat de nutrients determinen el balanç net de degradació i producció de la DOM. Una anàlisi a escala de xarxa fluvial identifica un patró de concentració i diversitat química de la DOM amb màxims en els rius de mida mitjana. En base a aquests resultats, aquesta tesi proposa un marc conceptual per comprendre i predir les dinàmiques espacials i temporals de la DOM fluvial

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Albarello, Sara. "Analisi di parametri di stress ossidativo nel mitilo mediterraneo (Mytilus galloprovincialis) esposto a nano e microplastiche." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/15077/.

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Il lavoro di tesi si colloca all’interno di un progetto più vasto, JPI Ocean PLASTOX Project, volto ad indagare l'ingestione, il trasferimento lungo la catena trofica e l'impatto ecotossicologico delle plastiche sulle principali specie ed ecosistemi marini europei. Lo scopo della presente ricerca è stato quello di valutare la potenziale tossicità delle microplastiche (3 µm) e delle nanoplastiche (50 nm) in Mytilus galloprovincialis, sottoposto ad un dosaggio basso pari a 1,54 ng/L, intermedio pari a 15,4 ng/L, e alto pari a 154 ng/L di polistirene, al fine di ottenere informazioni circa la eventuale dose-risposta, e di correlare eventuali effetti con le dimensioni delle plastiche. L’esperimento è stato condotto in ambiente controllato e protratto per 21 giorni. E’ stata valutata la risposta immunitaria attraverso la misura dell’attività del lisozima e della fagocitosi negli emociti. E’ stata inoltre analizzata una batteria di 6 biomarker, scelti come indicatori di stress ossidativo,i n due tessuti: branchie e ghiandola digestiva. I dati ottenuti mostrano una riduzione dell’attività del lisozima, sia dopo esposizione a micro- che a nanoplastiche ed una riduzione della attività fagocitaria dopo esposizione alle sole microplastiche. L'effetto sull’attività dell’acetilcolinesterasi non appare di rilievo mentre l’attività della catalasi nelle branchie mostra una risposta a campana, con aumento alle basse concentrazioni di contaminanti e diminuzione alle concentrazioni più alte; non c’è effetto sull’enzima nelle ghiandole digestive. L'effetto sull'attività dell'enzima glutatione S-transferasi nelle branchie e nelle ghiandole digestive non è risultata significativa. Si osserva un aumento dell’accumulo della malondialdeide nei tessuti significativo alle dosi maggiori di micro e nanoplastiche. Nell’insieme 21 giorni di trattamento a micro e nanoplastiche inducono moderati effetti ossidanti e riducono la risposta immunitaria anche a concentrazioni ambientali.

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Chapron, Leila. "Response of cold-water corals to global change in the Mediterranean Sea : from the molecular to the reef scale." Electronic Thesis or Diss., Sorbonne université, 2019. http://www.theses.fr/2019SORUS590.

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Les coraux d’eau froide tels que Lophelia pertusa et Madrepora oculata, deux espèces ingénieures cosmopolites, sont d’important constructeurs de récifs, qui abritent une riche biodiversité. Toutefois, ces coraux sont menacés par la pollution et le changement climatique, et ce de manière plus importante en Méditerranée. Des expériences menées in situ au cours de cette thèse révèlent que les deux espèces ont des préférences d’habitat différentes, avec l’environnement moins profond étant plus favorable à M. oculata. Les paramètres hydrologiques influencent la croissance des coraux, sans doute en modulant les apports nutritionnels et les taux de sédimentation dans les profondeurs. Nos travaux en conditions contrôlées montrent des modifications précoces du consortium bactérien et des voies métaboliques chez L. pertusa. Une augmentation de la température réduit sa croissance et ses réserves énergétique. Pour M. oculata, la croissance et le consortium bactérien ne changent pas avec une augmentation de température mais une diminution des réserves énergétique est enregistrée. Finalement, ces travaux de thèse montrent que les macro- et les microplastiques limitent la croissance de L. pertusa probablement en réduisant l’accès à la nourriture dans le cas des macroplastiques et en augmentant les coûts énergétiques liés à l’ingestion et le rejet des microplastiques, alors que M. oculata n’est pas impactée. Ce travail souligne qu’en Méditerranée, où la température de l’eau devrait augmenter de 1.5°C et les plastiques s’accumuler dans les profondeurs, la composition des communautés coralliennes pourrait changer, ce qui aura un impact direct sur la biodiversité associée aux récifs Scleractinian cold-water corals such as Lophelia pertusa and Madrepora oculata, two cosmopolitan engineer species, are important frame-builders that provide ecological niches and nurseries for associated fauna. However, a detailed knowledge of their biology and ecology is still lacking. Such knowledge is important as these corals are threatened by pollution and climate change, especially in the Mediterranean Sea. Experimental in situ studies from this PhD first revealed that the two coral species did not have the same environmental preferences, with M. oculata favoring shallower habitats while L. pertusa did not show marked preferences. Hydrological conditions influenced their growth patterns probably by modulating the quantity and quality of food available in the deep, and by influencing sedimentation rates. Analyses in controlled conditions then showed that L. pertusa’s microbiome and metabolic pathways can change rapidly. However, the temperature increase will reduce L. pertusa’s skeletal growth and energy storage. Madrepora oculata’s skeletal growth and microbiome did not change with temperature increase but their energy storage decreased. Finally, our work showed that exposure to both macro- and microplastics limited L. pertusa’s growth by reducing access to food in one case and by inducing higher energy costs for plastic egestion in the other, while M. oculata did not appear affected to plastic exposure. In conclusion, in the deep Mediterranean Sea where water temperature may increase by 1.5°C during this century, and where plastics accumulate, the composition of coral communities is expected to change, which will have a direct impact on the reef associated fauna

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García, González Raquel. "Towards an improved understanding of the impacts of drought stress on the atmospheric exchange of CO2 and distribution of production in Mediterranean ecosystems." Paris 11, 2009. http://www.theses.fr/2009PA112230.

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L'environnement impose déjà un stress continu de température et de précipitation dans les régions de type Méditerranéen. Ces zones pouraient connaître une réduction des précipitations de plus de 20% au cours de la période estivale en 2090-2099 par rapport à 1980-1999. Cela pourrait avoir des implications importantes parce que les écosystèmes méditerranéens jouent le rôle de transition entre les tropiques et les régions tempérées d'Europe et ils peuvent etre particulièrement sensibles au changement climatique et aux nouvelles prévisions de température et schéma de précipitations. Dans la région de la Méditerranée, les modèles généralement presentent des problèmes dans la représentation des effets du stress hydrique sur l'absorption du carbone par la photosynthèse et les émissions de carbone par la respiration hétérotrophique. Cela a motivé l’étude et la quantification des limitations stomatique et non-stomatique sur la photosynthèse par rapport à le teneur en eau du sol. La conductance stomatique joue un rôle actif afin de réduire la photosynthèse dans les situations ou le deficit en eau du sol est modéré ; neanmoins, quand la sécheresse augmente, les limitations non stomatiques sur la photosynthèse, ainsi que les limitations sur la conductance interne et les limitations biochimiques, peuvent imposer des limitations plus sévères. Ces deux hypothèses ont été évaluées, et leur importance relative a été calculée pour différentes espèces et pour une large gamme de conditions de sécheresse. Les limitations non stomatiques à la photosynthèse dans les conditions de fort stress hydrique ont été jugée prédominantes dans chacune des espèces étudiées. L’application des limitations non stomatiques à la photosynthèse avec le modèle ORCHIDEE ont conduit en moyenne à une réduction de 11% pour la photosynthèse annuel prévue pour une forêt feuillue dans le sud de la France. À l'échelle régionale, cet rapprochement pourrait réduire les taux de photosynthèse et de transpiration, améliorer de l'efficience de l’utilisation de l'eau et la réduction de la perte d'eau par les plantes. Il reste toutefois des incertitudes dues principalement à des différences selon les modèles considérés dans les descriptions des processus de l'écosystème et de l'hydrologie du sol. Suivant, ces modèles sont en désaccord sur quel processus de l’écosystème est à l'origine des anomalies de l’échange net du carbone dan les écosystèmes, dû de une part l'augmentation de la respiration ou de autre part à la reduction de la productivité. La respiration de l'écosystème pourrait être un élément clé dans le contrôle du bilan de carbone dans les écosystèmes méditerranéens The environment imposes a water and temperature stress over time to Mediterranean-type areas. Future climate predictions have warned that these areas may experience a precipitation reduction by more than 20% during the summer period for the period 2090-2099 relative to 1980-1999. This might have important implications because Mediterranean ecosystems act as a transition between tropical and more temperate regions in Europe and they may be especially sensitive to climate change. Indeed, in the Mediterranean region all climate models generally performed poorly most likely because of problems in the representation of water stress effects on both carbon uptake by photosynthesis and carbon release by heterotrophic respiration. Stomatal conductance plays an active role to reduce photosynthesis under moderate soil water deficits, but when drought stress increases, non stomatal limitations on photosynthesis, such as internal conductance and biochemical limitations, may impose higher limitations. These two assumptions were assessed and their relative importance was quantified for different species and for a wide range of drought conditions. Non-stomatal limitations to photosynthesis under water stressed conditions were found to be more dominant in each of the species studied. Applying non-stomatal limitations to photosynthesis with ORCHIDEE model leads on average to an 11% reduction compared with the original model performance in the predicted total photosynthesis over the year for a broadleaf forest site in southern France. At the regional scale it may reduce photosynthesis and transpiration rates, improving the efficiency in the use of water by plants and reducing water loss through plants. But, there are still high uncertainties related to different model descriptions of the ecosystem processes and soil hydrology. In general, models disagree on the dominating ecosystem process causing the anomalous net ecosystem exchange, driven by an increase in respiration or by a decline in GPP. Changes in the precipitation patterns may have important implications to predict future net carbon gain and allocation of Mediterranean ecosystems; it might lead to a reduction in the net C gain through a reduction on the heterotrophic ecosystem respiration

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Mata, Catarina. "Ecophysiology of the Mediterranean oaks Quercus suber and Q. faginea : effects of low temperature with bright light and of water stress on photosynthesis, respiration and water relations = ecofysiologie van de mediterrane eiken Quercus suber en Q. faginea : effecten van de combinatie van lage temperatuur en hoge lichtintensiteit en van water stress op fotosynthese, ademhaling en waterrelaties /." [S.l. : s.n.], 1999. http://www.gbv.de/dms/bs/toc/322603722.pdf.

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Konstantinidou, Valentini. "Molecular mechanisms involved in the protective effect of Mediterranean diet and olive oil consumption in humans." Doctoral thesis, Universitat Pompeu Fabra, 2010. http://hdl.handle.net/10803/7208.

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The scope of the present work was to investigate whether the protective role of the traditional Mediterranean diet (TMD), and virgin olive oil (VOO) rich in phenolic compounds (PC), towards cardiovascular disease can be mediated through gene expression changes. Two trials were performed to assess the in vivo nutrigenomic effects of TMD and VOO in healthy volunteers. The results point out: a) significant gene expression changes of those genes related with cardiovascular-risk processes after VOO ingestion; b) a down-regulation in the expression of atherosclerosis-related genes after a 3-month intervention with a TMD; and c) an olive oil PC health-protective nutrigenomic effect within the frame of the TMD. Changes in gene expression were concomitant with decreases in oxidative damage and systemic inflammation markers. Data from our studies provide further evidence to recommend both the TMD and the VOO as a useful tool for the prevention of atherosclerosis. El objetivo de este estudio es investigar si el papel protector de la dieta Mediterránea tradicional (TMD) y del aceite de oliva virgen (VOO), rico en compuestos fenólicos (PC), puede ser mediado a través de cambios en la expresión génica. Se realizaron dos ensayos clínicos para evaluar los efectos nutrigenómicos de la TMD y del VOO, in vivo, en voluntarios sanos. Los resultados mostraron a) cambios en la expresión génica de genes relacionados con el riesgo cardiovascular tras la ingestión del aceite virgen de oliva, b) una infra-expresión en la expresión de genes relacionados con el proceso aterosclerótico tras una intervención con TMD de 3 meses y c) que los compuestos fenólicos del aceite de oliva ejercen un efecto nutrigenómico protector en el marco de la TMD. Los cambios en la expresión génica fueron coherentes.

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Noyer, Mégane. "Développement d'indicateurs microbiens de multipollutions en Méditerranée : vers un outil d'évaluation de la qualité des eaux douces Particle-attached riverine bacteriome shifts in a pollutant-resistant and pathogenic community during a mediterranean extreme storm event Evolution of the particle-attached riverine archaeome compared to the bacteriome as a result of multipollution following a mediterranean extreme event." Thesis, Perpignan, 2020. http://www.theses.fr/2020PERP0027.

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Les écosystèmes d’eau douce sont très vulnérables face aux perturbations anthropiques. Ils peuvent en effet subir de multiples pollutions via entre autres le lessivage des sols des bassins versants mais aussi la remobilisation des sédiments des lits des rivières et des réseaux d’assainissement, phénomènes accentués lors des épisodes pluvieux, particulièrement intenses et fréquents dans les régions au climat méditerranéen. Lors d’un épisode méditerranéen étudié précédemment, il a été démontré que des déversements de mélanges de polluants se produisaient, coïncidant avec le pic de débit et du débordement des déversoirs d’orage (DDO) qui l’ont précédée. Au cours de cette thèse, nous avons pu vérifier que ces multipollutions sont récurrentes, se produisant à chaque DDO et pic de débit lors de deux autres crues. Nous avons donc émis l’hypothèse que les communautés microbiennes fluviatiles, qui constituent le seul compartiment biologique capable de dégrader les polluants, pourraient être largement impactées par ces multipollutions récurrentes en méditerranée. Cette thèse visait ainsi à déterminer l'évolution du microbiome fluviatile au cours d’événements pluvieux extrêmes, et ce, à travers la modélisation statistique combinant des données de séquençage haut débit à une large panoplie de paramètres environnementaux. Les résultats obtenus démontrent une relation significative entre les multipollutions et l’apport de microorganismes liés à la matière fécale, aux milieux urbains et résistants aux polluants et/ou pathogènes. Ces microorganismes exogènes pourraient affecter fortement les communautés résidentes. Compte tenu de la réaction rapide du microbiome fluviatile face aux multipollutions, nous avons également mis en évidence des microorganismes clés de stress multiple, qui pourraient servir comme nouveaux biomarqueurs à incorporer dans un outil de détection de multipollutions pour le suivi de la qualité des eaux Freshwater ecosystems are highly vulnerable to anthropogenic disturbances. Indeed, they can be subject to multiple forms of pollution via, among other things, the leaching of soil from catchment basins but also the remobilisation of sediment from river beds and sewerage networks, phenomena that are accentuated during rainy episodes, which are particularly intense and frequent in regions with a Mediterranean climate. In a Mediterranean event studied previously, it was shown that discharges of pollutant mixtures occurred, coinciding with the water discharge peak and combined sewer overflows (CSO) that preceded it. During this thesis, we were able to verify that these multipollutions are recurrent, occurring at each CSO and water discharge peak along two other floods. We hypothesised that fluvial microbial communities, which constitute the only biological compartment able to degraded pollutants, could be largely impacted by these recurrent multipollutions in Mediterranean. This thesis aimed to determine the impact of pollutant mixtures on the evolution of the fluvial microbiome during extreme rainfall events via statistical modelling coupling high throughput sequencing data to a wide range of environmental parameters. Results showed a significant relationship between multipollutions events at CSOs and water discharge peak and the appearance of microorganisms linked to faecal matter, urban environments and resistant to pollutants and/or pathogens, which could strongly affect riverine resident communities. Given the rapid response of the fluvial microbiome to multi-pollutants, we were able to identify key multi-stress microorganisms, that could be used as new biomarkers to be incorporated into a multi-pollutant detection tool for water quality monitoring

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Mandarić, Ladislav. "Transport, distribution and fate of emerging contaminants in wastewater-receiving rivers under multiple stress conditions." Doctoral thesis, Universitat de Girona, 2018. http://hdl.handle.net/10803/666341.

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The main aim of this thesis was to establish a link between the urban origin of chemical contamination (e.g. PhACs) and other stressors, particularly associated to water scarcity (Chapter 1, 2, and 3). Research has been performed in one Alpine (Chapter 1) and two Mediterranean river basins (Chapter 2 and 3). Effects of the river flow variability on the recovery potential of the rivers (natural in-stream attenuation) have been studied in the tributary streams of the lower Ebro River (Chapter 2) and the Evrotas River (Chapter 3). Results have shown that occurrence and spatiotemporal distribution of PhACs in the fragile Alpine and Mediterranean aquatic environments is subjected to a strong intra-annual variability of the stream flow, while effects of multiple stress conditions may be amplified under water scarcity conditions (e.g. drought), thus resulting in the increased concentrations levels of PhACs in river water and sediments L'objectiu principal d'aquesta tesi ha estat establir un vincle entre l'origen urbà de la contaminació química (per exemple, els PhACs) i altres estressors, particularment associats a l'escassetat d'aigua (capítols 1, 2 i 3). Les investigacions s'han realitzat en un riu Alpi (Capítol 1) i dues conques del Mediterrani (Capítol 2 i 3). Els efectes de la variabilitat del flux fluvial sobre el potencial de recuperació dels rius (atenuació natural) han estat estudiats en rius del baix riu Ebre (capítol 2) i del riu Evrotas (capítol 3). Els resultats mostren l'aparició i la distribució espaciotemporal dels PhACs en els fràgils entorns aquàtics alpins i mediterranis, sotmesos a una forta variabilitat intra-anual del flux, mentre que els efectes de múltiples condicions d'estrès poden ser amplificades sota condicions d'escassetat d'aigua, que afavoreixen concentracions més elevades de PhACs en aigües i sediments

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Vázquez, Garcia Eusebi. "Influence of hydrology on dissolvedorganic matter quantity and properties in a temporal Mediterranean stream = Influència de la hidrologia sobre la quantitat i disponibilitat de la matèria orgànica dissolta en una riera temporal mediterrània." Doctoral thesis, Universitat de Barcelona, 2013. http://hdl.handle.net/10803/128863.

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The studies presented in this thesis focus on the biogeochemistry of dissolved organic matter (DOM) in an intermittent stream in a Mediterranean climate zone, with great emphasis on extreme hydrologic events: floods and the seasonal drought period. The changes in concentration and molecular weight, and the properties, especially those related to its origin, and bioavailability to the microbial community. The samplings were carried out during a wide span of years in order to characterize the concentration – discharge responses (C-Q) initially, and more intensively during the different periods of the hydrologic year (wet, drought and transitional periods) in order to capture the widest possible picture of the dissolved organic matter dynamics and processing. The last chapter is a review of different fluorescence spectroscopy and UV-vis absorbance methods applied in DOM characterization. The main conclusions from these works are: 1. The most probable C-Q response types represent only a 40% of all cases from the data set. Therefore, the majority of DOC and NO3-Q responses fall within some low probability C-Q response types. 2. The dry-wet transition does not present a typical C-Q response. Instead, it promotes the diversity of DOC-Q responses. The 33% of events comprised during this period contribute to the 41% of the total DOC-Q response diversity. On the other hand, it does not enhance NO3-Q responses. 3. The most important driver for the succession of NO3-Q responses is the periodicity of the magnitude of storms (ΔQ) is, while the effect of the seasonal temperature change (i.e., Tday), appears more perceptible after the removal of the signal of the weaker and more frequent rain episodes. 4. The occurrence of a severe summer dry period favored the mobilization and transport of labile DOC, as shown by the 56% of retention across the stream – riparian interface, during the following hydrological transition period. Furthermore, the DOC retention during this period was preferential from high to low molecular weight fractions. In the case of no apparent hydrological transition all DOC molecular weight fractions were equally conservative. 5. During both drought and rewetting periods DOC and DON bioavailability are not tied to a MW fraction. During the rewetting period, although there is no clear pattern of bioavailability according to any DOC MW fraction, 50% of cases at which DOCMW release is observed (BDOCMW<0) correspond to the LMW fraction. 6. In general, DOCMW dynamics fit within the framework that storm events enhance the input of larger molecular weight DOC fraction (higher than 1 kDa), but DONMW does not. Furthermore, the hydrologic characteristics of the rewetting period evidence an asynchronous mobilization of DOC and DON. 7. DOC bioavailability is heavily influenced by DON content rather than molecular weight. Furthermore, bioavailability seems to be regulated by the DOC:DON ratio presenting a threshold value of 13. The most remarkable case is that of DOCLMW that shifts from refractory to bioavailable when its DOC:DON ratio is lower than 13. 8. Drought causes a gradual hydrological fragmentation of the fluvial network enlarging the variability of DOM properties, and amplifying the biogeochemical variability of a fluvial system. 9. Sampling sites with lotic water bodies in summer show DOM properties similar to those observed in autumn under base flow hydrological conditions and reflect the prevalence of terrestrial inputs. In contrast, in isolated and lentic water bodies, DOM analyses reveal a supplementary contribution of autochthonous organic matter, originated by in situ microbial processes. 10. BDOC estimated during summer indicates an upper threshold of 40% that is also observed during the rewetting period. This allows asserting that the highest bioavailable DOC concentration can be reached during two ecosystem perturbations of opposite sign. Els articles presentats en aquesta tesi es centren en els aspectos biogeoquímics de la materia orgànica dissolta (DOM) en una riera temporal en una zona de clima mediterrani. Concretament, s’estudien els efectes dels events hidrològics extrems, les crescudes i les sequeres estacionals pròpies de la regió mediterrània, en la concentració i les propietats de la matèria orgànica dissolta. Els paràmetres utilitzats en la caracterizació de la DOM permeten principalment establir l’origen d’aquesta i establir la seva biodisponibilitat per a les comunitats microbianes del riu. En l’aspecte quantitatiu també es realitza un estudi més detallat mitjançant el fraccionament en diferents rangs de pes molecular. La recollida de dades inclou una sèrie temporal llarga que permet estudiar les despostes concentració – cabal (C-Q) tant del carboni orgànic dissolt com del nitrat, i d’uns mostreigs de camp intensius que permeten obtenir una imatge precisa dels diferents períodes de l’any hidrològic (període humit, de sequera i de transició hidrològica). Els resultats d’aquests treballs permeten copsar la variabilitat de les respostes C-Q, que en el cas del DOC veuen augmentada la seva variabilitat durant el període de transició hidrològica. En el cas del nitrat s’observa que les respostes es troben relacionades amb la magnitud y l’interval de temps entre episodis de precipitació. Pel que fa a la biodisponibilitat de les diferents fraccions moleculars, mentre que els estudis inicials apunten a una immobilització selectiva de les fraccions més grans a la interfase ripariana, estudis següents postren que la concentració de nitrogen orgànic dissolt és cabdal a l’hora de determinar si una fracció és biodisponible o no. A nivell hidrològic es conclou que tant durant la transició hidrològica com durant el període de transició hi ha una amplificació dels processos biogeoquímics que permeten estudiar el sistema fluvial amb més profunditat. No obstant, durant la fragmentació hidrològica es produeix una augment en la variabilitat biogeoquímica mentre que durant la transició hi ha una tendencia a l’homogeneïtzació.

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Fenollosa, Romaní Erola. "Estrès, reproducció i senescència en l’èxit invasor: l’estudi de cas de Carpobrotus edulis." Doctoral thesis, Universitat de Barcelona, 2020. http://hdl.handle.net/10803/672246.

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Les espècies exòtiques invasores constitueixen una de les majors amenaces a la biodiversitat global. Aquelles àrees que acullen un gran nombre d’espècies natives, i constitueixen per tant punts calents de biodiversitat tals com la conca Mediterrània, són especialment sensibles a aquests agents de canvi. Carpobrotus edulis és una espècie clonal àmpliament distribuïda arreu del món que ha esdevingut invasora a les regions mediterrànies, on provoca la reducció de la biodiversitat nativa alterant les propietats fisicoquímiques del sòl. L’objectiu de la tesi és entendre els mecanismes fisiològics que determinen l’èxit invasor de l’espècie a la conca Mediterrània, relacionant les respostes a l’estrès, a la reproducció i a la senescència, que en conjunt defineixen la història vital de l’espècie. Els resultats obtinguts mostren que C. edulis es troba adaptada a les condicions ambientals de la conca Mediterrània gràcies a la seva gran plasticitat fisiològica en resposta a la baixa disponibilitat hídrica característica de l’estiu i les baixes temperatures característiques de l’hivern, els dos moments més durs per a la vegetació durant l’anualitat en aquesta regió. El model de distribució de l’espècie construït juntament amb la major tolerància a les baixes temperatures que presenten els individus de C. edulis del rang invasor revelen que la capacitat de l’espècie per a tolerar l’estrès resulta crucial per a la seva invasió a Europa. C. edulis és una espècie clonal monocàrpica a nivell de ramet però policàrpica a nivell de genet. Aquesta estratègia constitueix un procés de senescència adaptativa ja que la mort del ramet facilita el creixement a les següents generacions. L’elevat esforç reproductor de l’espècie, l’elevada producció de llavors i la seva gran longevitat contribueixen a la formació d’un banc de llavors persistent que incrementen l’impacte de l’espècie i la seva persistència. La variabilitat en els atributs relacionats amb la reproducció sexual genera diferències en les dinàmiques del banc de llavors en diferents localitzacions dins del rang invasor. Aquesta variabilitat a diferents escales contribueix a l’èxit de l’espècie a través de l’optimització de recursos, la resiliència a pertorbacions i a través de permetre processos adaptatius a nivell d’individu. En conjunt, la invasió de C. edulis a la conca Mediterrània és conseqüència d’un procés de retroalimentació positiva d’expansió i impacte a través de la interacció entre la tolerància a l’estrès, l’esforç reproductor i la senescència adaptativa. Aquestes relacions i dinàmiques poden contribuir a la delimitació d’àrees prioritàries per l’erradicació de C. edulis en el territori. En conclusió, la invasió de C. edulis ha estat possible no només gràcies a atributs tals com el creixement clonal, l’elevat esforç reproductor, la formació d’un banc de llavors persistent, els cicles de vida curts i l’elevada plasticitat; sinó també gràcies a factors relacionats amb el factor humà com la degradació ecosistèmica i l’elevada pressió de propàgul associada a l’interès ornamental de l’espècie. Invasive species constitute one of the main threats to global biodiversity. Especially those areas hosting a huge number of native species, such as the Mediterranean basin, are sensitive to these change drivers. Carpobrotus edulis is a widespread clonal invasive species that has become invasive at the Mediterranean basin reducing native biodiversity by strongly impacting the physicochemical soil properties. We aimed to understand C. edulis invasive success through an ecophysiological approach by understanding the relationships between its stress tolerance, reproduction capacity and the role of senescence in its fitness, which together define the species’ life history strategy. Our results showed that C. edulis is adapted to the Mediterranean basin environmental conditions showing a high physiological plasticity in response to drought and chilling, the most sensitive periods along the year in the Mediterranean area. The species stress tolerance was crucial to invade Europe as revealed by the projected species distribution model and the increased chilling tolerance found in C. edulis invasive individuals. C. edulis is a monocarpic clonal species at the ramet level but polycarpic at the genet level, which constitutes and adaptive senescence process to growth facilitation to the next generations. High reproductive effort, seed production and seed longevity contribute to the formation of a persistent seed bank for this species increasing its impact and persistence potential. Seed trait variability across the invaded range generates differential soil seed bank dynamics that may be considered for improving management policies. This variability at different scales may contribute to species success by resource optimization, perturbation resilience and allowing adaptation. Overall, the C. edulis invasion at the Mediterranean basin results from a positive feedback of expansion and impacts through the interaction of species stress tolerance, reproductive effort and adaptive senescence. We conclude that the invasion of C. edulis in Europe has been possible not only by its ideal traits such as clonality, strong reproductive effort, the formation of a persistent soil seed bank, short life cycles and high plasticity, but also thanks to human factors such as the strong propagule pressure associated with its ornamental interest.

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Milano, Marianne. "Changements globaux en Méditerranée : impacts sur le stress hydrique et la capacité à satisfaire les demandes en eau." Thesis, Montpellier 2, 2012. http://www.theses.fr/2012MON20080.

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La région Méditerranéenne a été identifiée comme l'une des régions les plus vulnérables aux changements climatiques et anthropiques et constitue un des « hot-spots » mondiaux de crise de l'eau. Dans un tel contexte, les questions relatives à la gestion des ressources en eau se posent de manière accrue. Pour y faire face, des approches de modélisation intégrée associant l'évaluation de la disponibilité des ressources en eau et des demandes en eau sont proposées. Une chaîne méthodologique a été mise en place à l'échelle régionale, considérant des scénarios hydrologiques et d'usages de l'eau sous contraintes climatiques et incluant les objectifs de la Stratégie Méditerranéenne pour le Développement Durable en termes d'efficience hydraulique. Cette première approche permet d'évaluer la situation du stress hydrique en Méditerranée et son évolution à l'horizon 2050. Actuellement, le Sud et l'Est de la Méditerranée doivent faire face à un stress hydrique sévère, voire à une pénurie. D'ici 2050, les ressources en eau disponibles pourraient diminuer de l'ordre de 30 à 50 % tandis que les prélèvements devraient doubler. Le stress hydrique devrait ainsi augmenter sur l'ensemble du pourtour méditerranéen. Néanmoins, si les objectifs d'efficience sont atteints, les prélèvements en eau pourraient se stabiliser, voire même diminuer (10–40 %) dans certains bassins Nord méditerranéens. Le stress hydrique pourrait alors rester faible sur la rive Nord et être tempéré dans certains bassins de la rive Est. Une deuxième chaîne méthodologique a été développée à l'échelle du bassin de l'Ebre (Espagne) afin d'appréhender la satisfaction des demandes en eau environnementales, domestiques et agricoles. Le bassin a été divisé en 9 sous-bassins versants afin de considérer les différentes contraintes hydro-climatiques et l'influence des barrages principaux sur les régimes hydrologiques, auxquels ont été associés 11 sites de demande. Cette approche permet de définir les pressions actuelles sur le bassin et d'évaluer l'évolution de la capacité à satisfaire les demandes en eau sous contrainte de scénarios climatique, d'évolution démographique et d'expansion des surfaces irriguées à moyen terme. Actuellement, les demandes en eau sur le bassin versant de l'Ebre sont satisfaites. A l'horizon 2050, les écoulements printaniers et estivaux pourraient diminuer de 30 à 35 % en différents points du bassin. Les demandes en eau environnementales et domestiques devraient toujours être satisfaites, néanmoins, la capacité à satisfaire les besoins agricoles pourrait ne pas toujours être assurée au cours de la période estivale. Ces deux démarches établissent une confrontation entre l'offre et la demande en eau à différentes échelles et fournissent des indicateurs sur la capacité à satisfaire les demandes en eau sous contraintes climatiques et anthropiques. Elles constituent ainsi des approches originales pour évaluer la disponibilité actuelle et future des ressources en eau, identifier les régions où des tensions d'usages risquent de se produire et mieux orienter les stratégies d'adaptation. Dans un contexte de changements globaux, ce type d'exercice est fondamental pour soutenir les politiques de gestion de l'eau et encourage la co-construction de scénarios entre usagers, décisionnaires et scientifiques The Mediterranean basin has been identified as one of the world's most vulnerable regions to climatic and anthropogenic changes and constitutes a water crisis' hot spot. Under such context, questions on water resources management arise. Integrated methodologies taking into account evolution in water resources availability and water demands are thus generated. A first methodology accounting for the Mediterranean basin specific conditions is developed to assess the current and future water stress state of this region. The medium-term evolution of water stress is investigated using climatic scenarios and a water-use scenario based on efficiency improvements following the recommendations of the Mediterranean Strategy for Sustainable Development. Currently, the southern and eastern rims are experiencing high to severe water stress. By the 2050 horizon, a 30–50% decline in freshwater resources is simulated over most of the Mediterranean basin and total water withdrawals are projected to double. Water stress could hence increase over the whole Mediterranean basin. If progresses in efficiency are reached, total water withdrawals would stabilize over the Mediterranean basin and even make them decrease (10–40%) in many northern catchments. Water stress could thus be tempered in some eastern catchments and kept to low on the northern rim. A second integrated water resources modelling framework was developed over the Ebro catchment (Spain) in order to evaluate water allocation for the domestic and agricultural sector as well as for environmental purposes. The catchment was divided into 9 sub-catchments to which 11 demand sites were attributed, in order to take into account the different hydro-climatic regimes and the influence of dams on hydrological regimes. This method defines current pressures applied to water resources and evaluates the evolution of water allocation by the medium term under climatic and water-use scenarios considering population growth and irrigated areas expansion. Currently, water demands are satisfied over the Ebro catchment. In 2050, water resources are projected to decline by 30-35% during the spring and summer seasons. Environmental and domestic water demands should still be satisfied but agricultural water demands could have to face severe water shortages during the summer season. These two modeling frameworks establish a dialogue between water resources and water demands at different space scales and give indexes on the capacity to satisfy water demands under climatic and anthropogenic scenarios. These studies provide original approaches to evaluate water resources current and future availability, to identify the most vulnerable regions to water use conflicts and to better orientate adaptation strategies. In a context of climatic and anthropogenic changes, such frameworks are a first step to better sustain water management policies and to support the co-construction of scenarios between users, policy-makers and scientists

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Karray, Sahar. "Etude écotoxicologique et phylogéographique de la coque Cerastoderma glaucum issue du Golfe de Gabès : réponse adaptative (in situ et in vivo) au stress métallique et structure génétique." Thesis, Le Mans, 2015. http://www.theses.fr/2015LEMA1007/document.

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Cerastoderma glaucum est un modèle biologique de choix pour des études phylogéographiques et écotoxicologiques.Une étude de sa structure génétique en méditerranée occidentale a été réalisée en utilisant deux types de marqueurs, mitochondrial et nucléaire. Les résultats obtenus ont révélé à travers l’ADN mitochondrial une population très divergente de toutes les autres populations (Ellouza, Sud de la Tunisie).Une étude écotoxicologique sur des populations issues de ce site Ellouza et deux autres sites à proximité dans la région du golfe de Gabès a été réalisée dans le but d’étudier la réponse adaptative des populations de la coque C. glaucum en milieu naturel à différents niveaux de l’organisation biologique allant du niveau individuel jusqu’au niveau cellulaire et moléculaire. En parallèle à cette étude, deux expérimentations en laboratoire ont été réalisées afin de préciser les mécanismes pouvant expliquer le succès ou l’échec du maintien des populations de C. glaucum. La première expérimentation a été réalisée en utilisant des effluents industriels et la deuxième en utilisant un contaminant pur le cadmium. Les niveaux de l’organisationbiologique concernés par cette étude étaient le niveau individuel et le niveau moléculaire. Différents biomarqueurs impliqués dans la réponse à différents types de stress : (MT), (ABCB1), (MnSOD et CuZnSOD), (CAT), (HSP70) et (COI) ont été utilisés en milieu naturel ainsi qu’en conditions contrôlées et les résultats obtenus ont montré l’importance dumétabolisme énergétique dans la réponse au stress quelque soit l’approche utilisée (in situ/ expérimental) à travers la régulation de l’expression du gène COI Cerastoderma glaucum is an adequate biological model for phylogeographic and ecotoxicological studies.A study of its genetic structure in the Western Mediterranean sea was conducted using two markers types: mitochondrial and nuclear. The DNA mitochondrial marker results show a divergent population from all the other ones (Ellouza South ofTunisia).An ecotoxicological study of populations sampled from Ellouza site and two other nearby sites in the Gulf of Gabes region was carried out in order to study the adaptive response of natural populations of C. glaucum at different levels of biological organization from the individual level to the cellular and molecular ones. In parallel, two laboratory experiments were performed to clarify the mechanisms that may explain the success or failure of maintaining populations of C. glaucum. In thefirst one, industrial effluents were used and in the second we have used a pure contaminant, the cadmium. These studies experiments concerned individual and molecular levels. Different biomarkers involved in the response to different types of stress: (MT), (ABCB1) (MnSOD and CuZnSOD) (CAT) (HSP70) and (COI) were used in natural and exposed cockles.Results showed the importance of energy metabolism in response to stress whatever the used approach (in situ / Experimental) through the regulation of the expression of the COI gene

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Affholder, Marie-cecile. "Approche des mécanismes de tolérance du romarin aux éléments traces métalliques et métalloïdes : perspectives pour une phytostabilisation des sols méditerranéens pollués." Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4730/document.

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Les conséquences des activités industrielles passées, et notamment métallurgiques, persistent encore aujourd'hui. C'est le cas dans l'actuel Parc National des Calanques, qui abrite l'ancienne fonderie de plomb de l'Escalette (sud-est de Marseille). Ainsi, plus de 80 ans après la fermeture de cette usine, une contamination importante et étendue en éléments traces métalliques et métalloïdes (ETMM) est présente. Les objectifs de cette thèse ont été de contribuer à l'évaluation de la contamination diffuse en ETMM des sols des Calanques situés aux alentours du site industriel abandonné de l'Escalette. Dans un but futur de restauration écologique, solution adaptée dans le contexte particulier de la zone de pollution diffuse, située dans le Parc National des Calanques, les capacités d'accumulation et les mécanismes de tolérance d'une espèce autochtone, le romarin (Rosmarinus officinalis) ont été étudiés. Ainsi, cette étude a permis de mettre en évidence quelques mécanismes de tolérance aux ETMM certainement mis en jeu dans le cas du romarin. Les résultats montrent que le romarin pourrait être un candidat intéressant pour la phytostabilisation aux vues de sa capacité d'accumulation des ETMM dans les racines, ainsi que sa résistance à des niveaux de contamination très élevés Past industrial activities, particularly metallurgical one, have current environmental consequences. As an example, the former lead smelter from l'Escalette (South-East Marseille, France) in the National Park of Calanques lead to an important environmental pollution of its surroundings. Thus, more than 80 years after its activity ceased, a trace metal and metalloide (TMM) diffuse pollution is still present. This PhD study aimed to contribute to the assessment of the diffuse contamination levels by TMM of the Calanque's soils around the former lead smelting factory. Aiming at identifying an adapted solution of ecological restoration of the areas with diffuse pollution located in the National Park of Calanques. Accumulation abilities and tolerance mechanisms of a native plant species, rosemary (Rosmarinus officinalis), were studied. In order to achieve this, in situ and ex situ assays were performed. TMM concentrations in rosemary organs (leaves, stems, roots) and some stress phytometabolites were assessed. Moreover, the role of mycorrhizal symbioses in rosemary tolerance was evaluated

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Celis, Plá Paula Soledad María. "Vulnerability and acclimation of Mediterranean Sea macroalgae, to environmental stress related to climate change: use of indicators physiological state = Vulnerabilidad y aclimatación de macroalgas del Mar Mediterráneo, frente al estrés ambiental derivado del Cambio Climático: uso de indicadores del estado fisiológico." Doctoral thesis, Universitat de Barcelona, 2015. http://hdl.handle.net/10803/313995.

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In this thesis, the vulnerability and capacity of acclimation to environmental stress related to Climate change mainly in Cystoseira tamariscifolia and other species as Ellisolandia elongata, Cystoseira compressa and Padina pavonica are evaluated. The effects of physical stressors as elevated irradiance of PAR (lambda=400-700 nm) and UVR (lambda=280-400 nm) and temperature and chemical stressors as nutrient, heavy metals and CO2, separately and in interaction with different levels were evaluated. Six experimental studies were conducted under varying irradiance, temperature, nutrient conditions, acidification and heavy metals. The common approach in these studies was the use functional bioindicators to evaluate the physiological state macroalgal species of Mediterranean Sea (Alboran Sea) in studies conducted both in situ in ultra-oligotrophic (Cabo de Gata-Níjar Natural Park, Almeria) and oligotrophic waters (La Araña beach, Malaga) and with algae transported to controlled experimental systems under out-door conditions. In addition, an indoor experiment study was performed in Cystoseira tamariscifolia collected in the North Atlantic Ocean, the northern limit of distribution of this species. In this study, the decrease of maximal quantum yield and electron transport rate , the increase of phenolic compounds and antioxidant activity or the increase of C:N ratio are produced in stress conditions and thus they are validated as stress indicator. In addition, it is possible to evaluate the direction of the physiological response i.e. positive or negative to expected changes under climate change factors or other anthropogenic impacts, as eutrophication (increased nitrate levels in the water column) or pollution by heavy metals. However, on the other hand, the increase of phenolic compounds is also produced under increased photosynthetic activity showing a link between antioxidant and algal production. This not a strange result since a high photosynthetic activity is related to a high oxygen production which can be produced oxidative stress. Non-photochemical quenching, oxygen consumption through Mehler reaction and increased antioxidant activities are down regulation mechanisms to survive under promoted oxygenic scenario. Phenolic accumulation under increased nitrate and CO2 levels or the release of phenols under increased irradiance in C. tamariscifolia shows us that this species has effective biochemical mechanisms to acclimate for the expected variations in climate change factors although this is limited by temperature. Phenolic compounds are related to secondary metabolism but in C. tamariscifolia but the direct positive relation found with photosynthetic activity and internal nitrogen in all experiments seem to link the phenols to primary metabolism. In summary, increased CO2 under high irradiance, but not photoinhibitory, conditions will be favorable growth and physiological responses. The nitrate enrichment reduced stress provoked by irradiance or pollution by Cooper due to the photoprotection mechanisms are favored by nitrate increase. However, the positive effect of CO2 and nitrate is dependent on temperature, summer temperature in the field or 4oC increased temperature in outdoor experiments provoked physiological stress. Consequently, ocean acidification will be favorable for C. tamariscifolia only under no very high increase of temperature, less 2-3ºC and without nutrient limitation. The oligotrophication produced in certain areas of Mediterranean Sea will be unfavorable for Cystoseira tamariscifolia communities in a climate change scenario. The data on vulnerability and acclimation to climate change factors of Cystoseira tamariscifolia, Ellisolandia elongata and Padina pavonica presented in this study can help the management of macroalgal communities, mainly in protected areas. In addition, the physiological and biochemical data will help to predict the effects of climate change on bioactive compounds with antioxidant capacity and their potential biotechnological uses as phenolic compounds, mycosporine like aminoacids and carotenoids. En esta tesis, se evaluó la vulnerabilidad y la capacidad de aclimatación al estrés ambiental, relacionada al cambio climático, en las especies Cystoseira tamariscifolia, Ellisolandia elongata, Cystoseira compressa y Padina pavonica. En estas especies, se evaluaron los efectos de los factores de estrés físico, como la irradiancia elevada de PAR (lambda = 400-700 nm) y UVR (lambda = 280-400 nm), la temperatura y factores de estrés químico, como nutrientes, metales pesados y CO2. Se realizaron seis estudios experimentales variando irradiancia, temperatura, condiciones de nutrientes, acidificación y metales pesados. El enfoque común en estos estudios fue el uso bioindicadores funcionales como; rendimiento cuántico máximo de PSII (Fv/Fm) como un indicador de estado fisiológico de macroalgas y de la fotoinhibición, la tasa de transporte de electrones (ETR) como un indicador de la capacidad fotosintética. Como indicadores bioquímicos se utilizaron; las relaciones estequiometrias (C:N) como indicador del estado nutricional y el contenido de compuestos fenólicos y micosporinas, tales como sustancias fotoprotectoras y antioxidantes. Con el objetivo de evaluar el estado fisiológico de estas especies de macroalgas en el Mar Mediterráneo (Mar de Alborán). La disminución del rendimiento cuántico y la tasa máxima de transporte de electrones, el aumento de compuestos fenólicos y actividad antioxidante o el aumento de la relación C: N se producen en condiciones de estrés y por lo tanto, estas variables se validan como indicadores de estrés. Sin embargo, se encontró un aumento de los compuestos fenólicos y de la actividad fotosintética, que muestra una relación entre la actividad antioxidante y la producción algal. Este no es un resultado extraño ya que una alta actividad fotosintética se relaciona con una producción alta de oxígeno lo que puede producir estrés oxidativo. La acumulación de compuestos fenólicos en condiciones de aumento de los niveles de nitrato y de CO2 o la liberación de fenoles bajo mayor radiación solar en C. tamariscifolia, nos muestra que esta especie tiene mecanismos bioquímicos eficaces para aclimatarse a las variaciones esperadas en los factores del cambio climático aunque esté limitado por la temperatura.

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Pailler, Alexia. "Les relations sol/plantes en forêts méditerranéennes : approche bioclimatique des déterminants de la structuration fonctionnelle des communautés microbiennes des sols et de leurs réponses à un double stress hydrique et thermique en région provençale calcaire." Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4344/document.

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En contexte forestier méditerranéen au sein de la région provençale calcaire (sud de la France), les relations sol/structure fonctionnelle catabolique des communautés microbiennes/communautés végétales ont été abordées selon différentes échelles bioclimatiques : un gradient latitudinal et altitudinal, et une échelle écosystémique restreinte à différentes séries de chênes pubescents. Ces travaux ont permis d’estimer les contributions respectives (et de leurs interactions) de la structure et de la composition de la végétation et des variables abiotiques dans la détermination des propriétés fonctionnelles des communautés microbiennes des sols. Dans le contexte des changements climatiques globaux, cette même stratégie a été mise en œuvre pour estimer les incidences, sur les potentiels cataboliques et les profils fonctionnels, d’un double stress hydrique et thermique ex situ, mimétique d’une vague de chaleur. Pour les diverses échelles spatiales, nos résultats ont mis en évidence la prépondérance de la part d’interaction entre la végétation et les variables abiotiques épigées et hypogées dans la structuration fonctionnelle des communautés microbiennes. Suite au stress, une diminution globale de leurs potentiels cataboliques a pu être observée. Néanmoins, nos résultats ont révélé une robustesse différentielle des relations entre la végétation et la structure fonctionnelle des communautés microbiennes selon le stade d’évolution de la végétation et de la nature des espèces constitutives de ces formations au niveau de leur dynamique d’occupation spatiale. Ceci pourrait atténuer ou exacerber les effets du réchauffement climatique sur les écosystèmes forestiers méditerranéens In Mediterranean forest ecosystems in the limestome-based Provence area (south of France), soil-microbial community functional catabolic structure-vegetation relationships were assessed based on different bioclimatic scales, across a latitudinal gradient, an elevation gradient, and at a restricted ecosystemic scale focusing on Pubescent oak forest stands. The respective parts (and their interactions) of the vegetation composition and structure and the abiotic variables in their functional profiles were investigated. Furthermore, in the context of climate change, this same strategy was used to investigate the effects of an ex situ water and thermic stress, mimetic to a heatwave event on microbial community catabolic potentials and functional profiles. For all the considered scales, our results highlighted the major part of the interactions between vegetation and abiotic aboveground-belowground variables in the determination of soil microbial community functional structure. Drought induced a decrease in their potential catabolic activities. Nevertheless, our results revealed a varying robustness of the interactions between vegetation and soil microbial functional structure based on the dynamic step of the evolution of the forest stands and on the type of their constitutive species. This may mitigate or exacerbate climate change effects on Mediterranean forest ecosystems

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Silva, Flávio Daniel Gomes da. "Variações anátomo-fisiológicas face à aclimatação sazonal - estudo em vacas leiteiras com diferente potencial leiteiro." Master's thesis, Universidade de Évora, 2015. http://hdl.handle.net/10174/18742.

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O presente estudo teve como objetivo a caracterização de variações anátomo-fisiológicas que decorrem do processo de aclimatação sazonal em bovinos leiteiros com alto (Altas) e baixo (Baixas) potencial leiteiro, com vista a selecionar animais que conciliem bons desempenhos produtivos e índices de adaptabilidade que possibilitem a mudança de homeostase face às condições climáticas presentes no clima mediterrânico. O estudo foi realizado numa herdade comercial, situada no Alentejo, utilizando 13 vacas multíparas (6 Baixas e 7 Altas), durante três períodos: P1 (animais aclimatados ao verão; presença de stresse térmico); P2 (animais aclimatados ao verão; termoneutralidade); P3 (animais aclimatados ao inverno; termoneutralidade). Em stresse térmico (P1), verificaram-se maiores esforços termolíticos e maiores armazenamentos de calor no grupo das Altas. Observou-se também que a produção de leite das Altas foi afetada pelo stresse térmico, evidênciando uma redução 24-48h após os valores de temperatura retal mais elevados. Nesta situação, as Baixas apresentaram uma variação na produção oposta à das Altas. Em P1, os valores de proteína e de gordura no leite foram significativamente mais baixos que em P3, em ambos os grupos. A ureia no leite foi significativamente mais elevada nas Altas durante o P1, revelando potencial como biomarcador de stresse térmico. Do P1 para o P3 obser-vou-se uma redução gradual do hematócrito, da hemoglobina e da triiodotironina (T3). As Altas apresentaram uma maior redução de triiodotironina (T3) que as Baixas, como consequência de uma maior intensidade de aclimatação. Nos pelos não se registaram diferenças entre os períodos, o que contrasta com alguma bibliografia. Porém, a ausência da insolação direta poderá ter sido um fator determinante; ABSTRACT: The main objective of the present study was the characterization of anatomical and physiological variations that occur in the seasonal acclimatization process of dairy cows with high (Altas) and low (Baixas) milk yield potential. In this way it should be possible to do a selection of animals with good productive traits and also with adaptability indexes that allow a change in homeostasis to cope with the climatic conditions of the mediterranean climate. Meteorological, clinical, productive, physiological and anatomical data were collected. The study was conducted in an Alentejo's dairy farm, using 13 multiparous cows (6 with low milk yield and 7 with high milk yield), during three periods: P1 (animals acclimated to summer, in heat stress); P2 (animals acclimated to summer, thermoneutrality); P3 (animals acclimated to winter; thermoneutrality). In thermal stress (P1), the high milk yield group (Altas) shown greater thermolytic efforts and also higher heat storage. The milk yield in this group was also affected by heat stress, showing a decrease in production when the rectal temperature increased, with a delay of 24-42 hours. In this situation the Baixas group showed an opposite milk production variation. In P1, the protein and fat milk content was lower than in P3, in both groups. Milk urea levels were significantly higher during P1 in the Altas group, revealing potential as an heat stress biomarker. Hematocrit, hemoglobin and triiodothyronine (T3) values gradualy decreased from P1 to P3. T3 values were lower in Altas than in Baixas group, as a consequence of a more intense acclimatization. The hair analysis didn’t show the standard seasonal acclimatization process, indicating the absence of direct solar radiation as a determinant factor.

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Santos, João Pedro Valente e. "Ecology and physical condition of red deer in the Iberian Peninsula: implications for management." Doctoral thesis, Universidade de Aveiro, 2015. http://hdl.handle.net/10773/15765.

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Doutoramento em Biologia The red deer (Cervus elaphus) is currently one of the most widespread and abundant wild ungulates in the Iberian Peninsula and is extremely important both ecologically, as a key species for the functioning of the ecosystems, and economically, as a major game species. In Iberia, red deer populations are subjected to different management systems that may affect the physical condition of the individuals, with further consequences for population dynamics. Studies investigating the effects of management practices and environmental conditions on the performance of red deer are still rare regarding Mediterranean ecosystems. Much of the knowledge concerning the ecology of red deer and the impact of management on its physical condition is based on studies conducted in northern and central regions of Europe, where climatological features and management practices differ from those observed in the Mediterranean areas of Iberia. Studies on a biogeographical scale can provide important insights into the relationships between species and a particular environment and contribute to the development of more targeted and appropriate management practices. The optimisation of sampling procedures and the fine-tuning of pre-existing analytical techniques are also fundamental to a more cost-effective monitoring and, therefore, are of enormous value to wildlife managers. In this context, the main aims of this thesis were: 1) to optimise the procedures used to assess the physical condition of red deer; and 2) to identify relevant management and environmental factors affecting the nutritional condition and stress physiology of red deer in the Mediterranean ecosystems of Iberia, as well as any potential interactions between those factors. Two studies with a methodological focus, presented in the first part of the thesis, demonstrated that the physical condition of red deer can be evaluated more simply, using more cost- and time-effective procedures than those traditionally used: i) it was shown that only one kidney and its associated fat is enough to assess nutritional condition in red deer; and ii) the feasibility of using near infrared spectroscopy to predict the concentrations of stress hormone metabolites was demonstrated using faeces of red deer for the first time. Subsequently, two large-scale observational studies, conducted in representative red deer populations found in Mediterranean Iberia, highlighted the importance of considering seasonal environmental variations and variables related to hunting management practices to better understand the nutritional and physiological ecology of red deer. High population densities had adverse effects on the nutritional condition of the deer and were associated with increased stress levels in natural populations without supplementary feeding. Massive hunting events involving the use of hounds were also identified as a potential source of chronic stress in red deer. The research presented in this thesis has clear implications regarding the management and monitoring of red deer populations in Mediterranean environments and is intended to help wildlife managers to implement more effective monitoring programmes and sustainable management practices. O veado (Cervus elaphus) é, atualmente, uma das espécies de ungulados silvestres mais abundantes na Península Ibérica. É também uma espécie extremamente importante em termos ecológicos, por ser um elemento chave para o funcionamento dos ecossistemas, e socioeconómicos, por ser uma espécie de caça maior emblemática e altamente valorizada. Na Ibéria, as populações de veados estão sujeitas a diferentes práticas de gestão que podem afetar a condição física dos indivíduos de diferentes formas e, por conseguinte, determinar a sua dinâmica. Apesar da importância desta espécie, os estudos sobre os efeitos da gestão cinegética e das condições ambientais nos indicadores da sua condição física são ainda escassos nos ecossistemas mediterrânicos. Grande parte do conhecimento sobre a ecologia do veado e sobre o impacto da sua gestão cinegética é baseado em estudos realizados em regiões do norte e centro da Europa, onde as características climáticas e os sistemas de gestão diferem daqueles existentes nos ambientes mediterrânicos da Península Ibéria. Os estudos realizados a uma escala biogeográfica podem ser bastante úteis para compreender as relações das espécies com o ambiente, e podem contribuir para o desenvolvimento de práticas de gestão mais específicas e adequadas às necessidades de gestão. A otimização de procedimentos de amostragem e do uso de técnicas analíticas é também essencial para uma monitorização mais eficaz das populações silvestres em termos de tempo e custos associados e, portanto, é uma tema de grande interesse para gestores de fauna selvagem. Neste contexto, os principais objetivos desta tese foram: 1) otimizar os métodos usados para avaliar a condição física do veado; e 2) identificar os fatores de gestão cinegética e ambientais que afetam o estado nutricional e a fisiologia do stress do veado nos ecossistemas mediterrânicos da Ibéria, assim como investigar possíveis interações entre esses fatores. Dois estudos de cariz metodológico, apresentados na primeira parte desta tese, demonstraram que a condição física do veado pode ser avaliada usando procedimentos mais simples e rentáveis do que aqueles normalmente utilizados: i) demonstrou-se que o estado nutricional do veado pode ser avaliado usando apenas um rim e a sua gordura perirrenal; ii) provou-se, pela primeira vez, a viabilidade da espectroscopia no infravermelho próximo para estimar concentrações de metabólitos de hormonas de stress usando fezes de veado. Posteriormente, dois estudos observacionais, realizados em diferentes populações de veados representativas da região mediterrânica ibérica, evidenciaram a importância de considerar as variações ambientais sazonais e as variáveis de gestão cinegética para compreender a ecofisiologia e a ecologia nutricional do veado. Observou-se que as densidades populacionais elevadas afetaram de forma negativa o estado nutricional dos veados e estiveram também associadas a níveis de stress mais elevados em populações naturais sem alimentação suplementar. Para além disto, verificou-se que a realização de eventos de caça massivos com matilhas pode ser um fator de stress crónico nas populações de veados. Os resultados obtidos no âmbito desta tese têm diversas implicações no que diz respeito à monitorização e gestão das populações de veados nos ambientes mediterrânicos. Espera-se que os estudos aqui apresentados ajudem os gestores de fauna silvestre a implementar programas de monitorização populacional mais eficazes e práticas de gestão mais sustentáveis. El ciervo rojo (Cervus elaphus) es actualmente uno de los ungulados silvestres más abundantes de la Península Ibérica. Es una especie con una elevada importancia ecológica, siendo un elemento clave en la dinámica de los ecosistemas mediterráneos, y presenta un gran valor socioeconómico, al ser una especie de caza mayor emblemática y muy apreciada. En el territorio peninsular, las poblaciones de ciervos están sometidas a diferentes sistemas de manejo que pueden modular la condición física de los individuos y, consecuentemente, determinar la dinámica de sus poblaciones. Pese a la relevancia de esta especie, aun son escasos los estudios sobre los efectos de la gestión cinegética y de las condiciones ambientales en los indicadores de su condición en los ecosistemas mediterráneos. La mayor parte del conocimiento sobre la ecología de esta especie y sobre el impacto de su gestión cinegética se basa en estudios realizados en regiones del norte y centro de Europa, donde las características climáticas y sistemas de manejo son diferentes a los presentes en los ambientes mediterráneos de la Península Ibérica. Los estudios realizados a una escala biogeográfica pueden ser muy útiles para comprender las relaciones de las especies con el ambiente, y pueden contribuir al desarrollo de prácticas de manejo más especificas y adecuadas a las necesidades de gestión. La optimización de procedimientos de muestreo y la puesta a punto de técnicas analíticas son también de gran importancia para una monitorización más eficaz de las poblaciones silvestres en términos de tiempo y costes asociados y, por consiguiente, son temas de gran interés para los gestores de la fauna silvestre. En este contexto, los objetivos principales de esta tesis doctoral fueron: 1) optimizar los métodos usados para evaluar la condición física del ciervo; y 2) identificar los factores de manejo y ambientales que afectan el estado nutricional y la fisiología del estrés del ciervo en los ecosistemas de la Iberia mediterránea, así como estudiar las posibles interacciones entre dichos factores. Dos estudios con un enfoque metodológico, presentados en la primera parte de esta tesis, demostraron que la condición física del ciervo se puede valorar usando procedimientos más sencillos y rentables que los usados tradicionalmente: i) se ha demostrado que el estado nutricional del ciervo se puede evaluar usando solamente un riñón y su grasa perirrenal; y ii) se comprobó, por primera vez, la viabilidad de la espectroscopia en el infrarrojo cercano para estimar las concentraciones de metabolitos de hormonas de estrés usando heces de ciervo. Posteriormente, dos estudios observacionales basados en poblaciones de ciervo representativas de la Iberia mediterránea evidenciaron la importancia de considerar las variaciones ambientales estacionales y las variables de manejo cinegético para comprender la ecofisiología y la ecología nutricional del ciervo. Se observó que las densidades poblacionales elevadas afectan de forma negativa al estado nutricional de los ciervos y éstas se asociaron con niveles de estrés más elevados en poblaciones naturales sin suplementación alimentaria. Además, se verificó que los eventos de caza masivos con rehalas pueden representar un factor de estrés crónico en las poblaciones de ciervos. Los resultados obtenidos en esta tesis tienen implicaciones en lo que respecta a la monitorización y gestión de las poblaciones de ciervos en ambientes mediterráneos, y se espera que los estudios aquí presentados ayuden a los gestores de fauna silvestre a implementar programas de monitorización más eficaces y prácticas de gestión más sostenibles.

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Chapuis, Margot. "Mobilité des sédiments fluviaux grossiers dans les systèmes fortement anthropisés : éléments pour la gestion de la basse vallée de la Durance." Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM3019/document.

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La Durance est une large rivière méditerranéenne à charge grossière et à lit divagant. Le fonctionnement hydro-sédimentaire de son bassin versant a été profondément modifié par la mise en place d'aménagements hydro-électriques et par les extractions de graviers, qui ont entraîné une rétraction de sa bande active et une incision marquée de son lit. Ces évolutions morphologiques correspondent à des enjeux majeurs en termes de gestion du territoire en moyenne et basse Durance, du fait de la nécessité du maintien d'une capacité d'écoulement du lit en crue, et de la mobilité latérale du lit, souvent incompatible avec l'occupation de la vallée. Cette thèse, basée sur la collecte de données de terrain, vise à développer un schéma de fonctionnement du transport sédimentaire dans les rivières à charge grossière de grande largeur, en intégrant les différentes échelles spatiales (et donc temporelles). Elle a également pour objectif de donner des clefs de compréhension pour la gestion des flux sédimentaires en Durance. Les mécanismes de la mobilité des particules sédimentaires et des formes fluviales sont étudiés dans une démarche ascendante de reformulation scientifique de questionnements opérationnels The Durance River (South-Eastern France) is a large and steep wandering gravel-bed river, deeply impacted by gravel mining and flow diversion in its whole catchment area. The Durance River is characterized by a sediment deficit that led to a reduction of active channel width and river bed degradation. These lateral and vertical dynamics lead to important issues in terms of landscape management, because of (i) maintaining the bed hydraulic capacity to evacuate flood discharges and (ii) planform evolution of the river that conflicts with landscape use. This field-based thesis aims at developing a functioning scheme of bedload transport in large gravel bed rivers at various spatial (and consequently temporal) scales and gives keys to understanding for sediment fluxes management on the Durance River. Particle and bedform mobility mechanisms are studied with a scientific approach closely linked to management issues

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Dissertations / Theses on the topic 'Mediterranean streams'

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