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Lu, Songhui. "Ecological studies of phytoplankton and harmful algal blooms in Junk Bay, Hong Kong." Click to view the E-thesis via HKUTO, 2001. http://sunzi.lib.hku.hk/hkuto/record/B42576209.
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Dilmahamod, Ahmad Fehmi. "The biophysical processes controlling the South-east Madagascar Phytoplankton Bloom." Thesis, Brest, 2018. http://www.theses.fr/2018BRES0022/document.
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A partir d'un ensemble de données d'observation ainsi qu'un modèle couplé physiquebiogéochimique à haute résolution (CROCO-PISCES), cette thèse explore les processus biophysiques associés à l’une des plus grandes floraisons phytoplanctoniques de l’océan global, au Sud-Est de Madagascar, et le possible rôle des tourbillons sur ces blooms. L’étude montre que ce phénomène se produit dans une région caractérisée par une couche de mélange peu profonde, avec des eaux de surface moins salées probablement associées au courant Sud-Est de Madagascar (SEMC), et avec une structure dipolaire dans la circulation moyenne. Les observations ont révélé une diminution des remontées d’eaux froides (upwelling) le long des côtes sud-est de Madagascar pendant les mois de bloom. Dans le modèle, les nitrates provenant des niveaux de subsurface (advection verticale ; upwelling) ainsi que de la côte malgache (advection horizontale) favorisent la production phytoplanctonique simulée. Une expérience lagrangienne de particules montre une plus forte advection de ces dernières dans la zone de floraison pendant les périodes de bloom alors qu’elles sont déviées vers le sud de Madagascar vers le continent Africain pendant les années sans floraison. Une étude est réalisée à partir d’un jeu de données de suivi des tourbillons co-localisés avec des flotteurs de profilage Argo, pour mieux comprendre des tourbillons intensifiés en surface et subsurface. Une méthode d’identification des structures tourbillonnaires de subsurface a été mise en place en se basant sur l’anomalie de la hauteur dynamique stérique. Ces tourbillons, appelés ‘SIDDIES’ (South Indian ocean eDDIES), se produisent en tant que tourbillon intensifié en surface (surfSIDDIES) et en subsurface (subSIDDIES). Ils se déplacent le long d’une bande de latitude située entre 15°S et 35°S appelée « couloir SIDDIES ». Au cours de leurs déplacements, les subSIDDIES cycloniques (anticycloniques) transportent via les processus d’advection, des masses d’eaux chaudes et peu salées de l’Est vers l’Ouest de l’Océan Indien, contribuant ainsi à environ 58% (32%) du flux total de chaleur par tourbillons dans le sud de l'océan IndienUsing observational datasets and a high resolution coupled biophysical model (CROCOPISCES), the main aims of this thesis is to study the biophysical processes associated with one of the largest phytoplankton blooms in global ocean, southeast of Madagascar, and the possible role of mesoscale eddies.The study has shown that the bloom occurs in a region of shallow-stratified mixed layer water, with low-salinity waters at the surface possibly associated with the South-East Madagasacar Current (SEMC), and dipole structure in the mean circulation. Observations show that curren-driven upwelling south of Madagascar is reduced during bloom months. It is shown in the model that nitrate from subsurface levels (upwelling) as well as from the Madagascan coast (advection) fertilize the simulated bloom. A Lagrangian analysis shows dispersion of higher percentages of particles in the bloom region during bloom years and south of Madagascar during non-bloom years.Using co-located Argo profiles and an eddy detected algorithm dataset, surface and subsurface-intensified eddies are studied. Subsurface eddies are identified using a detection method based on their steric dynamic height anomaly. Referred to as `SIDDIES’ (South Indian ocean eDDIES), they occur as surface (surfSIDDIES) or subsurface (subSIDDIES) and propagate along a latitudinal band (15°S-35°S) termed as `SIDDIES Corridor’. Advecting warm and fresh water during their propagation, cyclonic (anticyclonic) subSIDDIES contribute about 58% (32%) of the total eddy-heat flux in the South Indian Ocean
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Härnström, Karolina. "Bloom dynamics and population genetics of marine phytoplankton : community, species and population aspects /." Göteborg : Department of Marine Ecology, University of Gothenburg, 2009. http://gupea.ub.gu.se/dspace/bitstream/2077/20913/1/gupea_2077_20913_1.pdf.
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Ebert, Kerstin [Verfasser]. "Exceptional phytoplankton bloom recognition from visible spectral satellite radiometry data / Kerstin Ebert." Berlin : Freie Universität Berlin, 2009. http://d-nb.info/1023750376/34.
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Hemmings, John Christopher Paul. "Quantitative modelling of spatial variability in the north Atlantic spring phytoplankton bloom." Thesis, University of Southampton, 1999. https://eprints.soton.ac.uk/42095/.
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The effects of variability in the physical environment on the development of the spring phytoplankton bloom are investigated using a physically forced model of the annual plankton cycle in the ocean mixed layer. The model is optimised to fit survey data from the eastern North Atlantic, collected over a 1500 x 1500 km area between 39N and 54N, from April-June 1991, establishing the feasibility of using spatially distributed point-in-time data in model calibration. Measurements made below the seasonal pycnocline show the existence of an empirical relationship between preformed nitrate and salinity in this area, allowing salinity-based estimates of pre-bloom mixed layer nitrate concentration to be made. These estimates provide important additional constraints for the model. The observed spatio-temporal patterns, at scales between 36 km and 1500 km, in nutrients, chlorophyll and measures of bloom progression derived from these data with reference to pre-bloom nitrate are discussed, together with the corresponding patterns in seasonal stratification. During the spring bloom, when biogeochemical concentrations vary rapidly in response to the developing stratification, absence of data defining its history limits the value of comparison between point-in-time observations and model results. Predictions of variation in stratification at the seasonal time-scale from general circulation models (GCMs) can be used in place of observational data to force ecosystem models. However, the degree to which observations are used to constrain the model solutions should allow for both model error in stratification and misrepresentation of the seasonal development of stratification by the observations. The latter occurs due to sampling error associated with short-term fluctuations. It can be corrected for if a suitable contemporary sea surface temperature data set is available to define the variation of mixed layer temperature at the seasonal time-scale. It is shown that the accuracy of the GCM predictions can be improved by the application of meteorology specific to the year of observation. It is also shown that the sensitivity of the ecosystem model predictions to error in the physical forcing can be reduced by matching model and observations by a stratification measure, rather than by time, when comparing fields. The survey data show an important contribution to the stratification arising from the 'tilting' action of vertical shear on pre-existing horizontal buoyancy gradients in the winter¬ time mixed layer. This effect was severely underestimated by the GCM. The discrepancy can be accounted for by the absence of density fronts and mesoscale dynamics in the model. Ecosystem model results suggest that spatial variance in Zooplankton grazing, due to the effect of differences in the depth and duration of winter-time mixing on the over-wintering success of plankton populations, is one of the major factors controlling the spatial and temporal characteristics of the phytoplankton bloom.
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Matlakala, Mmakabele Lebogang. "Seasonal characteristics of phytoplankton bloom phenology in the northern Benguela Upwelling System." Master's thesis, Faculty of Science, 2019. http://hdl.handle.net/11427/31598.
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Seasonal phytoplankton blooms in the Benguela Upwelling System (BUS) play a crucial role in ecosystem services and driving climate change through air-sea gas exchanges. Upwelling systems are particularly are sensitive to effects of climate change including the transport of nutrients, which influence the composition of phytoplankton communities. This is important because species composition affects a number of key processes that have significant climate feedbacks. This study uses historical long-term in situ data (at 10 and 70 NM stations) as well as OC-CCI satellite ocean colour data to investigate seasonal phytoplankton bloom phenology and community structure of diatoms, dinoflagellates and coccolithophores in the northern BUS. The seasonal cycle of satellite chlorophyll was used to determine the timing of bloom initiation at inshore and offshore boxes that overlapped the in situ stations. An ocean colour algorithm to detect coccolithophore presence and absence was used to determine the inshore-offshore seasonal cycle of coccolithophores. Results indicate a gradual decrease in chlorophyll concentration further offshore as well as high intra-seasonal, inter-annual and spatial variability. Offshore blooms initiate later and last longer than inshore blooms which have a higher magnitude. Diatoms are dominant over dinoflagellates and coccolithophores throughout the northern BUS, with higher concentrations observed at the inshore station (10 NM) for all three phytoplankton groups. However, satellite results show a higher presence of coccolithophores in the offshore region during spring and summer that is associated with periods of strong stratification. This study provides a better understanding of the characteristics of the phytoplankton seasonal cycle in the northern BUS which is useful for detecting trends and possible change associated with climate change forcing in response to global warming.
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Lu, Songhui, and 呂頌輝. "Ecological studies of phytoplankton and harmful algal blooms in Junk Bay, Hong Kong." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B42576209.
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Mahadik, Gauri A. "The role of copepod grazing in phytoplankton bloom dynamics : a species-based approach." Thesis, Open University, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.664472.
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Seasonal phytoplankton blooms characterize the pelagic communities in temperate oceans and in coastal regions of the Mediterranean Sea. The present study was aimed at understanding the role of trophic interactions in the dynamics ofphytoplankton blooms in a long-term time series in the inner Gulf of Naples (LTER-MC) where phytoplankton and mesozooplankton are dominated by diatoms and copepods, respectively. The abundant calanoids Acartia clausi, Centropages typicus, Paracalanus parvus, and Temora styli/era peak in different seasons and interact with different co-occurring phytoplankton communities, of which the diatoms Chaetoceros socialis, Leptocylindrus spp. and Pseudonitzschia spp. are the most abundant. By following a species-specific approach, the feeding performances and behaviour of the four copepod species on selected bloom-forming diatoms were analyzed by incubation experiments using the food removal method and video recordings of individuals at small scale. Significant differences appeared in the feeding responses of the copepods to the different diatom species, which can be attributed to the species-specific traits of both the predator and prey. Copepods showed behavioral plasticity in presence of different diets, with changes in the duration of feeding bouts and proportion of time allotted to different behaviors, which can in turn affect the feeding rates. Finally, the estimated impact of copepod grazing at st. LTER-MC showed that the copepods can remove a significant portion ofthe bloom-forming diatoms but have a limited impact on total standing stock of a diversified diatom assemblage. The impact also varies depending on the phases of the blooms with respect to the abl;lndance and composition of the plankton communities. This study discloses the role of key copepod species in the dynamics ofphytoplankton blooms for a better understanding of the seasonal and long-term patterns of plankton communities in marine coastal ecosystems.
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Garcia, Virginia Maria Tavano. "The effect of irradiance on production and growth of the bloom-forming dinoflagellate Gyrodinium aureolum." Thesis, University of Southampton, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.330113.
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Jephcott, Thomas. "Profiling an invader - is the invasive cyanobacterium Raphidiopsis raciborskii on the path to ecological dominance in Australia in the context of environmental change?" Thesis, The University of Sydney, 2018. http://hdl.handle.net/2123/20681.
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Biological invasions are commonly reported ecological phenomena and are universally accepted as symptoms of the Anthropocene. Microbial invaders are particularly difficult to study, but potentially represent the most serious group of invaders, due to their extremely rapid responses to changing conditions. In this group, phytoplankton are perhaps the most significant; they are responsible for most of the primary production in aquatic ecosystems and are therefore the cornerstone of aquatic food webs. However, they can also produce toxins that pose threats to water quality, particularly when they form extensive blooms. One species exhibiting invasive behaviour is Raphidiopsis raciborskii. Known for its production of potentially lethal toxins, and flexible physiology, it favours warming temperatures and stratification regimes. In Australia, these conditions are becoming more prevalent, and with the species already having a foothold in many Australian ecosystems, it may continue to spread and impact ecosystem servies and stability. In this thesis, we use a combination of historical, theoretical, laboratory, and monitoring data studies to examine the factors behind the success of R. raciborskii in the context of Australian ecosystems. This research provides novel contributions to the field by demonstrating that ‘invasiveness’ is a symptom linked to environmental change, that R. raciborskii exhibits metabolic plasticity under various conditions, that R. raciborskii may be implicated in changing the bacterial community structures of freshwater systems, and that the historic presence of R. raciborskii in Australian environments reinforces its theoretically and experimentally purported environmental niche. This knowledge facilitates discussion of Australian water security and ecological health, and the critical importance of phytoplankton communities, in the face of an increasing population and cascading environmental change.
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Lawson, Gabriella Marie. "Seasonal Nutrient Limitations of Cyanobacteria, Phytoplankton, and Cyanotoxins in Utah Lake." BYU ScholarsArchive, 2021. https://scholarsarchive.byu.edu/etd/9183.
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Excess nutrients from human activity trigger toxic cyanobacterial and algal blooms, creating expansive hypoxic dead zones in lakes, damaging ecosystems, hurting local economies, undermining food and water security, and directly harming human health. To identify when and where nutrients limit phytoplankton and cyanobacterial growth, and cyanotoxin concentrations across Utah Lake, USA we conducted four in-situ bioassay studies (563 cubitainers or experimental units) that experimentally added N, P or N+P over the spring, early summer, summer, late summer, and fall in lake water from the top 20 cm of the water column. For our purpose, we defined total phytoplankton as all prokaryotic or eukaryotic organisms containing chlorophyll-a. We evaluated changes in chlorophyll-a and phycocyanin concentrations; the abundance of cyanobacterial species and total phytoplankton species or divisions; cyanotoxin concentrations of the microcystin, anatoxin-a, and cylindrospermopsin; DIN, SRP, TP, and TN concentrations; and other water chemistry parameters. We found that the nutrient limitation of cyanobacteria, and to a lesser extent phytoplankton, was influenced by season and space. Cyanobacteria were often co-limited in the spring or early summer, limited by a single nutrient in the summer, and not limited by N or P in the late summer and fall. Alternatively, phytoplankton were co-limited from the summer into the fall in the main body of the lake and either N limited or co-limited continually in Provo Bay. Microcystis, Aphanocapsa, Dolichospermum, Merismopedia, and Aphanizomenon spp., and Aulacoseira and Desmodesmus spp. and two taxonomical categories of algae (i.e., unicellular and colonial green algae) were primarily associated with cyanobacteria and phytoplankton nutrient limitations. Concentrations of the three cyanotoxins demonstrated a seasonal signal and loosely followed the growth of specific cyanobacteria but was not dependent on total cyanobacterial cell density. The DIN and SRP were biologically available in all water and nutrient treatments with nutrient concentrations declining over the incubation period, suggesting that nutrient levels were not oversaturated. Our results offer insights into specific nutrient targets, species, and, and cyanotoxins to consider in the future to manage Utah Lake.
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Amnebrink, Dennis. "Transcriptomic profiling of marine bacteria between development and senescence phases of a phytoplankton bloom." Thesis, Linnéuniversitetet, Institutionen för biologi och miljö (BOM), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-79200.
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Bacterioplankton provide important ecosystem functions by carrying out biogeochemical cycling of organic matter. Playing an important role in the microbial loop they help remineralize carbon and nutrients. Bacteria also interact with phytoplankton during phytoplankton blooms. However, fundamental understanding on the underlying molecular mechanisms involved in the degradation of phytoplankton-derived organic matter is still in its infancy. Therefore, we analysed data from a mesocosm experiment following a natural phytoplankton-bloom from an upwelling system in the North- East Atlantic Ocean. The purpose was to contribute a mechanistic understanding based on functional gene expression analysis of natural microbial assemblages. Our results show the difference in functional gene expression within a bacterial metacommunity and how this functional response drastically switches between bloom build up and senescence. Transcripts showed a broad change in gene expression involving major SEED categories, with the bloom senescence phase exhibiting a higher relative abundance in major categories such as Carbohydrates, Protein Metabolism and Amino Acids and Derivatives. Within these categories genes connected to carbon utilization and transport systems (Ton and Tol) as well as chemotaxis showed a higher abundance during bloom senescence. The change in functionality based on transcripts showed a different bacterial community composition appearing over a very short time. We thus conclude that the bacterial functional gene expression response between build-up and degradation bloom phases is remarkably different and associated with a change in the identity of bacteria with active expression. Our findings highlight the importance of bacterial substrate specialists with different functional roles during different time points of phytoplankton blooms.
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Saeck, Emily A. "Nutrient Dynamics of Coastal Phytoplankton: The Role of Episodic Flow Events and Chronic Sewage Discharges." Thesis, Griffith University, 2012. http://hdl.handle.net/10072/367866.
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Nutrient enrichment of coastal zones can lead to longer phytoplankton bloom seasons, shifts in phytoplankton community composition and a higher frequency of harmful algal bloom events (HABs). Predicting the effect of nutrient enrichment on any given coastal system is challenging, as the response is mediated by the physical and biological characteristics of the system and the way in which nutrients are delivered to the system. For example, in tropical and sub-tropical regions, the majority of annual
nutrient loads are delivered via episodic high-flow events during the wet season. These events stimulate phytoplankton growth and are known to represent an important driver of coastal productivity. However, in populated coastal settings other nutrient inputs from point sources, such as sewage treatment plants (STP), are typically delivered as a relatively constant discharge. While chronic STP nutrient loading may be relatively low compared to flow event inputs, their continuous delivery throughout
the year may represent a significant source of nutrients for phytoplankton growth, particularly during the dry seasons. These different sources of nutrients, and the spatial and temporal characteristics of their delivery to receiving waters, likely influence the responses of phytoplankton communities.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Science, Environment, Engineering and Technology
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Ali, Elham Mahmoud. "Processes and conditions influencing phytoplankton growth and bloom iniation in a macrotidal estuary, Southampton Water." Thesis, University of Southampton, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274569.
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Chan, Terence. "Phytoplankton dynamics in a seasonal estuary." University of Western Australia. Centre for Water Research, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0089.
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[Truncated abstract] The Swan River is a highly seasonal estuary in the south-west of Western Australia. Salinity may vary from fresh to marine at various times throughout the estuary, depending mostly on the intensity of freshwater discharge. There are occasional problematic dinoflagellate blooms which have spurred investigation of the dynamics of the phytoplankton community. The objective of this research was to examine how phytoplankton biomass and species' successions are influenced by the multiple variables in the aquatic ecosystem, and, if possible, to determine the dominant factors ... Comparisons of phytoplankton nutrient limitation simulations with experimental observations from field bioassays require further investigation, but reinforce findings that nutrients may only limit phytoplankton biomass when there is a convergence of favourable hydrological and hydrodynamic conditions. The Swan River estuary has undergone substantial hydrological modifications from pre-European settlement. Land clearing has increased freshwater discharge up to 5- fold, while weirs and reservoirs for water supply have mitigated this increase and reduced the duration of discharge to the estuary. Nutrient loads have increased approximately 20-fold from pre-European levels. The individual and collective impacts of these hydrological changes on the Swan River estuary were examined using the hydrodynamic-ecological numerical model. The simulation results indicate that despite increased hydraulic flushing and reduced residence times, increases in nutrient loads are the dominant perturbation, producing increases in the frequency and biomass of blooms by both estuarine and freshwater phytoplankton. By comparison, changes in salinity associated with altered seasonal freshwater discharge have a limited impact on phytoplankton dynamics. Reductions of nutrient inputs into the Swan River estuary from its catchment will provide a long-term improvement in water quality but manipulations of freshwater discharge have the potential to provide a provisional short-term remediation measure allowing at least partial control of phytoplankton bloom potential and eutrophication.
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Wolfe, Megan Amelia. "Impact of wind and river flow on the timing of the Rivers Inlet spring phytoplankton bloom." Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/27081.
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The primary objective of this masters study is to develop an understanding of the physical processes driving the timing of the spring phytoplankton bloom in Rivers Inlet. The spring bloom is initiated as light limitation is lifted causing an increase in growth which overcomes loses due to grazing and advection. The bloom is terminated by nitrate exhaustion. The physical system can impact the spring bloom through variations of winds, cloud coverage, and river input. Strong winds showed two effects. First, strong winds increased the mixing layer depth which decreased the amount of light available for phytoplankton, thus delaying the timing of the spring bloom. Second, large outflow winds caused flushing events to occur resulting in rapid horizontal advection removing the plankton population from the area. River discharge has two opposite effects on the timing of the spring bloom. High river discharge causes the water column to stratify, reducing the mixing layer depth which provides more light available for growth and results in an earlier bloom. High discharge will also result in higher upwelling advection leading to a larger advective loss term for phytoplankton, delaying the bloom. Changes in cloud coverage will directly affect the incoming solar radiation and the light available for photosynthesis.
A coupled bio-physical model is used to explore the driving forces involved in the timing of the spring phytoplankton bloom in Rivers Inlet, British Columbia, Canada.
The primary control on the timing of the spring bloom in Rivers Inlet is wind speed and direction. Secondary control on the timing is due to freshwater flow; high river discharge delays the bloom in Rivers Inlet. Single outflow wind events can result in a 7 day delay in the bloom timing. The shift in bloom timing resulting from multiple outflow wind events is greater than the sum of the individual wind events. Implications of flushing events in fjords along the British Columbia coastline are also discussed.
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Bárbulo, Diego. "Influence of sea ice seeding on the spring phytoplankton bloom : An experimental study in the Gulf of Bothnia." Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-148586.
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The influence of sea ice seeding on the northern Baltic Sea´s pelagic phytoplankton spring bloom was studied in a laboratory experiment in which microcosms mimicked sea conditions. On March 26th, 2018, samples (ice cores and seawater) were taken from land-fast ice at a coastal station in the Gulf of Bothnia. The seeding experiment lasted for 9 days, during which a 12:12 hours light:dark incubation took place. Four different treatments (two with ice and two without it) were set up in twelve incubated microcosms. Samples for analyses were taken on days 0, 3, 6 and 9. On day 0, measurements were carried out on four melted ice cores and on seawater. On the remaining days analyses were performed on the incubated microcosms. The measured variables were: chlorophyll a, phytoplankton abundance, bacterial abundance, conductivity and nutrients (TDN and TDP). The most abundant algal species were identified in a qualitative analysis. The obtained data were processed to calculate the average and standard deviations and to assess the existence of statistically significant differences among the treatments. A significant increase in chlorophyll a, phytoplankton and heterotrophic bacteria abundances was detected. A parallel decline in the nutrient concentrations was observed. A relationship between phytoplankton´s degree of influence and cell-size is suggested: cells > 3µm were more abundant in ice than in seawater, and the opposite tendency was appreciated for cells < 3 µm. My study shows that sea ice seeding can have a marked seeding effect on the size structure of the spring phytoplankton bloom.
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Schock, Kevin A. "An analysis of a persistent isotherm tilt during early-spring and its effect on the diatom bloom : Lake Washington, Seattle, WA /." Thesis, Connect to this title online; UW restricted, 2008. http://hdl.handle.net/1773/10177.
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Frame, Elizabeth R. "Mycosporine-like amino acids (MAAs) in bloom-forming phytoplankton : the influence of nitrogen, ultraviolet radiation and species composition /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2004. http://wwwlib.umi.com/cr/ucsd/fullcit?p3144314.
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Zhu, Zhi. "Monitoring the Phytoplankton Community Response to Recent Geoengineering Initiatives at Grand Lake St. Marys." Bowling Green State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1343415539.
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Labiosa, Rochelle Grover. "Phytoplankton bloom formation in oligotrophic regions : the interplay between ecology and physics in the gulf of Aqaba red sea /." May be available electronically:, 2007. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Luengen, Allison Christine. "Investigating the spring bloom in San Francisco Bay : links between water chemistry, metal cycling, mercury speciation, and phytoplankton community composition /." Diss., Digital Dissertations Database. Restricted to UC campuses, 2007. http://uclibs.org/PID/11984.
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Rousso, Benny Z. "Optimization of cyanobacteria bloom management through improved forecasting models and optical sensors." Thesis, Griffith University, 2022. http://hdl.handle.net/10072/412995.
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Cyanobacteria are a diverse group of microorganisms adapted to a range of environmental conditions that favour their ubiquity in waterbodies. Cyanobacteria harmful blooms (CyanoHABs) are events in which a cyanobacteria population grows rapidly, dominates the phytoplankton community and may release toxins or other noxious compounds in the waterbody. The frequency and magnitude of CyanoHABs are increasing as a result of climate change and increased pollution from urbanisation and agriculture expansion, representing a major risk to the public health and economy. Management of CyanoHABs is complicated by the temporal and spatial dynamic nature of these events, and by the large diversity of cyanobacteria species. Identification of the dominant cyanobacteria species is required to select appropriate mitigation and treatment alternatives. Therefore, water authorities have longed for reliable tools to support proactive and species-targeted CyanoHAB management. Emerging monitoring technologies and data-driven models represent a tangible opportunity to optimise CyanoHABs management by integrating rapid and taxa precise features into a single tool. Optical sensors, namely in-situ fluorescence sensors, allow rapid, remote estimation of the total phytoplankton and cyanobacteria concentration in a waterbody. This is done by measuring the fluorescence of the pigments chlorophyll a, common to all phytoplankton, and phycocyanin, exclusive to cyanobacteria. However, fluorescence estimates have limited taxa precision because they cannot discriminate between cyanobacteria species, and may have reduced accuracy, due to optical interferences. Data-driven models are increasingly being used to understand and predict complex ecological patterns, including cyanobacteria species succession, but the combination of high-frequency fluorescence data with data-driven models to optimise CyanoHAB management has seldom been investigated.
The aim of this doctoral thesis is to develop an integrated model able to optimise CyanoHAB management by incorporating site-specific drivers of cyanobacteria succession and factors that affect fluorescence sensor estimates. This aim was achieved by addressing four objectives: (1) to systematically review the state-of-knowledge of forecasting and predictive CyanoHAB models and their application to freshwater lakes; (2) to test and quantify interferences, if any, on fluorescence probe measurements according to diel light variability and species composition; (3) to identify and quantify, through observational data analysis, dominance of cyanobacteria species according to site-specific environmental conditions; and (4) to establish a framework for implementation of integrated models considering fluorescence sensor calibration and prediction of cyanobacteria species succession.
This research project’s combination of observational data analysis and analytical laboratory work underpins its novelty and relevance. Observational data analysis was performed for three Australian drinking-water reservoirs and correlations between environmental drivers and dominance of key cyanobacteria species were determined for Wivenhoe Lake (Queensland), Tingalpa Reservoir (Queensland) and Myponga Reservoir (South Australia). Two sets of controlled laboratory experiments were then performed. The first experiment analysed the fluorescence characteristics of four key cyanobacteria species (Aphanocapsa sp., Microcystis aeruginosa, Dolichospermum circinale and Raphidiopsis raciborskii) that are often dominant in the assessed drinking-water reservoirs. The experiment quantified the variability of the species’ fluorescence characteristics throughout their respective growth phases and also compared the differences among morphologically similar species. The second experiment analysed light-induced quenching in a cyanobacterium (Dolichospermum variabilis) and a green alga (Ankistrodesmus gracilis) by simulating diel light variability under controlled temperature and stratification conditions. Lastly, a framework combining the methodological procedures from the observational data analysis and the fluorescence calibration experiments was established with the aim of supporting the development of species-targeted models utilizing fluorescence sensors. An integrated model based on the framework was developed and tested in Myponga Reservoir, South Australia. Moreover, a continuous improvement process for CyanoHAB models and guidelines of best practices for fluorescence sensors deployment, calibration and operation were developed as a result of this research.
The methods and findings are provided in four peer-reviewed journal papers included as chapters in this thesis (i.e., chapters 3, 5, 6 and 7) and a final discussion chapter (chapter 8). Objective 1 findings revealed that high-frequency data, such as the data from optical sensors, can improve performance of CyanoHAB models. For Objective 2, two key findings should be highlighted. First, fluorescence per cell was found to significantly vary among species, while fluorescence per unit of biomass (estimated from biovolume) was much more consistent among species. Second, diel light variability reduced fluorescence for both cyanobacteria and green algae up to 79% under the assessed conditions. Objective 3 findings indicated that environmental drivers for cyanobacteria succession and dominance are mostly site-specific. Species-specific traits, such as diazotrophy and gas vesicles, interact in complex ways with local environmental conditions leading to variable dominance succession among species. Finally, the key findings of Objective 4 showed that the required steps to develop a species-targeted CyanoHAB model using fluorescence sensors are feasible, given that constraints in data availability are met. Overall, the findings of this PhD research indicate that CyanoHAB management can be optimised through the combination of fluorescence sensors and forecasting models based on data-driven approaches, as long as rigorous calibration and data analysis procedures are undertaken. Importantly, the findings also highlight that even though generalisable patterns of species-specific drivers exist, site-specific analysis is required due to the complex interactions between the several factors involved in the occurrence of CyanoHABs.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Eng & Built Env
Science, Environment, Engineering and Technology
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Hobbs, Erin B. "Distribution and feeding behavior of early life stages of the northern shrimp, Pandalus borealis, in relation to the spring phytoplankton bloom in the western Gulf of Maine /." Restricted access (UM), 2008. http://libraries.maine.edu/gateway/oroauth.asp?file=orono/etheses/37803141.pdf.
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Burleson, Cheska. "Production of Bioactive Secondary Metabolites by Florida Harmful Bloom Dinoflagellates Karenia brevis and Pyrodinium bahamense." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/3998.
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Despite the critical role algae serve as primary producers, increases or accumulation of certain algae may result in Harmful Algal Blooms (HABs). Algal toxins from these blooms contribute significantly to incidences of food borne illness, and evidence suggests HABs are expanding in frequency and distribution. Mitigation of these HABs without knowledge of the ecological purpose and biochemical regulation of their toxins is highly unlikely. The production, function, and potential of secondary metabolites produced by the dinoflagellates Karenia brevis and Pyrodinium bahamense, were investigated.
Brevetoxins were demonstrated by two different methods to localize within the cytosol of Karenia brevis. Differential and density-dependent centrifugation followed by Enzyme Linked Immunosorbant Assays (ELISAs) indicated that brevetoxin was not contained by any cellular organelles. Light microscopy of brevetoxin immunolabeled preserved cells visually confirmed these results, showing stain to be distributed throughout the cytosol and notably absent from the nucleus. These results have implications for brevetoxin synthesis and function. The complex cyclization process of brevetoxin therefore likely occurs in the cytosol after export of a polyketide precursor from the chloroplast. Functionally, this cellular location suggests use of brevetoxin in cytosolic functions such as signaling and chelation.
Culture experiments of Pyrodinium. bahamense var. bahamense were undertaken to determine the effects of nutrients and environmental conditions on growth requirements and toxin production. HPLC analysis was employed to separate and quantify the saxitoxins. As eutrophication is a concern where this species is most problematic, in the Indian River Lagoon area of Florida, utilization of urea and ammonium were explored and compared to nitrate. While all nitrogen conditions yielded similar growth curves in P. bahamense, the cultures using urea contained a substantially lesser amount of the potent STX congener. This difference implies the urease enzyme utilized by P. bahamense is inefficient and urea based fertilizers are unlikely to create blooms with greater toxicity. Cyst production in P. bahamense was found to depend on nutrient limitation. Cultures utilizing ammonium displayed a smaller proportion of cysts, presumably attributable to the bioavailablility of ammonium. The total toxin content of P. bahamense was found to vary inversely with growth rate, although mole percents of the saxitoxins were largely unchanged over a suite of environmental parameters including temperature, salinity, and pH. Possible reasons for the reported increase in HABs include global warming, dumping of ballast water, and nutrient influx. These studies outline controls on toxin synthesis and production and conditions needed for growth and will aid in predicting environmental and human health effects pending these global changes.
Extracts of K. brevis and P. bahamense cultures were assayed against various pathogenic agents. Growth of K. pneumoniae was inhibited by extracts of both K. brevis and P. bahamense. An extract of K. brevis additionally inhibited MRSA, while a P. bahamense extract additionally inhibited both S. aureus and MRSA as well as the most common protozoan vector of malaria, P. falciparum. The activity of a dinoflagellate against an Apicomplexan (P. falciparum) found in this study is especially interesting as the phyla are closely phylogenetically related. Differences in activity of extracts against P. falciparum between a clonal culture on P. bahamense from the Indian River Lagoon and a 2011 bloom sampled from Tampa Bay were observed. Drugs are losing their effectiveness against these infectious agents, making pursuit of new drugs an important field. These results suggest that HAB dinoflagellates hold promise in drug discovery similar to other phytoplankton.
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Hinz, Daria J. "Emiliania huxleyi and climate change : a genetic and biogeographic investigation of bloom dynamics for a key phytoplankton species in the global carbon cycle." Thesis, University of Southampton, 2010. https://eprints.soton.ac.uk/191961/.
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Emiliania huxleyi is a ubiquitous coccolithophore present throughout the global ocean and capable of forming large blooms with significant effects on the global carbon cycle. Developing our understanding of E. huxleyi ecology is necessary in order to better quantify E. huxleyi’s role in the present carbon cycle, and to predict its role in the future carbon cycle under climate change scenarios. Major gaps in the understanding of E. huxleyi ecology were addressed using (1) controlled mesocosm experiments in June 2008 in Raunefjord, Norway, to map population genetics of E. huxleyi blooms in relation to ecological pressures (viruses and rapid growth), (2) biogeographic sampling of nannoplankton (2 - 20 μm) in the SO, including E. huxleyi, to determine ecological pressures on E. huxleyi blooms in situ (environmental gradients), and (3) controlled iron (Fe) addition bioassay experiments in the SO to establish the role of Fe gradients in the nannoplankton community relative to the phytoplankton community. During the mesocosm experiments, 279 individual E. huxleyi cells were isolated to establish clonal cultures, of which 143 were successfully genotyped using 5 microsatellite molecular markers. Both high gene diversity and two distinct genotypic populations were detected over the bloom time series and are strong evidence for a large reservoir of genetic variability within the E. huxleyi species concept, which may translate into phenotypic plasticity, such as differing levels of viral resistance. In the SO, the spatial and temporal biogeography of the three most numerous mineralizing nannoplankton groups, the coccolithophore E. huxleyi, the smaller (<20 μm) species of the diatom genus Fragilariopsis, and chrysophytes of the genus Tetraparma were defined using scanning electron microscopy (SEM) analysis in conjunction with an array of biological, physical, and chemical variables during two successive cruises to the Scotia Sea. Multivariate statistical analyses were used to identify the most influential environmental variables controlling mineralizing nannoplankton biogeography. Sea surface temperature (SST) and salinity were identified as primary variables and removed from the analysis, leaving frontal boundaries, macronutrient, and dFe concentrations significantly associated with a northern E. huxleyi-dominated community (group I; higher nutrients) and a southern Tetraparma- and Fragilariopsisdominated community (group II; lower nutrients). Estimates of biomass indicated that the Scotia Sea mineralizing nannoplankton community formed a substantial part (on average 13%) of the total phytoplankton community. The results of bioassay Fe incubations indicated a response in medium and large diatoms and E. huxleyi, and a number of microplankton (20 – 200 μm) diatom species. Overall, the work contributes substantially to our understanding of the molecular population structure, extent of phenotypic plasticity, and environmental parameters affecting the key phytoplankton E. huxleyi.
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Rankin, Samuel Christopher. "Harmful Algal Bloom (HAB) Communities and Co-Occurring Species in Relation to Near Shore Ocean Dynamics in San Luis Bay, California." DigitalCommons@CalPoly, 2011. https://digitalcommons.calpoly.edu/theses/570.
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The occurrence of phytoplankton taxa, with special focus on harmful algal bloom (HAB) taxa, was monitored for one year off the central coast of California to examine both their co-occurrence and physical and chemical variables influencing their temporal patterns. Bi-weekly samples were taken from October 6, 2008 to October 5, 2009 in San Luis Obispo Bay, CA. Canonical correspondence analysis (CCA) of weekly samples indicated that 46.1% of the variability in species abundance was explained by the variables in the model, higher than previous reports. Cluster analysis divided phytoplankton communities into HAB and non-HAB groups of species, while shared distribution analysis identified specific co-occurring species of HABs. The HAB dinoflagellate group consisted exclusively of HAB taxa, including Cochlodinium polykrikoides Margalef, Dinophysis acuminata Claparède & Lachmann, and Alexandrium spp., and was correlated with a homogeneous water column and high nitrate concentration during the fall and winter seasons. The domoic acid producing diatoms Pseudo-nitzschia seriata (Cleve) H. Peragallo complex and Pseudo-nitzschia delicatissima (Cleve) Heiden complex grouped with several other non-HAB diatoms, and were correlated with warm, thermally stratified waters of the summer season. These results contradict the classic diatom / dinoflagellate succession theory and suggest that event-scale processes influencing water column stability within seasons may influence the distribution of HAB species in near shore upwelling dominated regions.
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Schulz, Isabelle Katharina [Verfasser], Philipp [Akademischer Betreuer] Assmy, Victor [Akademischer Betreuer] Smetacek, and Kai [Akademischer Betreuer] Bischof. "Mechanisms determining species succession and dominance during an iron-induced phytoplankton bloom in the Southern Ocean (LOHAFEX) / Isabelle Katharina Schulz. Gutachter: Victor Smetacek ; Kai Bischof. Betreuer: Philipp Assmy." Bremen : Staats- und Universitätsbibliothek Bremen, 2013. http://d-nb.info/1072078619/34.
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Eiler, Alexander. "The Niches of Bacterial Populations in Productive Waters : Examples from Coastal Waters and Four Eutrophic Lakes." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7419.
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Godrant, Aurélie. "The role of superoxide in iron acquisition by marine phytoplankton." Brest, 2009. http://www.theses.fr/2009BRES2061.
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Le rôle clef du fer dans le cycle biogéochimique du carbone et de l’azote dans l’océan a été mis en évidence au cours de la dernière décennie. Une des découvertes majeures récentes en océanographie biologique est la limitation de la croissance du phytoplancton par la disponibilité en fer dans au moins 40% de l’océan mondial. Or, la chimie de cet élément dans l’océan est particulièrement complexe et la forme sous laquelle il est disponible pour le phytoplancton reste encore mal connue. Plusieurs mécanismes sont utilisés par le phytoplancton marin pour améliorer la solubilité du fer en eau de mer et parvenir à absorber les quantités suffisantes en fer nécessaires à leur survie. Un de ces mécanismes implique la production de radicaux superoxyde en milieu extracellulaire, ce qui accroît la bio-disponibilité du fer en eau de mer en réduisant la forme Fe(III) sous forme Fe(II), plus bio-disponible aux cellules de phytoplancton. Les objectifs principaux de ce travail étaient de i) développer une méthode appropriée pour détecter la production de superoxyde en milieu extracellular par n’importe quelle cellule de phytoplancton marin, et ii) examiner la relation entre la production extracellulaire de superoxyde et l’absorption du fer par la cyanobactérie Trichodesmium erythraeum IMS101. Une méthode de détection du superoxyde a été développée, qui utilise du red-CLA ou du MCLA, deux sondes chimiluminescentes spécifiques à la détection du superoxyde, qui ont donné des résultats fiables, même sur de très faibles quantités d’échantillons. En effet, comparée aux autres méthodes employées, la détection de la production du superoxyde par microplaques permet de réduire le volume d’échantillon par 10, et de réduire le temps d’analyse de tréplicats d’un échantillon, d’un blanc et de trois standards à 10 minutes. De plus, cette méthode présente une large gamme de travail avec une limite de détection de 0,076 pmol/s, ce qui lui confère un grand avantage pour le travail sur le phytoplancton marin. Les taux de production de superoxyde en milieu extracellulaire par la cyanobatérie Trichodesmium erythraeum ont été mesurés en condition de laboratoire et allaient de 0,93 à 16,21 pmol/trichome/h. La limitation en fer des cellules de Trichodesmium résultat en une augmentation de ce taux de production, qui a été multiplié par un facteur 2,9 entre les cellules non limitées et les cellules limitées en fer. Il a aussi été montré que la production de superoxyde suivait un rythme diurne avec une forte augmentation du taux de production en milieu du cycle « jour», spécialement marqué pour les cultures maintenues en milieu pauvre en fer. Les taux de production extracellulaire de superoxyde et d’absorption du fer par Trichodesmium ont été mesurés simultanément sur des cultures pré-limitées ou non limitées en fer. Les taux d’absorption étaient 10 fois plus élevés pour les cultures non limitées, sauf lorsqu’un composé réducteur (acide ascorbique) était ajouté. Dans ce cas, les taux d’absorption des deux cultures étaient similaires. De plus, les deux cultures ont montré une plus grande aptitude à absorber le fer lié à des ligands faibles comme le citrate. Dans l’ensemble, les résultats ont montré une relation entre la production de superoxyde et l’absorption de fer par Trichodesmium, mais aucune influence directe entre ces deux processus n’a pu être démontrée. La méthode de détection du superoxyde par microplaque a été utilisée lors de campagnes sur la Grande Barrière de corail en Australie. L’analyse de deux blooms de Trichodesmium a montré de forts taux de production de superoxyde, en cohérence avec les analyses effectuées au laboratoire. De plus, l’utilisation de cette méthode (entre autres) a permis de démontrer une accumulation d’espèces Fe(II) en concentrations biologiquement significatives, quand la concentration en superoxyde dans l’eau de mer était inférieure à 1 nM. Par contre, lorsque cette concentration se trouvait supérieure à 1nM, la plupart des espèces réduites (Fe(II)) étaient réoxidées, ce qui résultait en un fort taux de production de peroxyde d’hydrogène du à la dismutation du superoxyde. Dans l’ensemble, cette étude a permis le développement d’une méthode de détection de la production de superoxyde par le phytoplancton marin en milieu extracellulaire qui peut être utilisée au laboratoire ou en conditions d’étude sur le terrain. Nous avons aussi démontré que les cellules de Trichodesmium erythraeum IMS101 produisent de grandes quantités de superoxyde, en particulier lorsqu’elles sont limitées en fer. L’étude des taux d’absorption du fer par ces même cellules a démontré une forte relation entre ce processus et la production de superoxyde par les cellules: ces résultats sont en accord avec l’hypothèse que le modèle d’absorption du fer par le phytoplancton marin «Fe’» serait fortement influencé par ce type d’organisme capable de modifier l’équilibre redox du milieu présent à la surface des cellulesIt is hypothesised that, under iron limitation, phytoplankton cells develop biochemical mechanisms to increase their iron uptake efficiency with one of these mechanisms involving the production of superoxide in the extracellular environment that increases the bioavailability of iron in seawater by reducing Fe(III) to the more soluble Fe(II). The main objectives of this work were 1) to develop an appropriate method to detect extracellular production of superoxide by marine phytoplankton, and 2) to examine the relationship between extracellular production of superoxide and iron acquisition by Trichodesmium erythraeum. A method to measure superoxyde production is described using red-CLA and MCLA probes, yielding considerable improvement for analysis compared to other available methods. Extracellular superoxide production and iron uptake rates were measured simultaneously on iron replete and iron deplete Trichodesmium erythraeum IMS 101 laboratory cultures : iron starvation leads to a 2. 9-fold increase in superoxide production rate and 10-fold decrease in the iron uptake rate (except when a reducing compound was added) compared to iron replete cultures. Extracellular superoxide production shows a pronounced circadian rythm in iron deplete cultures, but less so in iron replete cultures. Overall, no direct impact of extracellular superoxide production by Trichodesmium is observed, but both processes are shown to be related. Both iron deplete and iron replete cultures demonstrate greater ability to uptake iron bound to weaker iron-binding ligands such as citrate. Application of the method to field studies in the Great Barrier Reef lagoon showed an accumulation of biologically significant concentrations of reduced trace metals including Fe(II) when the concentration of superoxide was lower than 1 nM. When the concentration of superoxide was higher than 1 nM, most of the reduced species were oxidised resulting in high rates of hudrogen peroxide production rates, consistent with laboratory studies. Overall, this thesis permitted the development of a method to detect superoxide production rates by marine phytoplankton cells that could be used routinely in field studies. The observations are in accord with the conclusion that fit the ongoing hypothesis that the extablished Fe' uptake model for phytoplankton would be strongly influenced by such organisms that are able to modify the redox equilibrium of the solution at their cells surface
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Lacour, Léo. "Dynamique des blooms phytoplanctoniques dans le gyre subpolaire de l'Atlantique Nord." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066685/document.
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Le gyre subpolaire de l'Atlantique Nord est le siège de la plus importante floraison (bloom) phytoplanctonique de l'océan global. Cet événement biologique majeur joue un rôle crucial sur le fonctionnement des écosystèmes océaniques et sur le cycle global du carbone. L'objectif de cette thèse est de mieux comprendre les processus bio-physiques qui contrôlent la dynamique du bloom phytoplanctonique et l'export de carbone à différentes échelles spatio-temporelles. Dans une première étude, basée sur des données satellites climatologiques, le gyre subpolaire a été biorégionalisé en fonction des différents cycles annuels de biomasse phytoplanctonique. Les conditions de mélange, couplées à l’intensité de la lumière de surface, contrôlent l’initiation du bloom printanier au sein des différentes biorégions. La nouvelle génération de flotteurs BGC-Argo a permis, dans une deuxième étude, d’explorer des processus à des échelles plus fines, en particulier pendant la période hivernale jusqu’à présent très peu étudiée. En hiver, des restratifications intermittentes et locales de la couche de mélange, liées à des processus de sous-mésoéchelle, initient des blooms transitoires qui influencent la dynamique du bloom printanier. Enfin, une troisième étude a montré que la variabilité haute-fréquence de la profondeur de la couche de mélange pendant la transition hiver-printemps joue aussi un rôle crucial sur l’export de carboneThe North Atlantic Subpolar Gyre exhibits the largest phytoplancton bloom of the global ocean. This major biological event plays a crucial role for the functioning of marine ecosystems and the global carbon cycle. The aim of this thesis is to better understand the bio-physical processes driving the dynamics of the phytoplankton bloom and carbon export at various spatiotemporal scales.In a first study, based on satellite data at a climatological scale, the subpolar gyre is bioregionalized according to distinct annual phytoplankton biomass cycles. The light-mixing regime controls the phytoplankton bloom dynamics in the different bioregions.In a second study, the new generation of BGC-Argo floats allowed for processes to be explored at a finer scale, especially during the overlooked winter season. In winter, intermittent and local restratifications of the mixed layer, triggered by sub-mesoscale processes, initiate transient winter blooms impacting the spring bloom dynamics.Finally, a third study showed how the high-frequency variability of the mixed layer depth during the winter-spring transition plays a crucial role on carbon export
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Jorge, Daniel Schaffer Ferreira. "Caracterização espectral das imagens de cor do oceano durante florações de fitoplâncton na Lagoa dos Patos." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/21/21134/tde-09042014-175320/.
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A Lagoa dos Patos (LP) é um dos ambientes oticamente complexos mais bem estudados no Brasil, e sua grande abrangência espacial, permite a união de diferentes medidas in situ com produtos de sensoriamento remoto, sendo possível entender melhor como os componentes óticos da água influenciam na sua cor. Florações de fitoplâncton possuem grande relevância ecológica e econômica, sendo o desenvolvimento de metologias simples para o seu monitoramento de vital importância. O presente trabalho utilizou produtos de coloração do oceano de imagens diárias dos sensores MODIS/Aqua e SeaWiFS durante os anos de 2002-2005, dados de modelos meteorológicos de reanálise para precipitação e velocidade do vento e dados de clorofila-a e salinidade obtidos in situ. Foi identificado que o espectro de reflectância de sensoriamento remoto é controlado pelo regime de El Niño e La Niña, variação intra anual e espacial (p<0.05), sendo a cor da água da LP em geral, característica de ambientes com alta concentração de CDOM/sedimentos ou de domínio misto. Partindo do pressuposto que o fitoplâncton domina o coeficiente de absorção da luz durante florações de fitoplâncton, e que as possíveis florações na LP se restringem a diatomáceas e cianobactérias, foi desenvolvido um modelo de classificação para discriminar a ocorrência desses eventos. O modelo proposto permite a classificação de águas oticamente complexas de acordo com o componente ótico predominante, e é pioneiro na exploração de dados do sensor MODIS/Aqua para detecção de florações de fitoplâncton em um ambiente lagunarPatos Lagoon (PL) is one of the optical complex environment best studied in Brazil, and it large spatial extent, allows the union of different in situ and remote sensing measures, enabling a better understandment of how the optical components in water can influence its color. Phytoplankton blooms have great ecological and economic relevance, and the development of simple methodologies for your monitoring of vital importance. The present work used ocean color products from daily MODIS/Aqua and SeaWiFS images during the years 2002-2005, meteorological model data for precipitation and wind speed and chlorophyll-a and sailinity data obtained in situ. It was detected that remote sensing reflectance spectra is controlled by the regime of El Niño and La Niña, intra annual and spatial changes (p<0.05), ande the water color from PL in general, characteristic of environments with high CDOM/sediments concentration or with mixed domain. Assuming that the phytoplankton dominate light absorption coefficient during phytoplankton blooms, and that PL possible blooms are restricted to diatom and cyanobacteria, a classification model was developed to discriminate the occurance of those events. The proposed model allows for the classification of optically complex waters according to the predominant optical component, and it is pioneer in the exploration of data from MODIS/Aqua sensor to detect phytoplankton blooms in lagunar environment
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Vaičiūtė, Diana. "Potencialiai toksinių planktoninių melsvabakterių erdvinio pasiskirstymo ypatumai šiaurinėje Kuršių marių dalyje." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2014. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2007~D_20140623_171705-58381.
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Dumbliai – mikroskopiniai planktono organizmai – vienas iš pagrindinių hidroekosistemų komponentų, pirminiai organinės medžiagos producentai. Didėjant vandens telkinių trofiškumui, mažėja dumblių rūšių įvairovė, keičiasi vyraujančių rūšių kompleksas. Dažnai eutrofikuotuose vandens telkiniuose ima dominuoti prokariotiniai autotrofiniai mikroorganizmai – melsvabakterės, kurios sukelia intensyvius vandens „žydėjimo“ procesus ežeruose, jūrinėse lagūnose, jūrose bei vandenynuose. Dėl šios priežasties blogėja vandens kokybė. Pastaraisiais dešimtmečiais išsamių tyrimų objektu visame pasaulyje tampa toksiniai fitoplanktono dumbliai ir melsvabakterės. Tyrimais yra nustatyta, kad pusė iš visų vandens „žydėjimo“ atvejų yra toksiški (RAPALA, LAHTI, 2002). Pasaulyje atliekami monitoringiniai tyrimai, siekiant įvertinti toksinių dumblių ir melsvabakterių vystymosi tendencijas, priklausomybę nuo aplinkos sąlygų, toksinio vandens „žydėjimo“ priežastis. Pasitelkiant cheminius bei genetinius metodus, nustatoma toksinių medžiagų cheminė sudėtis, vertinamas jų poveikis gyviems organizmams. Šiaurinės Kuršių marių dalies vasariniame planktone 2004-2006 m. aptiktos 223 dumblių rūšys, priklausančios 5 klasėms. 97 rūšys (43 %), priklauso Chlorophyceae klasei, 71 rūšis (32 %) – Cyanophyceae, 40 rūšių (18 %) – Bacillariophyceae, 9 rūšys (4 %) – Euglenophyceae ir 6 rūšys (3 %) – Dinophyceae klasei, iš jų aptiktos 26 potencialiai toksinės dumblių ir melsvabakterių rūšys, priklausančios 3 klasėms, 14... [toliau žr. visą tekstą]Curonian Lagoon is a shallow transitional water basin located in the south-eastern part of the Baltic Sea. The southern and central parts of the lagoon contain freshwater due to discharge from the Nemunas River, while the salinity in the northern part varies from 0 to 8 PSU, depending on winds activity affecting brackish water inflow from the Baltic Sea. The investigation was carried out in the fresh-brackish water mixing zone (Influence zone of Baltic Sea), in the central part and Nemunas River influence zone in July-August 2004 - 2006. Changes in physico-chemical parameters, chlorophyll a concentration, phytoplankton and toxic algae cell density were monitored. Totally 223 species and varieties mainly belonging to Chlorophyceae (43 %) and Cyanophyceae (32 %) were found. 26 algae species from 3 algae classes (Cyanophyceae, Chlorophyceae and Dinophyceae) were identified as potential toxic species in the northern part of Curonian Lagoon during 2004 and 2006 summer time. Dominated toxic species Ahpanizomenon flos-aquae, Microcystis aeruginosa, M. viridis, M. wesenbergii, Woronichinia compacta. Phytoplankton biomass in Curonian Lagoon surface ranged from 12,27 to 50,22 mg/l. The peak of phytoplankton (33,11 mg/l) and potential toxic algae (28,67 mg/l) biomass in 2004 summer time was observed near by Klaipeda Strait, were Aphanizomenon flos-aquae contain 36 % from total biomass. In 2005 summer time the highest phytoplankton (50,22 mg/l) and toxic algae (21.46 mg//l) biomass were... [to full text]
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Irion, Solène. "Biodiversité de l'écosystème marin et flux de carbone autour de Kerguelen (Océan Austral) : le rôle du petit phytoplancton à l'échelle de la cellule Marked spatiotemporal variations in small phytoplankton structure in contrasted waters of the Southern Ocean (Kerguelen area) Small phytoplankton contribute greatly to CO2-fixation after the diatom bloom in the Southern Ocean." Thesis, Littoral, 2020. https://tel.archives-ouvertes.fr/tel-03178263.
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Cette thèse s'intéresse à la diversité du petit phytoplancton (<20 µm) et à sa contribution à la fixation du carbone dans les écosystèmes marins contrastés : la région productive du plateau de Kerguelen d'une part et les zones à faible productivité en dehors du plateau, d'autre part. Le petit phytoplancton domine les communautés phytoplanctoniques tout au long de l'année en dehors du plateau, où les faibles concentrations en fer limitent la production primaire. Le plateau de Kerguelen, naturellement fertilisé en fer, est quant à lui caractérisé par le développement au printemps-été de blooms massifs de diatomées en chaîne et de grande taille. Depuis la découverte du mécanisme de fertilisation naturelle en fer sur le plateau, l'attention de la communauté scientifique s'est focalisée sur les diatomées de grande taille, qui favoriseraient la séquestration du carbone sur la zone. Toutefois, les données satellitaires suggéraient que le petit phytoplancton dominait les communautés phytoplanctoniques en dehors du bloom sur l'ensemble de la zone. Le premier objectif de ce travail visait à obtenir une image fine de la diversité du petit et grand phytoplancton après le bloom de diatomées (Mars 2018). Un fragment de l'ADNr 18S des communautés planctoniques de petite (0.2-20 µm) et grande taille (20-100 µm), collectées à plusieurs profondeurs, a été séquencé par la méthode Illumina MiSeq. Les séquences ainsi obtenues ont permis de déterminer la diversité taxonomique moléculaire du petit et grand phytoplancton. En surface, les diatomées étaient majoritaires dans la grande fraction de taille tandis que Phaeocystis antartica était particulièrement important dans la petite fraction sur l'ensemble de la zone d'étude. Dans leur ensemble, les communautés de petit phytoplancton différaient sur et en dehors du plateau. Des concentrations élevées en acide silicilique en dehors du plateau favorisaient la présence d'un assemblage varié de diatomées de petite taille, tandis que de fortes concentrations en ammonium sur le plateau pourraient favoriser le développement de picophytoplancton du genre Micromonas. L'utilisation de marqueurs pigmentaires chémotaxonomiques a permis de décrire la succession temporelle des communautés phytoplanctoniques sur le plateau, dominées par les diatomées du début au déclin du bloom, tandis que la contribution du petit phytoplancton augmentait fortement après le bloom (moins de 10% à 53% de la chlorophylle). Le deuxième objectif de cette thèse était d'établir la contribution relative de différents groupes phytoplanctoniques à la fixation globale de carbone, en prenant en compte les différences inter- et intra-groupe dans l'activité métabolique de cellules individuelles. Pour ce faire, des communautés planctoniques naturelles ont été incubées en présence d'un traceur isotopique (NaH¹³CO₃) en reproduisant les conditions in situ. La fixation du carbone au niveau cellulaire a été mesurée par imagerie NanoSIMS et SIMS. Les grandes diatomées (>20 µm) montraient des taux de croissance faibles et variables d'une cellule à l'autre, avec 19±13% de diatomées inactives. Inversement, les petites cellules, appartenant à des taxons phylogénétiques éloignés (prymnesiophytes, prasinophytes et petites diatomées) étaient majoritairement en croissance active (>98%). Par conséquent, le petit phytoplancton contribuait de 41 à 70% à la fixation du carbone sur l'ensemble de la zone après le bloom. Tandis que le petit phytoplancton contribuait de façon importante à la fixation de carbone et à la biomasse chlorophyllienne en surface, les diatomées dominaient dans les données pigmentaires et de séquençage en dessous de 200 m, indiquant leur export préférentiel par sédimentation directe. Cependant, un faisceau d'indices suggère que le phytoplancton de petite taille, en particulier Phaeocystis, pourrait participer à l'export de carbone par agrégation, ainsi que via les réseaux trophiques et la production de pelotes fécales des brouteursThis thesis focuses on small phytoplankton diversity (<20 µm) and its contribution to CO₂-fixation in contrasted marine ecosytems : the productive Kerguelen Plateau (KP) on the one hand and low productive surrounding waters on the other han. Iron-limited phytoplankton communities off-plateau are dominated by small cells all year long, whereas natural iron-fertilization over the KP promotes the seasonal development of chain-forming or large diatom blooms in spring and summer. Since the demonstration of natural iron fertilization on-plateau, the scientific community focused on large diatoms, assumed to promote carbon sequestration in the area. However, satellite data suggest that small phytoplankton dominate the phytoplankton communities outside of the bloom period on- and off-plateau. Consequently, this thesis had two main objectives. The first objective of this work was to obtain a precise image of the diversity of small and large phytoplankton after the diatom bloom (March 2018). A fragment of the 18S rRNA gene from small (0.2-20 µm) and large (20-100 µm) planktonic communities collected at discrete depths (down to 300 m), was sequenced (Illumina MiSeq) and used as an identity marker gene to determine the taxonomic diversity of small and large phytoplankton. At the surface, diatoms were dominant in the large-size fraction, while Phaeocystis antartica was particularly abundant in the small-size fraction, over the entire study area. As a whole, small phytoplankton communities were significantly different on- and off-plateau. High concentrations of silicic acid off-plateau favored the presence of a diverse assemblage of small diatoms, while high concentrations of ammonium on-plateau likely promoted the development of pico-sized Micromonas. Using chemotaxonomic pigments markers allowed the description of the temporal succession of phytoplankton communities on-plateau, dominated by diatoms from the onset to the decline of the bloom, while the contribution of small phytoplankton increased sharply after the bloom (less than 10% to 53% chlorophyll). The second objective of this thesis was to establish the relative contribution of different phytoplankton groups to bulk CO₂-fixation, considering inter- and intra-group differences in the metabolic activity if individual cells. To do so, natural planktonic communities were incubated mimicking in situ conditions in the presence of an isotopic tracer (NaH¹³CO₃). CO₂-fixation by small and large cells was then measured at the single cell level by NanoSIMS and SIMS imaging (mass spectrometry with lateral resolution of 50 nm and 1 µm, respectively). Large diatoms (> 20 µm) showed highly variable growth rates with 19±13 % inactive diatoms, whereas small cells, affiliated to distant phylogenetic taxa (prymnesiophytes, prasinophytes and small diatoms) were actively growing (>98%). This showed that small phytoplankton contributed to 41-70% of CO₂-fixation over the entire area after the bloom. While small phytoplankton contributed significantly to CO₂-fixation and chlorophyll biomass at the surface, diatoms dominated in pigment and sequencing data below 200 m, indicating their preferential export by direct sedimentation. However, a body of evidence suggests that small phytoplankton, in particular Phaeocystis, may contribute to carbon export through aggregation, as well as via the production of fecal pellets from grazers
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Louchart, Arnaud. "Dynamique spatio-temporelle des communautés phytoplanctoniques côtières et de leurs caractéristiques intrinsèques, à partir d'une approche automatisée à haute résolution Phytoplankton distribution from Western to Central English Channel, revealed by automated flow cytometry during the summer-fall transition Spatial niches of phytoplankton functional groups assessed during a spring bloom development in two temperate coastal seas Untangling the vertical distribution of phytoplankton groups along a salinity gradient through the Baltic Sea and the Skagerrak-Kattegat straits." Thesis, Littoral, 2020. http://www.theses.fr/2020DUNK0556.
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Au sein des écosystèmes côtiers, la composition, la distribution et la dynamique phytoplanctoniques sont influencées par les variations spatio-temporelles des structures hydrologiques et des para mètres biogéochimiques, sous les pressions naturelles et anthropiques. Les suivis de référence, de par leur faible résolution spatiale et temporelle, peuvent manquer des événements-clés comme l'initiation ou la fin des efflorescences ou nuisibles (du type Harmful Algal Blooms). Pour permettre leur détection et mieux comprendre la distribution et la dynamique de ce compartiment à la base des réseaux trophiques et acteur majeur des cycles biogéochimiques, l'utilisation d'approches automatisées à haute fréquence permet de compléter les approches taxonomiques par la caractérisation fonctionnelle de l'ensemble du spectre de taille du phytoplancton. Cette thèse est consacrée à l'étude des caractéristiques morphologiques et physiologiques des groupes fonctionnels phytoplanctoniques définis à partir de leurs propriétés optiques à l'échelle de l'individu, rencontrés dans des mers épi-et intracontinentales contrastées en utilisant la cytométrie en flux automatisée de type "pulse-shape-recording". Tout d'abord, la distribution des groupes phytoplanctoniques et de leurs traits ont été explorés en Manche occidentale et centrale lors de la transition été-automne, ce qui a permis de mettre en évidence la formation de patches d'abondance et de biomasse à proximité du front d'Ouessant et une structuration à sub-mésoéchelle. En deuxième lieu, la dynamique des groupes fonctionnels phytoplanctoniques en Manche orientale et sud Mer du Nord a été étudiée pendant la période de développement des blooms printaniers de diatomées et de Phaeocystis globosa, avec l'utilisation de la LCBD et de la SCBD permettant l'observation de ségrégation spatiale entre groupes phytoplanctoniques dont leur distribution est expliquées par les paramètres de niche (marginalité et tolérance). Enfin, l'étude des paramètres conditionnant la distribution spatiale verticale le long d'un gradient de salinité en Mer Baltique a été abordée pendant la période estivale, en relation avec les propriétés biogéochimiques des masses d'eaux, qui a permis d'identifier les caractéristiques des groupes phytoplanctoniques participant à la distribution des groupes phytoplanctoniques. Les variations des traits ressortent comme étant les meilleurs prédicteurs de la distribution horizontale et verticale vis-à-vis des paramètres de niche et des descripteurs spatiaux (dispersion, paramètres physiques et biologiques). L'approche par traits fonctionnels, dérivés des mesures optiques à haute résolution, couplée à l'analyse de niche permettent d'avancer dans la compréhension des réponses des communautés aux gradients environnementaux, elles-mêmes détectées par les mesures d'indices de diversité. Ce travail a bénéficié de l'appui des projets régionaux (CPER MARCO), nationaux (convention MTES-CNRS) et européens (JERICO-NEXT)In coastal ecosystems, phytoplankton composition, distribution and dynamics are strongly influenced by spatial and temporal variations of hydrological structures and biogeochemical parameters, consequences of natural and anthropogenic pressures. Reference monitoring, due to its low spatial and temporal resolution, may fail to detect key events as the initiation and end of phytoplankton outbursts or harmful algal blooms (HABs). By increasing the spatial and/or temporal resolution as well as completing taxonomical counting by investigating the phytoplankton whole size spectra, the use of automated sensors may allow contributing to a better understanding of the distribution and dynamics of this major player in biogeochemichal cycles, at the basis of most foof webs. This thesis consists in studying the characteristics of phytoplankton functional groups defined from their optical properties at the single-cell level, in relation to spatio-temporal variability encountered in contrasting marginal seas, applying the pulse shape-recording automated flow cytometry. This functional classification reflects the diversity of particles according to morphological and physiological properties. First of all, the distribution of phytoplankton groups and their traits where explored in the Western and Central English Channel during the summer period. Most groups formed patches of abundance and biomass near the Ushant front and were structured at the sub-mesoscale. Secondly, phytoplankton functional groups dynamics was characterized in the Eastern English Channel and Southern North Sea during the development period of diatoms and Phaeocystis globosa spring groups, by calculating LCBD and SCBD, wich allowed the observation of spatial segregation between phytoplankton groups. Their distribution was explained by the niche parameters (marginality and tolerance). Finally, the vertical distribution of phytoplankton functional groups in a salinity gradient was addressed in the Baltic Sea, in relation to the biogeochemical properties of the water masses and the characteristics of each PFGs. The variations of the traits are thus stand out as the best predictors of the horizontal and vertical distribution of phytoplankton groups with the respect to niche parameters and spatial descriptors (dispersion, physical and biological parameters). The functional approach, derived from phytoplankton optical properties addressed by automated flow cytometry, coupled to the niche analysis, make it possible to better explain and predict community responses to environmental gradients, such responses being detected in parallel by diversity indices. This work benefited from the support of local (MARCO State-Region Plan Contract), national (CNRS-MTES convention) and international European H2020 JERICO-NEXT projects
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Lacour, Léo. "Dynamique des blooms phytoplanctoniques dans le gyre subpolaire de l'Atlantique Nord." Electronic Thesis or Diss., Paris 6, 2016. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2016PA066685.pdf.
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Le gyre subpolaire de l'Atlantique Nord est le siège de la plus importante floraison (bloom) phytoplanctonique de l'océan global. Cet événement biologique majeur joue un rôle crucial sur le fonctionnement des écosystèmes océaniques et sur le cycle global du carbone. L'objectif de cette thèse est de mieux comprendre les processus bio-physiques qui contrôlent la dynamique du bloom phytoplanctonique et l'export de carbone à différentes échelles spatio-temporelles. Dans une première étude, basée sur des données satellites climatologiques, le gyre subpolaire a été biorégionalisé en fonction des différents cycles annuels de biomasse phytoplanctonique. Les conditions de mélange, couplées à l’intensité de la lumière de surface, contrôlent l’initiation du bloom printanier au sein des différentes biorégions. La nouvelle génération de flotteurs BGC-Argo a permis, dans une deuxième étude, d’explorer des processus à des échelles plus fines, en particulier pendant la période hivernale jusqu’à présent très peu étudiée. En hiver, des restratifications intermittentes et locales de la couche de mélange, liées à des processus de sous-mésoéchelle, initient des blooms transitoires qui influencent la dynamique du bloom printanier. Enfin, une troisième étude a montré que la variabilité haute-fréquence de la profondeur de la couche de mélange pendant la transition hiver-printemps joue aussi un rôle crucial sur l’export de carboneThe North Atlantic Subpolar Gyre exhibits the largest phytoplancton bloom of the global ocean. This major biological event plays a crucial role for the functioning of marine ecosystems and the global carbon cycle. The aim of this thesis is to better understand the bio-physical processes driving the dynamics of the phytoplankton bloom and carbon export at various spatiotemporal scales.In a first study, based on satellite data at a climatological scale, the subpolar gyre is bioregionalized according to distinct annual phytoplankton biomass cycles. The light-mixing regime controls the phytoplankton bloom dynamics in the different bioregions.In a second study, the new generation of BGC-Argo floats allowed for processes to be explored at a finer scale, especially during the overlooked winter season. In winter, intermittent and local restratifications of the mixed layer, triggered by sub-mesoscale processes, initiate transient winter blooms impacting the spring bloom dynamics.Finally, a third study showed how the high-frequency variability of the mixed layer depth during the winter-spring transition plays a crucial role on carbon export
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Dadaglio, Laëtitia. "Dynamique des communautés bactériennes en réponse au bloom phytoplanctonique dans l’océan Arctique et identification des acteurs microbiens impliqués dans la dégradation de la matière organique." Electronic Thesis or Diss., Sorbonne université, 2018. http://www.theses.fr/2018SORUS488.
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Le réchauffement climatique conduit à une diminution drastique de l’étendue et de l’épaisseur de la banquise entrainant un allongement et une intensification du bloom phytoplanctonique Arctique. L’augmentation de la production primaire pourrait modifier le fonctionnement de cet écosystème ainsi que les communautés bactériennes (CB) impliquées dans la dégradation de la matière organique (MO). Les objectifs de cette thèse étaient (1) de décrire la dynamique spatiale et temporelle in situ des CB lors du développement du bloom ; et (2) d’identifier expérimentalement les acteurs bactériens responsable de la dégradation de la MO excrétée par des microalgues arctiques. Les résultats montrent une forte réactivité des CB en réponse au bloom lors du retrait de la banquise, avec des maxima simultanés entre la chla et l’abondance bactérienne. Des modifications dans la composition des CB (CCB) ont lieu avant et au cours du bloom avec une diminution de la diversité. L’acclimatation rapide des CB à cette nouvelle source de MO phytoplanctonique pourrait être favorisée par l’apport préalable de MO produite par les microalgues de glace et par le tapis algal sous la banquise. Le retrait de la banquise et le développement du bloom conduisent à une CB dominée par les Oceanospirillales et les Flavobacteriaceae. Nos résultats de terrain et expérimentaux soulignent l’importance du genre Polaribacter dans la dégradation de la MO produite lors de bloom arctique dominé par les diatomées. Ils suggèrent également qu’une modification dans la composition du bloom phytoplanctonique (en faveur des picoeucaryotes) liée au réchauffement climatique pourrait avoir des conséquences sur l’activité et la CCBGlobal warming leads to a drastic decrease in the coverage and thickness of the ice pack leading to longer and more intense Arctic phytoplankton blooms. The increase in primary production associated to the phytoplankton bloom could induce pronounced changes in the functioning of the Arctic ecosystem, in particular the bacterial communities (BC) implicated in the degradation of organic matter (OM). The objectives of the present thesis were to (1) describe the in situ temporal and spatial dynamics of the BC during the ice retreat and the spring phytoplankton bloom, and (2) identify experimentally the bacterial players responsible for the degradation of OM excreted by different Arctic microalgae. The results show a rapid response of the BC to the phytoplankton bloom during the ice retreat, with simultaneous maxima in chla and bacterial abundance. Modifications in the BC composition (BCC) appear prior and during the phytoplankton bloom with a decrease in the bacterial diversity. The rapid acclimation of the BC to the fresh phytoplankton OM could be due to preceding OM production by ice microalgae or by algal mats attached to the ice. Ice retreat and phytoplankton bloom development lead to a BC dominated by Oceanospirillales and Flavobacteriaceae. Field and experimental results highlight Polaribacter as a key player in the degradation of OM produced during diatom dominated phytoplankton blooms in the Arctic Ocean. Our results also suggest a modification in the phytoplankton community composition (towards picoeukaryotes) linked to global warming could have consequences on the activity and composition of the associated BC
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Foy, R. H. "Phytoplankton growth in Lough Neagh." Thesis, Queen's University Belfast, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333608.
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Huber, Veronika Emilie Charlotte. "Climate impact on phytoplankton blooms in shallow lakes." Phd thesis, Universität Potsdam, 2010. http://opus.kobv.de/ubp/volltexte/2010/4234/.
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Lake ecosystems across the globe have responded to climate warming of recent decades. However, correctly attributing observed changes to altered climatic conditions is complicated by multiple anthropogenic influences on lakes. This thesis contributes to a better understanding of climate impacts on freshwater phytoplankton, which forms the basis of the food chain and decisively influences water quality.
The analyses were, for the most part, based on a long-term data set of physical, chemical and biological variables of a shallow, polymictic lake in north-eastern Germany (Müggelsee), which was subject to a simultaneous change in climate and trophic state during the past three decades. Data analysis included constructing a dynamic simulation model, implementing a genetic algorithm to parameterize models, and applying statistical techniques of classification tree and time-series analysis.
Model results indicated that climatic factors and trophic state interactively determine the timing of the phytoplankton spring bloom (phenology) in shallow lakes. Under equally mild spring conditions, the phytoplankton spring bloom collapsed earlier under high than under low nutrient availability, due to a switch from a bottom-up driven to a top-down driven collapse. A novel approach to model phenology proved useful to assess the timings of population peaks in an artificially forced zooplankton-phytoplankton system. Mimicking climate warming by lengthening the growing period advanced algal blooms and consequently also peaks in zooplankton abundance.
Investigating the reasons for the contrasting development of cyanobacteria during two recent summer heat wave events revealed that anomalously hot weather did not always, as often hypothesized, promote cyanobacteria in the nutrient-rich lake studied. The seasonal timing and duration of heat waves determined whether critical thresholds of thermal stratification, decisive for cyanobacterial bloom formation, were crossed. In addition, the temporal patterns of heat wave events influenced the summer abundance of some zooplankton species, which as predators may serve as a buffer by suppressing phytoplankton bloom formation.
This thesis adds to the growing body of evidence that lake ecosystems have strongly responded to climatic changes of recent decades. It reaches beyond many previous studies of climate impacts on lakes by focusing on underlying mechanisms and explicitly considering multiple environmental changes.
Key findings show that climate impacts are more severe in nutrient-rich than in nutrient-poor lakes. Hence, to develop lake management plans for the future, limnologists need to seek a comprehensive, mechanistic understanding of overlapping effects of the multi-faceted human footprint on aquatic ecosystems.Weltweit haben Seeökosysteme auf den Klimawandel der letzten Jahrzehnte reagiert. Beobachtete Veränderungen eindeutig dem Klimawandel zuzuordnen, wird jedoch häufig dadurch erschwert, dass Seen gleichzeitig vielfachen anthropogenen Einflüssen ausgesetzt sind. Diese Arbeit trägt zu einem besseren Verständnis des Klimaeinflusses auf Algen bei, die am Anfang der Nahrungskette stehen und maßgeblich die Wasserqualität eines Sees beeinflussen können. Zum größten Teil stützt sich die Arbeit auf eine dreißigjährige Datenreihe eines unregelmäßig geschichteten Flachsees im Nordosten von Deutschland (Müggelsee), in dem sowohl steigende Wassertemperaturen als auch sinkende Nährstoffeinträge zu verzeichnen waren. Bei der Datenanalyse wurde ein neu erstelltes dynamisches Simulationsmodell, genetische Algorithmen zur Parametrisierung von Modellen, und statistische Methoden der Klassifizierung und Zeitreihenanalyse genutzt. Ergebnisse dieser Arbeit zeigen, dass nicht nur klimatische Faktoren sondern auch die Nährstoffverfügbarkeit im See den Zeitpunkt der Algenfrühjahrsblüte (Phänologie) beeinflussen. Durch eine Veränderung der Mechanismen, die zum Kollaps der Blüte führen, trat diese trotz ähnlich milder Winterbedingungen bei hoher Nährstoffverfügbarkeit früher auf als bei niedriger. Ein neuentwickelter Ansatz zur Modellierung von Phänologie erwies sich als geeignet, um vorherzusagen, wann Algen und ihre Räuber in einem künstlich periodisch angetriebenen Laborsystem ihre Populationshöhepunkte erreichten. Eine Verlängerung der Wachstumsperiode führte dazu, dass diese früher auftraten. Die Untersuchung, warum sich Blaualgen im betrachteten See während jüngster Hitzewellenereignisse überraschend unterschiedlich entwickelt hatten, ergab, dass ungewöhnlich warmes Wetter nicht wie häufig vermutet generell förderlich für ihre Entwicklung ist. Der Zeitpunkt und die Dauer der Hitzewellen waren entscheidend dafür, ob für Blaualgen kritische Schwellenwerte der thermischen Schichtung im See überschritten wurden. Zudem zeigte sich, dass saisonale Erwärmungsmuster einen bedeutenden Einfluss auf Räuber nahmen, die das Auftreten von Algenblüten verhindern können. Diese Arbeit reiht sich in eine wachsende Anzahl von Studien ein, die zeigen, dass Seeökosysteme bereits stark auf die Klimaveränderungen der letzen Jahrzehnte reagiert haben. Mit ihrem Fokus auf Mechanismen und der expliziten Berücksichtigung simultaner anthropogener Einflüsse geht diese Arbeit gleichzeitig über viele bisherige Studien hinaus, die sich auf reine Beobachtung und die Betrachtung klimatischer Faktoren beschränkten. Kernergebnisse deuten daraufhin, dass Klimafolgen in nährstoffreichen Seen stärker ausfallen als in nährstoffarmen Seen. Nur mit einem umfassenden, mechanistischen Verständnis des vielfältigen anthropogenen Einflusses wird eine hohe Wasserqualität in Seen auch in Zukunft aufrechtzuerhalten sein.
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Nauman, Callie A. "The Spatial and Temporal Distribution and Environmental Drivers of Saxitoxin in Northwest Ohio." Bowling Green State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1589644025246293.
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Wolmarans, Karien. "The influence of nutrients on surf-zone phytoplankton." Thesis, Nelson Mandela Metropolitan University, 2012. http://hdl.handle.net/10948/d1008080.
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The variability in surf-zone phytoplankton community composition together with variability in nutrient concentrations was studied at seven beaches along the coast near Port Elizabeth, South Africa over a one-year sampling period. The nutrient requirements of selected diatoms and dinoflagellates that co-occur at these beaches were studied. The highest nutrient concentrations were recorded at Brighton beach, with phosphate concentration being substantially higher than standards set out for both South African and European waters. Nitrate, ammonium and silicate concentrations were consistent (low variability) at all beaches. The species composition of beaches without surf diatoms was also not variable (except for King’s Beach – an artificial beach). Maitland beach was the only beach that could be identified as a surf diatom beach due to the presence of Anaulus australis. The surf diatom Anaulus australis was found to be a superior competitor compared to all other species tested: the other surf diatom Asterionellopsis glacialis, and the dinoflagellates Gonyaulax spinifera, Prorocentrum micans, and Scrippsiella trochoidea. Gonyaulax spinifera could possibly outcompete Anaulus australis in systems should nitrate become limiting.
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Fandino, Laura B. "Molecular ecology of bacteria associated with marine phytoplankton blooms /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2002. http://wwwlib.umi.com/cr/ucsd/fullcit?p3064445.
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Prentice, Matthew J. "Phosphorus sources contributing to phytoplankton blooms in a subtropical reservoir." Thesis, Griffith University, 2021. http://hdl.handle.net/10072/408508.
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Lakes comprise 87% of surface freshwater existing in liquid form on Earth. In recent years, however, lake condition has deteriorated at an alarming rate primarily attributed to an increase in anthropogenic-related nutrient inputs. These inputs present the greatest challenge to lake ecosystem stability as they cause eutrophication, which is often characterised by deoxygenation of bottom waters and phytoplankton blooms. Blooms of cyanobacteria are of particular concern as some species or strains produce toxins that affect biodiversity and organisms that are part of the foodweb, as well as causing sickness and death of livestock, wildlife, and humans reliant on lakes for water consumption. In addition, cyanobacteria may also produce taste and odour-causing compounds, increasing water treatment costs. It is therefore imperative to develop an understanding of the drivers contributing to cyanobacteria blooms so that blooms may be better understood and predicted, as well as their effects mitigated.
Phosphorus (P) is an essential element for all organisms—including phytoplankton—and in lakes is widely considered to be the key nutrient limiting or co-limiting (with nitrogen [N]) phytoplankton productivity. Excess P can alter phytoplankton communities and lead to phytoplankton blooms. The forms of P are usually determined operationally as: 1) particulate organic P (POP), including P in living and dead organisms; 2) particulate inorganic P (PIP), including inorganic complexes of P sorbed to mineral phases of rock and soil; 3) dissolved organic P (DOP), including low molecular-weight esters and organic colloids; and 4) dissolved inorganic P (DIP; or soluble reactive P [SRP]; or dissolved reactive P [DRP]), including orthophosphate (PO43-) and polyphosphates. Despite the DIP fraction composing the only forms able to be directly assimilated by the phytoplankton community, each fraction is in a constant state of flux and thus—on account of the action of various biogeochemical processes occurring across space and time—carries the potential to affect phytoplankton productivity. The influence of P on phytoplankton productivity is therefore highly dynamic, as a result of the transformations and transportation of P within the system.
Phytoplankton are known to upregulate high-affinity transporters that increase P uptake under DIP-depauperate conditions. Therefore—Chapter 2 (i.e., the first data chapter)—examines the relationships between 1) physicochemical drivers and phytoplankton community P uptake rates, and 2) phytoplankton community P uptake and species composition, in the surface waters of the seasonally DIP-depauperate subtropical lake; Lake Wivenhoe, Queensland, Australia. P starvation was also examined in the dominant cyanobacterium Raphidiopsis raciborskii (Wołoszyńska 1912) Aguilera et al. 2018 (previously Cylindrospermopsis raciborskii) under controlled laboratory conditions. Phytoplankton P uptake was quantified using the radioisotope phosphorus-33, with field study measurements complemented by a suite of physicochemical parameters measured in the lake at monthly intervals over a 12-month period. Surface DIP concentrations and P uptake rates were demonstrated to be inversely related, with substantially higher uptake rates occurring under thermally stratified, DIP-depauperate conditions during summer. Surface DIP concentration and temperature explained 50.3% of the variation in P uptake rate, per classification and regression tree (CART). A primary split in the CART at 4.75 μg L−1 P indicated a transition between low- and high-affinity uptake, with high-affinity P uptake rates (i.e., P uptake < 4.75 μg L−1 P) associated with a phytoplankton assemblage dominated by cyanobacteria, including the dominant cyanobacterium R. raciborskii. Field results were corroborated by the in vitro P-starvation study of the R. raciborskii strain, with uptake rates increasing as the culture became progressively starved of P. These results indicate that P scavenging via high-affinity uptake is advantageous under DIP-depauperate conditions, and the ability to scavenge P via high-affinity uptake may be a key factor in the dominance of bloom-forming cyanobacteria under DIP-depauperate stratified conditions.
As demonstrated in Chapter 2, during stratified periods when DIP is low, the phytoplankton assemblage had elevated P uptake rates. Further, under these conditions, DOP became the dominant source of dissolved P (DP; i.e., DIP + DOP) available to phytoplankton. Therefore—Chapter 3 (i.e., the second data chapter)—examines how DOP mineralisation by alkaline phosphatase (AP) activity (APA), relative to regeneration processes in the SML, could meet phytoplankton P uptake and how it is associated with phytoplankton community composition changes under thermally stratified DIP-depauperate conditions in Lake Wivenhoe. APA was quantified fluorometrically using 4-methylumbelliferyl phosphate, and phytoplankton P uptake and regeneration determined radiometrically using the isotope phosphorus-33 at monthly intervals during a summer-stratified period. APA was demonstrated to increase when phytoplankton cell P quotas were low (<0.65 μg P μg−1 Chl-a), with potential DOP mineralisation rates increasing to 88 μg L−1 h−1 P. Such rates are at the upper end of rates in the literature. APA represented up to 89% of the total phytoplankton P uptake and was much higher than the P regeneration rate in the SML. The highest APA coincided with peak phytoplankton biovolume and dominance of the phytoplankton assemblage by cyanobacteria. Further, APA was strongly positively related to the majority of the 10 most dominant cyanobacteria, including the toxin-producing species R. raciborskii. This indicates that under DIP-depauperate conditions, DOP mineralised by APA is a substantial source of P for phytoplankton, and the ability to produce AP may be a key factor in the occurrence of bloom-forming cyanobacteria.
As demonstrated in Chapter 2 and Chapter 3, P fluxes strongly impact phytoplankton biomass in Lake Wivenhoe. Therefore—Chapter 4 (i.e., the third data chapter)—examines the key physical and biogeochemical fluxes of P available affecting the time-distance continuum of phytoplankton in Lake Wivenhoe. Physical transport and biogeochemical transformation was determined in the context of a horizontally-resolved mass balance, comprising four zones down the drowned river channel that forms the lake. The mass balance was informed by integrating field and laboratory measurements of selected biogeochemical P fluxes with transport fields from a hydrodynamic model (AEM3D). P regeneration within the surface waters was demonstrated as being more important than the physical processes introducing ‘new P’ into the surface waters. Vertical transport of DOP to the SML was comparable to regeneration at times during the stratified period, and advective fluxes of P were comparable to regeneration during a storm event in May of which remained elevated above pre-storm levels for several weeks. On an annual basis, the flux of P was also demonstrated to transition from one of physical to biogeochemical dominance, and the physical-component from one of horizontal to vertical dominance, longitudinally down-reservoir. Changes in phytoplankton biomass following the storm event were positively related to the down-reservoir DIP flux. In contrast, changes in phytoplankton biomass during stratification were negatively related to phytoplankton cell P quota and positively related to vertical transport of DOP, likely attributed to dominance by R. raciborskii and its capacity to metabolise luxury P storages and use organic P.
In using a novel combination of in situ, in vitro, and in silico techniques to derive phosphorus fluxes, alongside phytoplankton community data, this study has demonstrated that vertical fluxes of DIP and DOP into the surface waters of a subtropical lake are critical for promoting the dominance of bloom-forming cyanobacteria, including toxic R. raciborskii. Cyanobacteria and R. raciborskii in particular possess the ability to effectively utilise DIP and DOP from regeneration and transient fluxes from the hypolimnion through mechanisms such as high affinity P uptake and mineralization of DOP. These findings provide new insights into the P-related strategies used by cyanobacteria, and how they interact with physical and chemical processes to drive phytoplankton dominance in lakes. It has important implications for our scientific understanding of P processes in lakes and management of P-depauperate lakes, and raises important questions with respect to potential directions for future research.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Environment and Sc
Science, Environment, Engineering and Technology
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Rosser, S. M. Jane Horner. "Phytoplankton ecology in the upper Swan River estuary, Western Australia: with special reference to nitrogen uptake and microheterotroph grazing." Thesis, Curtin University, 2004. http://hdl.handle.net/20.500.11937/1562.
Full textAbstract:
Phytoplankton succession and abundance in estuaries is known to be influenced by the relative strengths of various seasonally changing physical and chemical factors. Previous studies of Swan River Estuary phytoplankton biomass and composition have identified salinity, temperature, rainfall and nutrients as the most important controlling factors. These conclusions are generally based on analysis of data from river length transects and depth integrated day-time sampling. They describe influences ,affecting whole system phytoplankton abundance and succession. Many of the typical seasonal bloom that develop are ephemeral and only extend over relatively small areas. The focus of this study is a single site, Ron Courtney Island, considered typical of the upper estuary region. This region of the estuary was chosen as representative of the section of river most influenced by allochthonous nutrient input. It has been the region of most frequent and intense algal blooms over the past decade. The factors, physical, biological or physiological, that have the greatest influence on controlling phytoplankton biomass under various ambient conditions for this system are determined. While previous studies have recognised the importance of nitrogen to phytoplankton growth in the Swan River Estuary, they have focused on NO;, with only anecdotal reference to the importance of the alternative nitrogen source, NH4+. This is the first study to explore the influence of different nitrogen source fluxes on phytoplankton biomass in the upper Swan River Estuary. The roles of physiological adaptation to, and preferences for, 'new' (NO,), recycled (NH4+) and organic (urea) nitrogen sources in relation to ambient nutrient levels are explored.Specific uptake rates (v), normalised to chlorophyll a, for NO;, NH4+ and urea were 0.2 ± 0.04 - 1831.1 ± 779.19, 0.5 ± 0.26 - 1731.6 ± 346.67 and 3.0 ± 0.60 - 2241.2 ± 252.56 ng N μg Chla-1 respectively. Urea concentration (14.8 - 117.7 μg urea-N 1-1) remained relatively constant over the 12 month study period. Measured ambient specific uptake rates for urea represent between 27.5% and 40.4% of total N uptake over the annual period February 1998 -January 1999. Seasonal nitrate uptake over the same period constituted only 11.3% (±10.77%, n=12) to 24.4% (± 13.02%, n=12) with the highest percentage during winter, when nitrate levels are elevated. It is suggested that urea provides a nutrient intermediary over the spring - summer period during transition from autotrophic to heterotrophic dominated communities. Grazing ,and nitrogen recycling are intricately connected by simultaneously providing top-down biomass control and bottom-up nutrient supply. Zooplankton (> 44 μm) grazing has been shown to reduce up to 40% of phytoplankton standing stock at times. Microheterotrophs (<300 pm) can reduce phytoplankton biomass production by up to 100% (potential production grazed, 11.1% day' - 99.6 % day-1) over an annual cycle. This correlated to mean seasonal day-time grazing loss of 80.47 ± 3.5 ngN μg Chla-1 in surface waters and 20.17 ± 9.7 ngN μg Chla-1 at depth (4.5m). Night time grazing for surface and bottom depths resulted in similar nitrogen loss rates (13.03 ± 4.84 ngN μg Chla-1).Uptake rates for nitrate (r2 0.501) and urea (r2 0.512), doing with temperature (r2 0.605) were shown to have the greatest influence on phytoplankton distribution over depth and time. This research emphasises the need for more detailed investigations into the physiology of nutrient uptake and the effects of nutrient fluxes on phytoplankton biomass and distribution. Further research into the roles of organic nitrogen and pico and nanoplankton in this system is recommended.
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Qin, Qubin. "Impacts of Physical Transport on Estuarine Phytoplankton Dynamics and Harmful Algal Blooms." W&M ScholarWorks, 2019. https://scholarworks.wm.edu/etd/1550153910.
Full textAbstract:
The spatial and temporal variability of phytoplankton biomass in estuaries is determined by both local processes and transport processes. Local processes include biological processes (e.g., photosynthesis, respiration/excretion, and grazing) and settling, whereas transport processes include advective and diffusive transports. Transport processes have been demonstrated to regulate phytoplankton dynamics significantly by distributing both phytoplankton and other dissolved and particulate substances (e.g., nutrients, salts, sediments, and chromophoric dissolved organic matter). Yet, these transport properties lack a framework that unifies the pieced description of their various effects, and quantification of their importance under various environmental conditions. This dissertation highlights the role of horizontal transport processes on phytoplankton dynamics in estuaries, including the initiation of harmful algal blooms (HABs). in Chapter 2, the flushing effect of transport processes and its interaction with local processes are exclusively examined, and its relative importance on the variability of phytoplankton biomass is quantified and compared to that of the local processes over timescales from hours to years, using an introduced concept of transport rate that can be numerically computed. in Chapter 3, a simple yet inclusive mathematical model is developed to examine the temporal and spatial variabilities in phytoplankton biomass in response to the various effects of physical transport, under nutrient and light limiting conditions. For estuaries whose dominant nutrient loading is from river input, three basic patterns are revealed for the relationships between phytoplankton biomass and flushing time under various environmental conditions. in Chapters 4 and 5, the flushing effect of transport processes on the initiation of harmful algal blooms (HABs) in estuaries is investigated, which is then applied to examine the location and timing of the initiation of an annual Cochlodinium (recently renamed Margalefidinium) polykrikoides bloom in the lower James River. Theoretical analysis shows that the flushing is the key factor that affects HAB initiation in multiple interconnected systems, and a relatively long period of time (weeks) is required for a successful bloom. A HAB tends to be observed first in locations with relatively long residence time, such as tributaries or areas with large eddies. Multiple unconnected originating locations can co-exist within an estuary that highly depends on hydrodynamics and salinity. A numerical module for C. polykrikoides bloom is developed and built into a 3D numerical model - EFDC, which considers the competitive advantages of C. polykrikoides such as mixotrophic growth, swimming, grazing suppression, and resting cyst germination. Numerical model results show that the flushing effect determines the origins of C. polykrikoides blooms in the lower James River, and the sub-tributary of Lafayette River, which is characterized by relatively long residence time, is favorable for the first bloom to occur, regardless of the cyst distribution. A further investigation of various environmental conditions for the C. polykrikoides bloom reveals that temperature and physical transport control the interannual variability in the timing of its initiation, and individual perturbations by southerly wind, heavy rainfall, and spring tide can cause strong flushing capable of interrupting, or even terminating, initiation of a HAB event in the lower James River.
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Rosser, S. M. Jane Horner. "Phytoplankton ecology in the upper Swan River estuary, Western Australia: with special reference to nitrogen uptake and microheterotroph grazing." Curtin University of Technology, Department of Environmental Biology, 2004. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=16266.
Full textAbstract:
Phytoplankton succession and abundance in estuaries is known to be influenced by the relative strengths of various seasonally changing physical and chemical factors. Previous studies of Swan River Estuary phytoplankton biomass and composition have identified salinity, temperature, rainfall and nutrients as the most important controlling factors. These conclusions are generally based on analysis of data from river length transects and depth integrated day-time sampling. They describe influences ,affecting whole system phytoplankton abundance and succession. Many of the typical seasonal bloom that develop are ephemeral and only extend over relatively small areas. The focus of this study is a single site, Ron Courtney Island, considered typical of the upper estuary region. This region of the estuary was chosen as representative of the section of river most influenced by allochthonous nutrient input. It has been the region of most frequent and intense algal blooms over the past decade. The factors, physical, biological or physiological, that have the greatest influence on controlling phytoplankton biomass under various ambient conditions for this system are determined. While previous studies have recognised the importance of nitrogen to phytoplankton growth in the Swan River Estuary, they have focused on NO;, with only anecdotal reference to the importance of the alternative nitrogen source, NH4+. This is the first study to explore the influence of different nitrogen source fluxes on phytoplankton biomass in the upper Swan River Estuary. The roles of physiological adaptation to, and preferences for, 'new' (NO,), recycled (NH4+) and organic (urea) nitrogen sources in relation to ambient nutrient levels are explored.Specific uptake rates (v), normalised to chlorophyll a, for NO;, NH4+ and urea were 0.2 ± 0.04 - 1831.1 ± 779.19, 0.5 ± 0.26 - 1731.6 ± 346.67 and 3.0 ± 0.60 - 2241.2 ± 252.56 ng N μg Chla-1 respectively. Urea concentration (14.8 - 117.7 μg urea-N 1-1) remained relatively constant over the 12 month study period. Measured ambient specific uptake rates for urea represent between 27.5% and 40.4% of total N uptake over the annual period February 1998 -January 1999. Seasonal nitrate uptake over the same period constituted only 11.3% (±10.77%, n=12) to 24.4% (± 13.02%, n=12) with the highest percentage during winter, when nitrate levels are elevated. It is suggested that urea provides a nutrient intermediary over the spring - summer period during transition from autotrophic to heterotrophic dominated communities. Grazing ,and nitrogen recycling are intricately connected by simultaneously providing top-down biomass control and bottom-up nutrient supply. Zooplankton (> 44 μm) grazing has been shown to reduce up to 40% of phytoplankton standing stock at times. Microheterotrophs (<300 pm) can reduce phytoplankton biomass production by up to 100% (potential production grazed, 11.1% day' - 99.6 % day-1) over an annual cycle. This correlated to mean seasonal day-time grazing loss of 80.47 ± 3.5 ngN μg Chla-1 in surface waters and 20.17 ± 9.7 ngN μg Chla-1 at depth (4.5m). Night time grazing for surface and bottom depths resulted in similar nitrogen loss rates (13.03 ± 4.84 ngN μg Chla-1).
Uptake rates for nitrate (r2 0.501) and urea (r2 0.512), doing with temperature (r2 0.605) were shown to have the greatest influence on phytoplankton distribution over depth and time. This research emphasises the need for more detailed investigations into the physiology of nutrient uptake and the effects of nutrient fluxes on phytoplankton biomass and distribution. Further research into the roles of organic nitrogen and pico and nanoplankton in this system is recommended.
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Brown, Penelope Cranstoun. "The development and decline of phytoplankton blooms in the southern Benguela upwelling region." Thesis, University of Cape Town, 1987. http://hdl.handle.net/11427/23178.
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Nascimento, Francisco J. A. "Trophic ecology of meiofauna response to sedimentation of phytoplankton blooms in the Baltic Sea /." Doctoral thesis, Stockholm : Department of Systems Ecology, Stockholm University, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-38809.
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Diss. (sammanfattning) Stockholm : Stockholms universitet, 2010.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript. Paper 5: In press.
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Fahal, Iman Hassan. "Phytoplankton blooms and fish larvae off the Northumberland Coast during the period 1992-1994." Thesis, University of Newcastle Upon Tyne, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389569.
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Merrick, Chester John. "Phytoplankton-zooplankton interactions in Mt. Bold Reservoir, South Australia /." Title page, contents and summary only, 1990. http://web4.library.adelaide.edu.au/theses/09PH/09phm568.pdf.
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