Academic literature on the topic 'Spartina maritima'

The Spartina Schreb. genus is composed of C4 perennial grasses in the family Poaceae. They are native to the coasts of the Atlantic Ocean in western and southern Europe, north-west and southern Africa, the Americas and the southern Atlantic Ocean islands. Most species are salt tolerant and colonise coastal or inland saltmarshes. The available literature on heavy metal bioaccumulation by Spartina sp. was compiled and compared. Spartina alterniflora Loisel. and Spartina maritima (Curtis) Fernald were the most commonly researched species of the genus, whereas many species were not represented at all. In contrast, Cu and Zn are the most intensively researched heavy metals. The few studies dealing with the physiological impacts of heavy metals or the mechanisms of metal accumulation, which involve extracellular and intracellular metal chelation, precipitation, compartmentalisation and translocation in the vascular system, were documented. Bioaccumulation of metals in roots and tillers of some species of the Spartina genus (e.g. S. maritima and Spartina densiflora Brongn.) has been described as a feasible method for remediating waters and soils contaminated with heavy metals. One such example is Spartina argentinensis Parodi, which has been found to be a Cr-hyperaccumulator; it can concentrate chromium in its tissues to levels far exceeding those present in the soil.

Halophytic grasses have been recently targeted as possible sources of nutraceutical and medicinal compounds. Nonetheless, few studies have been conducted on the phytochemistry and biological activities of metabolites produced by these plants. Among these, Spartina maritima (Curtis) Fernald, Spartina patens (Aiton.) Muhl., and Puccinellia maritima (Hudson) Parl. are three halophytic grasses whose chemical composition and bioactivities are unknown. The present work broadens the knowledge on the polyphenolic and chlorophyll composition of these species identifying for the first time hydroxycinnamic acids and their derivatives, flavones, flavonols, lignans, as well as chlorophylls and xantophylls. The extracts were particularly rich in caffeic and ferulic acids as well as in trihydroxymethoxyflavone, apigenin and tricin derivatives. Interestingly, several of the identified compounds are relevant from a medicinal and nutraceutical point of view putting in evidence the potential of these species. Thus, the antioxidant, anti-acetylcholinesterase, antibacterial, and antifungal activities of the polyphenolic extracts were assessed as well as the photophysical properties of the chlorophyll-rich extracts. The results, herein presented for the first time, reinforce the nutritional and the medicinal potential of these halophytic grasses.

Os sapais são ecossistemas dinâmicos e contribuem para a defesa da linha costeira e conservação da biodiversidade. As plantas libertam exsudados na rizosfera que influenciam fortemente as comunidades de microrganismos e consequentemente a libertação de enzimas extracelulares. Estas enzimas estão envolvidas na decomposição de resíduos orgânicos e no ciclo de nutriente do solo sendo um indicador da atividade microbiana, nomeadamente da sua composição e abundância. Este estudo teve como principal objetivo a análise da atividade enzimática no rizosedimento de duas espécies de sapal, S. maritima e S. versicolor no estuário do Tejo durante 4 períodos temporais: Novembro 2012, Fevereiro 2013, Maio 2013 e Fevereiro 2014. Os resultados mostraram diferenças na atividade das enzimas fenol oxidase, β-glucosidase, fosfatase alcalina, quitobiase, sulfatase, desidrogenase (p-value < 0,05) entre espécies e entre períodos de amostragem. O pH, salinidade, matéria orgânica e humidade influenciam a atividade enzimática e os exsudados influenciam a atividade enzimática, tendo-se verificado uma separação das duas espécies; ABSTRACT: “Temporal variation of enzymatic activity associated with the microorganisms living in the Spartina maritima and Spartina versicolor rizosediment” Saltmarshes are dynamic ecosystems and contribute to defence of the coastline and biodiversity conservation. Plants release exudates that have a strong influence on the microorganisms communities present on the rhizosphere and consequently in the release of extracellular enzymes. This enzymes are involved in organic residues decomposition and nutrient cycle of the soil, being a good indicator of microbial activity, composition and abundance. The main goal of this study was the analysis of enzymatic activity of the rizosediment of two saltmarsh plant species, S. maritima and S. versicolor on Tagus estuary in four temporal periods: November 2012, February 2013, May 2013 and February 2014. The results show significant differences in phenol oxidase, β-glucosidase, acid phosphatase, alkaline phosphatase, quitobiase, sulfatase, dehydrogenase, protease and urease enzymatic activity (p-value < 0.05) between species and between sampling periods. The environmental factors such pH, salinity, organic matter and humidity also influence the enzymatic activity and exudates leading to separation by specie.

Salt marshes are coastal ecosystem in the upper intertidal zone between internal water and sea and are widely spread throughout Italy, from Friuli Venezia Giulia, in the North, to Sicily, in the South. These delicate environments are threatened by eutrophication, habitat conversion (for land reclaiming or agriculture) and climate change impacts such as sea level rise. The objectives of my thesis were to: 1) analyse the distribution and biomass of the perennial native cordgrass Spartina maritima (one of the most relevant foundation species in the low intertidal saltmarsh vegetation in the study region) at 7 sites along the Northern Adriatic coast and relate it to critical environmental parameters and 2) to carry out a nutrient manipulation experiment to detect nutrient enrichment effects on S. maritima biomass and vegetation characteristics. The survey showed significant differences among sites in biological response variables - i.e., live belowground, live aboveground biomass, above:belowground (R:S) biomass ratio, % cover, average height and stem density – which were mainly related to differences in nitrate, nitrite and phosphate contents in surface water. Preliminary results from the experiment (which is still ongoing) showed so far no significant effects of nutrient enrichment on live aboveground and belowground biomass, R:S ratio, leaf %Carbon, average height, stem density and random shoot height; however, a significantly higher (P=0.018) increase in leaf %Nitrogen content in treated plots indicated that nutrient uptake had occurred.

Salt marshes are some of the most productive ecosystems in the world and have been the centre of attention over the past few decades, due to their decline as a result of global climate change and anthropogenic impacts. The growth of salt marshes is determined by substrate type, soil conductivity and elevation. The permanently open Keurbooms Estuary along the south-east coast of South Africa is subjected to occasional fluvial flooding and its intertidal area lacks well developed salt marshes, with Spartina maritima restricted to the lower reaches of the Bitou tributary and a few sections of the Keurbooms tributary. Presumeably because of fine sediment habitat in the confluence and lower Bitou tributary. The salinity of the estuarine water ranges between 0.1 – 26.9 and 3.2 – 35.3 in the Bitou and Keurbooms tributaries respectively. A typical salt wedge salinity pattern is common in the Keurbooms tributary where saline water often intrudes underneath the freshwater, especially during high river flows. The following hypotheses were developed and tested in this study: The limited spatial distribution of S. maritima in the Keurbooms Estuary is due to limited availability of fine sediment habitat; and the source of the fine sediment in the estuary is the Bitou tributary rather than the Keurbooms tributary or the sea. It was further postulated that after sediment characteristics, floods are the major hydrological driver determining the distribution of S. maritima in the Keurbooms Estuary. The results of the surveys of the estuarine channel bottom sediments showed that the Keurbooms tributary was mostly characterized by the sand-size sediment fraction derived from the feldspathic and sandstone with evidence of fine sediment fractions restricted to the upper reaches at the confluence with Whiskey Creek. The Bitou was almost always composed of coarse sized sediments in the upper reaches, fine sediment deposits in the middle and lower reaches and medium sorted sand with almost no clay or calcium carbonate in the estuarine component below the confluence of the tributaries. These findings were further supported by the surface sediment deposited within the S. maritima intertidal salt marsh, which showed finer sediment deposits in the Bitou marsh compared to the Keurbooms marsh surface. Similar results were also found in the sediment cores, with the Keurbooms marsh sediment becoming finer with increasing depth whereas fine sediments reduced with depth in the Bitou marsh. The results of the sediment mineralogy indicated that the increased concentrations of clay minerals in the S. maritima surface sediments are derived from the Bokkeveld shale, siltstone and clay slate exposed above the N2 Bridge in the Keurbooms Estuary. GIS mapping shows that S. maritima has been declining over the past two decades, with rapid decreases especially evident after big flooding events. The GIS mapping also indicates that the patches of the S. maritima in the Keurbooms tributary are more exposed to big floods than the Bitou marsh. Despite showing an overall decline, S. maritima area coverage remained more consistent in the lower reaches of the Bitou tributary than in the Keurbooms tributary. Despite the larger and more persistent area cover, the S. maritima plants were shorter and less dense than the plants growing in the sandy substrate. The black/grey colouration of soil with increasing depth in the Bitou tributary was an indication of the reduced state of the soil caused by prolonged waterlogged conditions. The roots of S. maritima in both tributaries were mostly restricted to the sub-surface substrate layer (i.e. 0 – 0.25 m), although the Bitou populations showed more vegetative propagation than the Keurbooms populations. This mechanism of reproduction was also demonstrated during the transplant experiment which showed a greater number of new stem production in the fine sediment substrates compared to the sandy silt substrates. Although accretion rates were not determined in this study, the short-term sediment deposition rates revealed that sedimentation is active in the marshes of the Keurbooms Estuary. Therefore, in spite of showing a decline in area cover, the production of viable seed and observed vegetative propagation suggest that the S. maritima is likely to colonize open stable intertidal mudflats / sandflats, thus maintaining its distribution as an intertidal species in the salt marshes of the Keurbooms Estuary.

Tese de doutoramento, Biologia (Microbiologia), Universidade de Lisboa, Faculdade de Ciências, 2016
The major purpose of this thesis was to complement the current knowledge regarding marine fungal communities and particularly those inhabiting Portuguese temperate salt marshes. Specifically, this study mainly intended to assess the species composition and diversity of the fungal communities associated with one of the most dominant macrophytes in these ecosystems, Spartina maritima (Curtis) Fernald, and to contribute to a better understanding of community dynamics and key ecological aspects of the fungi. The study was conducted in two geographically and physically distinct salt marshes, Castro Marim and Ria de Aveiro, where 195 mature, standing live plants were collected over a 2-year period (October 2010 to August 2012) from each study site. Each air-dried plant was separated into nine substrate categories according to the vegetative structure (leaf sheaths, stems and leaf blades) and physiological state of each structure (live, senescent and decaying). Identification of marine fungi was performed by two distinct, but complementary methods, i.e. direct observation of fungal structures (fruit bodies, spores and hyphopodia) and sequencing of the internal transcribed spacer regions of rDNA (ITS). The first method involved an individual observation of each substrate under dissecting- and light microscopes for detection of fungal structures; fungal taxa were morphologically identified using specific dichotomous keys for marine fungi. The vertical position and density of fruiting structures produced by each identified fungus was also recorded. The most frequent fungi were isolated in pure cultures by single spore method. Plant materials from the same substrate category, sampling period and study site were mixed and freeze-dried. Only the plant samples from the first sampling period were used for molecular identification of fungi. This second method involved DNA extraction of pure fungal isolates and plant samples, and amplification of the ITS region. Amplicons from plant samples were cloned in order to isolate individual amplicons of mixed PCR products. ITS sequences of the 1037 clones obtained from the plant samples were submitted to a restriction fragment length polymorphism analysis (RFLP); clones with different digestion profiles were sequenced. Phylogenetic analyses were performed with sequences of clones, fungal isolates and BLAST best-hits. A comparison between morphological and molecular methods revealed a general agreement in taxonomic assignments and representativeness of each fungus in the community, vegetative structure and study site. The combination of both methods was demonstrated to be crucial for a more realistic and accurate representation of the fungal community. Forty-five fungal taxa were recorded in S. maritima samples; 91% of these were filamentous ascomycetes, included in the Dothideomycetes and Sordariomycetes. The majority of the fungal species most frequently recorded in this study were previously described from other species of Spartina. Nevertheless, the studied fungal community also included other infrequent species that represent new records for the genus Spartina and/or S. maritima plants, e.g. Anthostomella spissitecta, Camarosporium roumeguerii, Ceriporia lacerata, Coniothyrium obiones, Cryptococcus mangaliensis, Decorospora gaudefroyi, Erythrobasidium hasegawianum, Halosarpheia trullifera, Leptosphaeria marina, Penicillium chrysogenum and Stagonospora haliclysta. The presence or absence of species in fungal communities may be related with intra- and interspecific differences in the physical structure and chemical composition of the host plants and/or macro and microenvironmental factors. Similarly to other grass-like plants, the results also demonstrated that the marine fungi are vertically distributed along standing plants of S. maritima. Moreover, the most frequent fungal taxa exhibited wide vertical distribution ranges, a high investment in the production of fruiting structures and were present during all the sampling period on senescent and decaying vegetative structures. The majority of these fungi were also found on live plant tissues, which indicated that these saprobic species might initiate the colonisation of plant substrates as endophytes. These findings suggested that the vertical distribution patterns, and occurrence and ecological role of most frequent fungi depend on the phase of plant life cycle and substrate availability, micro-environmental conditions of substrates and adaptation to submersion/exposure cycles, and potential fungal competitors. During the decay process of S. maritima, the obligate marine fungi Natantispora retorquens, Byssothecium obiones and Lulworthia sp.1 seem to be involved in the complete decomposition of lower leaf sheaths and stems; facultative marine fungi Mycosphaerella sp. I, of leaf blades; facultative marine fungi Phaeosphaeria halima and Stagonospora sp. 1, of upper standing leaves; and Buergenerula spartinae and Phaeosphaeria spartinicola, of all vegetative structures.

Soil salinity has been continuously increasing and nowadays is considered a serious threat to global food security and sustainability. We argue that halophytic grasses could be the answer to this problem, since (1) they thrive under salinity environments and (2) in response to salt stress, an overproduction of some important chemical compounds is observed, from which arises the possibility of their exploitation as nutraceutics by the food, pharmaceutical, and cosmetic industries. The first step to test this hypothesis is to study their chemical profile and biological activities. Taking this into consideration, this project approaches the phytochemistry and biological activities of Spartina maritima (Curtis) Ferland, Spartina patens (Aiton.) Muhl. and Puccinellia maritima (Hudson) Parl., three halophytic grasses from Ria de Aveiro whose chemical composition and bioactivities are completely unknown. Within this work, the lipophilic and polyphenolic profile of the studied halophytic grasses were uncovered. In the first case, the hexane extracts of S. maritima and P. maritima were analyzed by GC-MS leading to the identification of 72 compounds, revealing a rich lipophilic composition. Regarding the polyphenolic profile of S. maritima, S. patens, and P. maritima, their ethanol extracts were analyzed by UHPLC-MS leading to the identification of 65 compounds. The extracts were dominated by flavones and hydroxycinnamic acids, highlighting their potential. Additionally, a clear link between overproduction of some of the identified chemical families and/or compounds and salinity stress was achieved. These compounds possess a wide range of biological activities and are associated with high nutraceutical values. Aiming to assess the bioactivities of the polyphenolic extracts of the three taxa, their antimicrobial, antioxidant and inhibition of acetylcholinesterase activities were assayed. S. patens showed the best antioxidant activity. Regarding antimicrobial activity, S. patens showed inhibition of Listeria innocua NCTC™ 11288 and P. maritima of Candida albicans NCPF 3255. At last, the polyphenolic extracts of all studied species did not show inhibition of acetylcholinesterase capacity. Moreover, aiming to optimize a suitable extraction of chlorophylls, an important family of compounds, from the three studied taxa, several extraction techniques were applied. Through the results obtained it was verified that the microwave-assisted extraction is the most suitable method for chlorophyll extraction in these plants. Furthermore, the photophysical properties of the extracts were evaluated in order to assess their potential as photosensitizers for application in photodynamic therapy. All extracts showed remarkable photostability and singlet oxygen generation. In conclusion, the results herein achieved support the hypothesis that the studied species could bring advantages in the reclaim of degraded soils for possible exploitation by pharmaceutical and food industries. Moreover, these are the first reports on the phytochemistry and biological activities of the studied species.
Atualmente, o aumento constante da salinidade dos solos constitui uma das maiores ameaças para a segurança e sustentabilidade alimentar. Uma proposta para superar esta ameaça é a utilização de gramíneas halófitas, uma vez que (1) elas prosperam sob condições de elevada salinidade e (2) apresentam uma sobreprodução de compostos químicos importantes como resposta ao stress salino, surgindo assim a possibilidade da exploração nutracêutica destas espécies pelas indústrias alimentar, farmacêutica e cosmética. O primeiro passo para confirmar esta hipótese é o estudo do seu perfil químico e das suas potenciais atividades biológicas. Por este motivo, este trabalho aborda a fitoquímica e as atividades biológicas de Spartina maritima (Curtis) Ferland, Spartina patens (Aiton.) Muhl. e Puccinellia maritima (Hudson) Parl., três halófitas gramíneas da Ria de Aveiro cuja composição química e bioatividade são completamente desconhecidas. Neste projeto, o perfil lipofílico e polifenólico das halófitas gramíneas sob estudo foram revelados. No primeiro caso, os extratos de hexano de S. maritima e P. maritima foram analisados por GC-MS, o que resultou na identificação de 72 compostos, revelando uma composição lipofílica diversificada. No segundo caso, os extratos de etanol de S. maritima, S. patens e P. maritima foram analisados por UHPLC-MS o que resultou na identificação de 65 compostos. Os extratos de etanol apresentam maioritariamente derivados de flavonoides e ácidos hidroxicinâmicos, compostos com potencial biológico relevante. De facto, estes compostos possuem uma grande gama de atividades biológicas e estão associados a elevados valores nutracêuticos. Adicionalmente, foi estabelecida uma relação clara entre algumas das famílias químicas presentes e/ou compostos identificados e o stress salino sentido pela planta. Com o objetivo de avaliar as bioatividades dos extratos polifenólicos dos três taxa sob estudo, procedeu-se à avaliação das suas atividades antimicrobiana, antioxidante e de inibição da acetilcolinesterase. S. patens demonstrou ter a melhor atividade antioxidante. Relativamente à atividade antimicrobiana, S. patens exibiu inibição de Listeria innocua NCTC™ 11288 e P. maritima de Candida albicans NCPF 3255. Por fim, os extratos polifenólicos de todas as espécies não apresentam capacidade de inibição da acetilcolinesterase. Com o intuito de potenciar a valorização dos três taxa sob estudo, procedeuse à otimização do processo de extração das clorofilas presentes, através da variação das técnicas de extração empregues. Da análise dos resultados obtidos, a extração assistida por micro-ondas revelou-se o método mais adequado para a extração de clorofilas a partir destas plantas. Para além disso, o potencial dos extratos clorofílicos para atuarem como fotossensibilizadores foi avaliado através do estudo das suas propriedades fotofísicas. Todos os extratos demonstraram fotoestabilidade e capacidade de geração de oxigénio singleto. Em suma, os resultados obtidos suportam a hipótese da utilização destas espécies na reivindicação dos solos degradados para possível exploração pelas indústrias farmacêutica e alimentar. Para além disso, este é o primeiro relato da fitoquímica e atividade biológica destas espécies.
Mestrado em Bioquímica

Eutrophication, particularly due to nitrogen (N) and phosphorus (P) input, has been massively altered by anthropogenic activities. Thus it is important to understand the impact on salt marsh plants; however studies on salt marsh plants within Galveston Bay, Texas are limited. In this study, the effects of repeated nutrient additions in monospecific plots of Spartina alterniflora, Batis maritima¸ and Salicornia virginica as well as mixed plots of B. maritima and S. virginica were studied over 15 months. Results showed that nutrient loading led to an increase in height, biomass, growth rate and percent nitrogen (N) within all three species studied, but were species specific more than dose dependent. Nitrogen content in leaves had a positive correlation with P content in leaves but a negative correlation with carbon (C) content. Nutrient loading lead to a significant increase in total chlorophyll in the fertilized plots of S. alterniflora and S. virginica one month into the study. Nutrient addition to two succulent species, B. maritima and S. virginica in mixed plots did not reveal a distinct superior competitor within the 15 month study in terms of growth and nutrient use efficiencies; however using the maximum growth rates of the monospecific plots, the Monod model was used to determine which species would dominate at high nutrient loads. Based on height data S. alterniflora would dominate, while B. maritima would dominate according to the Monod model based on biomass.

Dissertação de mestrado, Biologia Marinha, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2015
Carbon sinks are natural or artificial reservoirs in which carbon can be accumulated for a certain length of time. Mangroves, salt marshes and seagrasses beds are habitats that have an important role on the carbon budget of the oceans and thus influence the oceanic cycle. In this study we aimed is to evaluate C storage capacity of two different intertidal environments, Zostera noltii vs Spartina maritima from Ria Formosa, as well as to evaluate the influence of hydrodynamics and sediment grain size in the C storage. This multidisciplinary and integrated approach includes biological, geological and chemical analyses in order to better understand the processes leading to Carbon accumulation in sediments. For such a purpose, we analyzed and measured the granulometry, color and mineral composition of the sediment, as well as the organic matter, calcium carbonate contents and the elemental composition. The results obtained reflect that the carbon sequestration (organic carbon content), is related to practically all the studied variables, Furthermore, there are significant differences between both biological communities. Spartina maritima shows nearly twice the organic carbon content than Zostera noltii. On the other hand, the distance to the main navigation channel, a proxy to hydrodynamics, affected all parameters, strongly affected C accumulation, with higher variability in Zostera than Spartina. C accumulation and sediment grain size were related to this gradient, as expected, where both parameters increased from the first station, close to the main channel, to last station the most remote. The carbon accumulation rate for Spartina environment was twice as high as those for Zostera environment, 131.8 g OC.m-2.year-1, 83.9 g OC.m-2.year-1, respectively, these differences were related to the influence to all the parameters analyzed in this study.
Os sumidouros de carbono são reservatórios naturais ou artificiais, nos quais o carbono pode ser acumulado durante um determinado período de tempo. Mangais, sapais, salinas e pradarias marinhas são habitats que têm um papel importante no balanço de carbono dos oceanos e, assim, influenciam o ciclo oceânico. Eles representam um hotspot mundial para armazenamento de carbono orgânico (OC). Estes habitats compartilham uma parcela excessiva no sequestro de C em relação aos habitats terrestres. Este OC pode ser encontrado na biomassa viva especialmente enterrada nos sedimentos. A acumulação de OC em sedimentos marinhos fornece armazenamento de C a longo prazo. Esta acumulação OC é influenciada por alguns parâmetros ambientais, tais como, por exemplo, a distância ao continente e/ou o tamanho de grão e pH, assim como o tipo de ambientes de marés. Devido à falta de dados de deposição de carbono na área de estudo e também para destacar a importância destes ecossistemas no sequestro de carbono, neste estudo pretendeu-se avaliar "sumidouros de C" em relação a estes parâmetros ambientais tais como, por exemplo, a hidrodinâmica marinha relativamente à distancia ao continente, ou o sedimento, relativamente ao tamanho do grão nas diferentes estações de amostragem. Adicionalmente, dois diferentes ecossistemas intertidais da Ria Formosa, Zostera noltii vs Spartina marítima, foram avaliados. Esta abordagem multidisciplinar e integrada inclui análises biológicas, geológicas e químicas, para melhor compreender os processos que conduzem à acumulação de carbono, conservação ou degradação. Para tal, foi realizada uma amostragem ao longo de um canal principal e um canal secundário da Ria Formosa, em quatro estações diferentes, sendo que em cada estação os dois ecossistemas foram amostrados. No laboratório, analisámos as características sedimentológicas, onde foi determinado o tamanho das partículas por difração laser e por uso de peneiros, com o obejctivo de estimar o nível relativo de energia presente no ambiente onde o sedimento foi transportado e depositado. A cor dos sedimentos foi analisada em todo o espectro de luz visível por reflectância difusa, permitindo-nos adquirir uma aproximação da composição do sedimento. Também foi estudada a composição mineralógica por difração de raios-X. Por outro lado, foram analisadas as características geoquímicas, o que incluiu a determinação da matéria orgânica e carbonato perdidos por combustão, análise de composição elementar (OC, IC, IN e ON) através de um sistema de combustão elementar e o raio de C/N foi calculado, para ter uma ideia aproximada da origem ou fonte da matéria orgânica. Também foi determinada a concentração de pigmentos, onde por um lado foram analisadas as concentrações de clorofila e carotenóides, usando uma extração simples com acetona e medidas as concentrações através do espectrofotómetro. Seguidamente, através de cromatografia HPLC, foram analisados os pigmentos específicos. Os resultados destas últimas análises foram, no entanto, não representativos, uma vez que os valores obtidos apresentavam artefactos de degradação, não tendo sido considerados. O processamento de dados foi realizado utilizando o software estatístico R. Todas as propriedades físicas e bioquímicas de sedimentos foram avaliadas para cada estação e para cada tipo de habitat, avaliando a sua variabilidade. Um estudo ANOVA de dois fatores, sendo um de eles ‘estação’ e o outro ‘tipo de comunidade biológica’, foi aplicado a cada variável, de modo a saber se houve ou não diferenças significativas dependentes de cada fator individualmente ou devido ao efeito da interferência de ambos. Nos casos em que se verificaram diferenças, foi usado um post-hoc para determinar a origem da diferença, neste caso usamos o teste de Tukey. O software Gradistat, foi utilizado para calcular o cálculo estatístico do tamanho de grão. Nos resultados em relação às características sedimentológicas, o tamanho da partícula reflete um gradiente em que o tamanho do grão nas amostras diminui à medida que nos afastamos do canal principal e nos aproximamos das estações do canal secundário. Este gradiente é mais marcado no caso da Zostera do que no da Spartina. Esta diferença na intensidade do gradiente entre ambos ambientes pode ser devido às diferenças de hidrodinamismo entre os dois meios, uma vez que a Zostera está mais exposta que a Spartina devido à sua posição no intertidal Relativamente aos resultados de cor, foi observada a possível presença de várias formas de Fe e goetita devido aos tons do sedimento, apresentando um aumento em ambos os valores ou aumentado o conteúdo dessas substâncias da estação 1 para a 4 para ambos os ambientes. No composição mineral verificaram-se diferenças entre o teor de quartzo e polissilicatos entre as estações, aumentando o conteúdo de polissilicatos e redução do teor de quartzo nas estações mais protegidas. Também a presença de pirita e siderita poderia explicar os altos valores de matéria orgânica, ao proporcionar um possível ambiente redutor. Um grande conteúdo em carbonatos foi encontrado na estação 4, podendo explicarse devido à possível presença de foraminíferos. Em relação ao sequestro dos carbonos, é influenciado por praticamente todas as variáveis estudadas, já que influenciam as características do solo, favorecendo ou desfavorecendo a acumulação de carbono. Como por exemplo a presença de determinados compostos minerais ou substâncias que foram determinadas na análise da composição mineral e cor, que favorecem a agregação de matéria orgânica, ou outras resultando em condições reduzidas permitindo que ocorra uma maior acumulação no sedimento. Nem todas as variáveis mostram o mesmo padrão ou tendência relativamente às estações ou ao tipo de comunidade biológica. Para todas as variáveis estudadas neste trabalho, apenas algumas delas não apresentaram variações em ambos os fatores estudados. A melhoria destas representam diferenças entre estação e entre ambientes e mais da metade respondem à interação deles. Atendendo ao objetivo principal deste estudo, foram encontradas diferenças significativas entre os dois ambientes, mostrando a Spartina aproximadamente o dobro do conteúdo de carbono do que a Zostera. Esta variabilidade foi relacionada com o tamanho do grão, observando-se uma relação positiva entre a concentração de carbono orgânico e a presença de sedimentos mais finos. Todos os fatores encontram-se influenciados pela composição do solo e hidrodinâmica. Finalmente, quando foi calculada a taxa da acumulação do carbono, Spartina acumula dobro do que a Zostera, com resultais de valores de 131.8 g OC.m-2.year-1, 83.9 g OC.m- 2.year-1, respectivamente. Estas diferenças foram relatadas pela influência de todas os parâmetros analisados em este estudo.

This chapter recalls the series of events which led to the breakup of the Athenian–Spartan alliance. It begins with an earthquake and the rebellion of Sparta's helots (slaves), for which the Spartans had appealed to their allies—among them the Athenians—for help. After all, the friendship between the two powers had made possible the Hellenic victory in the Persian Wars and opened the way for the emergence of Athens' maritime hegemony in the aftermath. However, circumstances had changed dramatically as a consequence of these devastating events. At least for the time being, Athens no longer needed Sparta's forbearance. Moreover, as a consequence of the promise that the Lacedaemonians had made to the Thasians and of the breach with Sparta that the Athenians had initiated in the aftermath of Cimon's return from Messenia, a great strategic rivalry soon began, and, as everyone understood, active warfare would ensue not long after.

This concluding chapter discusses the agreement conducted between the Athenian diplomat Callias and the Spartans during the 440s. The resulting arrangement reflected an enduring balance of power. It acknowledged the facts and left the Spartans and their allies supreme on land and the Athenians supreme at sea. In the aftermath, neither was in a position to strike terror into the other. The Peloponnesus was once again a bastion of defense for Lacedaemon, and Athens retained her Long Walls, her maritime allies, and her great fleet. Furthermore, neither Sparta nor Athens nursed a grievance. Apart from Aegina and Naupactus and perhaps Molycreium to the north of the Corinthian Gulf and Chalcis to the west on the north shore of the Gulf of Patras, Athens relinquished everything that she had seized. None of her remaining acquisitions lay within Lacedaemon's natural sphere of influence; and, to head off possible objections on the part of the Spartans, she may even have reiterated that she would honor the autonomy of their sometime allies the Aeginetans.

The concept of cross-domain deterrence can shed new light on one of the most famous wars in the history of international relations. In ancient Greece, Athens enjoyed unquestioned maritime superiority, and Sparta was the dominant land power. Both sides played to their competitive advantage, but they failed to prevent a war. Yet while cross-domain deterrence failed when both sides wanted it to succeed, it also succeeded when both sides wanted it to fail. Neither side was able to engineer a decisive confrontation in its preferred domain that might have forced the other to capitulate, which resulted in a costly, protracted war. This novel interpretation of a classic case challenges popular characterizations of cross-domain strategic dynamics as rapid and unstable; they can also be slow and stabilizing. Similar cross-domain disparities two millennia later in Asia, for example, have the potential to make any conflict between China and the United States longer, more costly, and less decisive than either side perhaps expects.