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1
Clegg, Mark Robert. "Behavioural ecology of freshwater phytoplanktonic flagellates." Thesis, Lancaster University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.403729.
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Österling, Martin. "Ecology of freshwater mussels in disturbed environments." Doctoral thesis, Karlstad University, Faculty of Social and Life Sciences, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-734.
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The number of species extinctions is increasing at an alarming rate. Long-lived freshwater mussels of the order Unionoida, which include a parasitic stage on a host fish, are highly threatened. Habitat degradation by turbidity and sedimentation is thought to be one major reason for their decline. The objective of this thesis was to examine recruitment patterns and identify the causes of the lack of recruitment in the threatened unionoid freshwater pearl mussel (Margaritifera margaritifera). In addition, I investigated the effects of turbidity on non-endangered dreissenid mussels, where turbidity was manipulated through use of bioturbating mayflies.
In a survey of 107 Swedish streams, mussel population size and trout density were both positively correlated to recruitment probability of M. margaritifera. A more in-depth study of the age-structure of nine populations revealed that four of these populations showed no signs of recruitment over the last ten years. Within-stream variation in recruitment was high as both mussels and trout had patchy distribution, and may be important for population regulation. Moreover, examination of different life stages revealed no differences in the gravid mussel stage or the stage when mussels infect salmonid fish. Instead, differences were observed for the juvenile, benthic stage, presumably related to differences in turbidity and sedimentation. High turbidity may affect filter-feeding efficiency of mussels and high sedimentation may reduce survival by clogging sediments, thereby altering, for example, oxygen and food conditions. In the study of the effects of turbidity, bioturbating mayflies increased turbidity and filter-feeding dreissenid mussels reduced turbidity. Mussel growth both decreased and increased with increasing turbidity, depending on sediment type.
Turbidity and sedimentation often impact entire stream systems, and a holistic, catchment-based management strategy may be needed to reduce the effects of sedimentation on freshwater pearl mussels. The effects of restoration take a long time and must start soon if recruitment of mussels is to be re-established. Restoration may also be more urgent in some streams than in others, as the maximum age of M. margaritifera populations in my study differed by as much as 60 years. As mussel and trout densities seem to be important for recruitment success, one conservation method may be to concentrate mussels into sites where trout density is high.
3
Chadderton, W. L. "The ecology of Stewart Island freshwater communities." Thesis, University of Canterbury. Zoology, 1990. http://hdl.handle.net/10092/6568.
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A comprehensive survey of the stream and river faunas of Stewart Island (invertebrates and fish) was undertaken between August 1987 and December 1989. In total, 113 invertebrate taxa and 12 fish species were recorded. The invertebrate fauna is characterised by a common core of taxa (Chiltonia rivertonensis, Oligochaeta, Chironomidae, Deleatidium, Zelandoperla, Zelandobius, Austroperla cyrene, Hydrobiosidae stenocerca, Hydrobiosidae, Simuliidae, and Scirtidae) and a paucity or absence of some common mainland families or genera, notably the Notonemouridae, Conoesucidae, and Archichauliodes. The fish fauna consists of diadromous species except for Galaxias vulgaris. A number of invertebrate and fish species are more widespread, or abundant, and occupy more diverse habitat types than reported in mainland studies. They include the isopod Austridotea benhami, and the fishes Galaxias argenteus, G. fasciatus and Gobiomorphus huttoni. These differences may reflect the more pristine conditions of Stewart Island streams and an absence of predatory salmonids on the island.
Gut analysis of G. huttoni and G. fasciatus confirmed that they fed predominantly on benthic invertebrates and terrestrial prey items, respectively. Both species appeared to be opportunistic feeders and showed a low degree of prey selectivity.
Experimental studies at six sites in the Rakeahua River system indicated that leaf litter breakdown (kamahi leaves) rates were rapid at headwater sites where feeding by shredders (principally Austroperla cyrene) was high. In contrast, breakdown rates were slower at mainstem sites even though the large detritivore/carnivore, Austridotea benhami was present.
In summary, the Stewart Island freshwater fauna can be seen to possess a number of distinctive features, but the extent of these appear to be no greater than those found between the North and South Islands of New Zealand. Stewart Island is unique, however, because of the apparent absence of adventive species, including trout, that are common on the mainland. Because of this and the largely pristine nature of its catchments, I suggest that greater protection should be afforded to the island's freshwater systems than is imparted by Reserve and Conservation Land status.
4
Sivichai, Somsak. "Tropical freshwater fungi : their taxonomy and ecology." Thesis, University of Portsmouth, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302240.
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Sanderson, Rory J. "Ecology of freshwater plankton in contrasting hydraulic environments." Thesis, University of Leicester, 1998. http://hdl.handle.net/2381/29785.
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The effects of contrasting water residence time on the planktonic community of three water bodies was studied. The sites were Rutland Water, Covenham reservoir and the River Nene, in order of decreasing retention time. The river was the only site where the residence time was sufficiently short to directly impact upon planktonic populations. The importance of physical mechanisms of control in the river was indicated by the dominance of r-selected phytoplankton, namely diatoms and green algae, and zooplankton, namely rotifers. This pattern was in contrast to that of the reservoirs in which slower-growing cyanobacteria and cladocerans dominated. Riverine rotifers were found to have rapid population turnover, due to a combination of short pre-adult duration and high maximum growth rates. Some species also showed a shift in reproductive behaviour to the constant production of resting eggs. This was assumed to convey benefits in a system where resting stages may be less susceptible than adults to downstream displacements. The total chlorophyll 'a' concentration achieved per unit phosphorus was significantly lower in the river than either of the reservoirs. Algal density was negatively associated with discharge in the Nene, suggesting the importance of physical control. The relationship was not a simple one, however, as periods of increased retention time during the summer were associated with low algal density. The absolute density of rotifers was found to be constrained by discharge. Animals were rare above a threshold flow velocity of 0.08ms-1. Simple models of water flow in open channels were insufficient to account for the continued persistence of a plankton in the Nene given the level of advection. It was assumed that the overall retention time of the system was increased by the presence of dead zones within the channel which 'held' planktonic organisms for sufficient time for populations to develop. This behaviour was important during the spring when population density increased in the main channel.
6
Lee, Jacqueline S. "The distribution and ecology of the freshwater molluscs of northern British Columbia." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0033/MQ62481.pdf.
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Jamal, Al-Lail S. S. "Ecophysiological studies on freshwater gammarid crustaceans." Thesis, University of Nottingham, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373334.
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Fear, Lesley Anne. "Microbial ecology of the gut of Gammarus pulex." Thesis, Lancaster University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250026.
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Roznere, Ieva. "Health assessment of freshwater mussels using metabolomics." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1461065547.
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Barretto, de Menezes Alexandre. "Molecular ecology of cellulose-degrading microorganisms in freshwater lakes." Thesis, University of Liverpool, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.511074.
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11
Cai, Ji. "Ecology and diversity of freshwater picocyanobacteria in Japanese lakes." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263502.
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12
Zhu, Bin. "Direct and indirect ecological effects of Dreissenid mussels (the zebra mussel Dreissena polymorpha and the quagga mussel D. bugensis) on submerged macrophytes in North American lakes." Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2006. http://proquest.umi.com/login?COPT=REJTPTU0NWQmSU5UPTAmVkVSPTI=&clientId=3739.
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Huddleston, Amara Lynn. "The Influence of Ice Cover on the Coupling between Lake Erie Larval Walleye and their Prey." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1532082401065932.
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14
DeVaul, Sarah Bess. "Mixotrophy in Freshwater Foodwebs." Diss., Temple University Libraries, 2016. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/380959.
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BiologyPh.D.
Environmental heterogeneity in both space and time has significant repercussions for community structure and ecosystem processes. Dimictic lakes provide examples of vertically structured ecosystems that oscillate between stable and mixed thermal layers on a seasonal basis. Vertical patterns in abiotic conditions vary during both states, but with differing degrees of variation. For example, during summer thermal stratification there is high spatial heterogeneity in temperature, nutrients, dissolved oxygen and photosynthetically active radiation. The breakdown of stratification and subsequent mixing of the water column in fall greatly reduces the stability of the water column to a vertical gradient in light. Nutrients and biomass that were otherwise constrained to the depths are also suspended, leading to a boom in productivity. Freshwater lakes are teeming with microbial diversity that responds to the dynamic environment in a seemingly predictable manner. Although such patterns have been well studied for nanoplanktonic phototrophic and heterotrophic populations, less work has been done to integrate the influence of mixotrophic nutrition to the protistan assemblage. Phagotrophy by phytoplankton increases the complexity of nutrient and energy flow due to their dual functioning as producers and consumers. The role of mixotrophs in freshwater planktonic communities also varies depending on the relative balance between taxon-specific utilization of carbon and energy sources that ranges widely between phototrophy and heterotrophy. Therefore, the role of mixotrophy in the microbial food web is difficult to predict because functional types of mixotrophs along a gradient of nutritional strategies contribute differently to nutrient cycling and carbon sequestration. The overall objective of this work was to advance existing knowledge of the abundance and activity of phagotrophy phytoplankton in lacustrine systems. The incorporation of mixotrophy into the microbial food web requires the complement of physiological studies in culture (as described in chapter 2) and quantification of activity (including abundance and bacterivory) in relation to strict phototrophs and heterotrophs in situ (as described in chapter 3 and 4). Information on the physiological ecology of mixotrophic protists is crucial to understanding their role in planktonic food webs and influence on the dynamic microbial community structure in lake ecosystems. An understanding of the ecological functioning of lakes has ultimate consequences for management of water resources, particularly in the face of global climate change.
Temple University--Theses
15
Rodrigues, JoÃo FabrÃcio Mota. "How the freshwater turtles survive and reproduce in caatinga? - Life history traits of Phrynops tuberosus (Testudines: Chelidae)." Universidade Federal do CearÃ, 2013. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=9486.
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The life history theory studies the characteristics combinations that maximize the organisms reproduction and survival in the environment where they live. The species
use the habitat in a diverse way and this use depends on the environmental conditions in the available habitats. Phrynops tuberosus, a freshwater turtle found in the north-northeastern regions of Brazil, is the animal-model chosen for the life history traits and habitat use studies. This work aims understand how this species reproduce, maintain and use the habitat in Caatinga. The study generated biological and ecological knowledge of the species and allowed the testing of hypotheses and predictions of life history traits, sexual dimorphism and habitat use. Selection of clutching sites, males smaller than females and preference of larger animals for environments most exposed were found in the populations studied. The results facilitate understanding of reproduction and survival of turtles in a semiarid environment.A teoria de histÃria de vida estuda as combinaÃÃes de caracterÃsticas que maximizam a reproduÃÃo e a sobrevivÃncia dos organismos no ambiente onde vivem. As espÃcies utilizam o ambiente de modo diverso, e esse uso depende das condiÃÃes existentes nos hÃbitats disponÃveis. Phrynops tuberosus, cÃgado encontrado nas regiÃes norte-nordeste do Brasil, Ã o animal-modelo escolhido para o estudo dos traÃos de histÃria de vida e de uso de hÃbitat. Esse trabalho objetiva entender como a espÃcie se reproduz, organiza-se e utiliza o hÃbitat na caatinga. O estudo gerou conhecimentos biolÃgicos e ecolÃgicos da espÃcie e permitiu o teste de hipÃteses e previsÃes sobre traÃos de histÃria de vida, dimorfismo sexual e uso de hÃbitat. SeleÃÃo de locais de desova, machos menores que fÃmeas e preferÃncia de animais maiores por ambientes mais expostos foram encontradas nas populaÃÃes estudadas. Os resultados encontrados facilitam a compreensÃo da reproduÃÃo e da sobrevivÃncia dos quelÃnios em um ambiente do semiÃrido.
16
Qin, Peibing. "Effects of light, nutrients and Dreissena (Dreissena polymorpha and Dreissena bugensis) on benthic ecosystems in lakes." Related electronic resource:, 2007. http://proquest.umi.com/pqdweb?did=1407689711&sid=1&Fmt=2&clientId=3739&RQT=309&VName=PQD.
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Amin, M. K. A. "The ecology and genetics of Pseudomonas bacteriophage in freshwater systems." Thesis, Cardiff University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381224.
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Lassiere, Olivia L. "The ecology of Neoechinorhynchus rutili (Acanthocephala) in Scottish freshwater lochs." Thesis, University of Glasgow, 1989. http://theses.gla.ac.uk/2440/.
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1. The ecology of Neoechinorhynchus rutili (Acanthocephala) has been investigated in a Scottish population of brown trout (Salmo trutta) inhabiting a small highland loch, in Central region. The results have been compared with data from other hosts and localities. In addition, a complementary study on the ecology of Echinorhynchus truttae in brown trout was carried out at a reservoir in Lothian Region. 2. A review of the knowledge of the classification, morphology of developmental stages, life cycle, ecology and distribution and biochemistry and physiology of Neoechinorhynchus rutili was undertaken. 3. Examination of 1189 fish (11 species) from 8 Scottish regions and collation of available records indicated that Neoechinorhynchus rutili infects 8 species of freshwater fish (Esox lucius, Gasterosteus aculeatus, Perca fluviatilis, Phoxinus phoxinus, Salmo gairdneri, Salmo salar, Salmo trutta and Salvelinus alpinus) at 41 sites in 6 Scottish regions. These sites encompass a wide spectrum of aquatic environments in terms of size, water quality and faunal community structure. This wide distribution of Neoechinorhynchus rutili is explained through the multifarious habits of the definitive host species and possibly interactions with human, avian or insect factors. There is evidence for temporal stability of the infection at some of these sites. 4. The main field site for the examination of the ecology of Neoechinorhynchus rutili was Loch Maragan (Grid ref. NN 402278), Central Region. This small loch (surface area 7.3 ha, maximum depth 10.2 m, volume 153943 m3) lies at 472 m above sea level and had slightly acid water conditions (p.H. 6.44, October 1986.) Three species of fish (Anguilla anguilla, Phoxinus phoxinus and Salmo trutta) were found to inhabit the loch. In August 1987 the brown trout population size was estimated, by a simple mark and recapture technique, as 2641 (1 to 3 years olds) (Maximum value). 5. Two benthic faunal surveys, carried out in November 1986 and May 1987 respectively, did not reveal the species of invertebrate which was acting as intermediate host for Neoechinorhynchus rutili at Loch Maragan. 6. A total of 226, between 1 and 5 years old were caught at Loch Maragan over a 25 month period between July 1986 and August 1988 and examined for visceral and gut macroparasites. Minnows (n = 207) and alder flies (Sialis lutaria) (larvae and adults) were also examined. Sialis lutaria larvae were infected with Neoechinorhynchus rutili and unidentified trematode metacercaria. The minnows harboured Neoechinorhynchus rutili, Ligula intestinalis and Crepidostomum spp. The brown trout harboured Capillaria salvelini, Crepidostomum spp., Diphyllobothrium ditremum and D.dendriticum and Neoechinorhynchus rutili. The distributions of these parasitic infections amongst their hosts are described. 7. The collection of 4992 Neoechinorhynchus rutili from 226 brown trout, revealed the overdispersed nature of the infection (k = 0.7893), individual fish harbouring between 1 and 324 worms. The overall prevalence and mean intensity of infection were 87.6% and 21.5 respectively. Monthly prevalence values (of samples) never fell below 50%. Trout age, but not sex, influenced the infection parameters. 8. Neoechinorhynchus rutili exhibited a definite seasonal cycle of intensity and maturation in brown trout at Loch Maragan. Although recruitment apparently occurred throughout the year, worm intensitites, particularly of gravid females, peaked in summer when water temperatures and host feeding rates were maximal. Acanthor production occurred between March and November. In summer 1987 the Neoechinorhynchus rutili metapopulation (in trout aged 1 to 3 years) was estimated to be 36154, of which 5566 were gravid females. These females were estimated to have produced 1.6 x 108 shelled acanthors which represents a reproductive success rate of 3.5 x 10-3 % i.e. 1 in 38030 shelled acanthors becoming a reproductively active female in the next parasite generation. No evidence for density dependent effects upon worm fecundity were found. Similar seasonal patterns were found at other Scottish locations. 9. Neoechinorhynchus rutili was typically found in the ileas and rectal regions of the trout gut, but the distribution was dynamic with respect to season, worm sex, state of maturity and infection intensity. 10. No adverse effect upon the condition factor of brown trout in Loch Maragan could be attributed to the presence of Neoechinorhynchus rutili. 11. The diet of brown trout at Loch Maragan was analysed and Sialis lutaria larvae formed an important element, especially in spring. Larger trout were found to be piscivorous. 12. Acanthocephalan specimens found in the haemocoel of Sialis lutaria larvae collected from 2 Scottish sites (Loch Maragan and Loch Monzievaird) were identified, on the basis of their morphology, as the eoacanthocephalan Neoechinorhynchus rutili. 13. Sialis lutaria larvae were found to be infected with Neoechinorhynchus rutili at Loch Maragan and 3 other Scottish sites where fish were also infected (Bridge of Weir fish farm, Drumore Loch and Loch Monzievaird). The distribution of infection was typically overdispersed (k values ranged from 0.27 to 1.25). Overall prevalence values ranged from 4.2 to 40.7%. Infection parameters varied with insect size and season. 14. Establishment of Neoechinorhynchus rutili in experimental infections of rainbow trout (Salmo gairdneri) via feeding upon infected Sialis lutaria larvae was up to 33% successful. Experiments to infect ostracods (Herpetocypris reptans) and Sialis lutaria larvae via feeding with shelled acanthors were unsuccessful. 15. Postcyclic transmission of Neoechinorhynchus rutili occurred in the laboratory when rainbow trout were exposed to worms established in the three-spined stickleback (Gasterosteus aculeatus) hosts. The re-establishment rate was estimated as 92.8%. There is circumstantial evidence to suggest that this form of transmission occurs in natural populations in Scotland. 16. In the complementary study at Gladhouse Reservoir, 4 visceral and gut parasites were identified in the brown trout: Cystidicola farionis, Eustrongylides sp. (Nematoda), Eubothrium crassum (Cestoda) and Echinorhynchus truttae (Acanthocephala). Both E.crassum and Echinorhynchus truttae were overdispersed in their hosts and the overall prevalences and intensities of infection were 61.9% and 92.9% and 1.48 and 156.4 respectively. Echinorhynchus truttae exhibited a seasonal pattern of maturation, females releasing shelled acanthors in the summer months. This study also considered the logistics of carrying out scientific research in collaboration with members of the public.
19
Harrison, A. J. "Ecology and control of the freshwater fish louse (Argulus foliaceus)." Thesis, Queen's University Belfast, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.431598.
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Thomas, Gethin Rhys. "Conservation ecology of the endangered freshwater pearl mussel, Margaritifera margaritifera." Thesis, Swansea University, 2011. https://cronfa.swan.ac.uk/Record/cronfa43091.
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The general aim of this thesis was to examine the merits of ex-situ vs. in-situ strategies for the conservation of the endangered freshwater pearl mussel, Margaritifera margaritifera, and to investigate the relationship of the larval parasitic stages of the mussel (glochidia) with the salmonid hosts. To this end, I critically reviewed the literature on conservation of freshwater mussels, developed methods for quantifying the behaviour and activity patterns of adult mussels in captivity, experimentally studied host specificity, and quantified the physiological and behavioural effects of glochidia upon salmonid hosts. The results indicate that the conservation of the freshwater pearl mussel is probably best addressed at the watershed scale, and will benefit from a combination of ex-situ and in-situ techniques, as well as from a more critical assessment of findings, many of which are only reported in the grey literature. Empirical, peer-reviewed data are badly needed to inform current conservation efforts. Novel Hall-effect magnetic sensors were used to quantify and characterise discrete mussel behaviours without adversely affecting the welfare or survival of adult mussels, and these hold considerable potential for determining optimal rearing conditions for ex-situ conservation. Arctic charr was shown to be a potentially suitable host for M. margaritifera, and occupied an intermediate position in host suitability between brown trout and Atlantic salmon. Physiological impacts of glochidia upon brown trout included swelling of secondary lamellae and spleen enlargement, but the latter tended to be slight and was restricted to 1 month post-exposure. Glochidia encystment had no significant effect on blood haematocrit, respiratory performance, or cryptic colouration of brown trout hosts. The behavioural effects were more subtle and glochidiosis made brown trout more risk-averse and less willing to explore a novel habitat, without affecting the host's ability to chemically recognise and avoid cues from a predator. Overall, the results of this thesis indicate that the impacts of glochidia upon salmonid hosts are probably slight and temporally variable, and may perhaps lead to increased host survival, which would support the symbiosis-protocooperation theory of glochidia-salmonid interaction.
21
Indranil, Mukherjee. "Ecology of kinetoplastid flagellates in freshwater deep lakes of Japan." 京都大学 (Kyoto University), 2016. http://hdl.handle.net/2433/217135.
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Schmidt, Brian A. "Determining the Habitat Limitations of Maumee River Walleye Production to Western Lake Erie Fish Stocks." University of Toledo / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1463067261.
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Medeiros, Elvio S. F. "Trophic ecology and energy sources for fish on the floodplain of a regulated dryland river Macintyre River, Australia /." Connect to this title online, 2004. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20051115.174552/.
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Neubauer, Scott C. "Carbon dynamics in a tidal freshwater marsh." W&M ScholarWorks, 2000. https://scholarworks.wm.edu/etd/1539616793.
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The sources and fates of carbon in a tidal freshwater marsh (Sweet Hall marsh; Pamunkey River, Virginia) were determined to understand the role that these marshes play with respect to estuarine carbon cycling. A carbon gas flux model, based on measured carbon dioxide and methane fluxes, was developed to calculate annual rates of macrophyte and microalgal photosynthesis and community and belowground respiration. Because carbon fluxes out of marsh sediments may underestimate true belowground respiration if sediment-produced gases are transported through plant tissues, gross nitrogen mineralization was used as a proxy for belowground carbon respiration. Annual community respiration exceeded gross photosynthesis, suggesting an allochthonous input of organic carbon to the marsh. Sediment deposition during tidal flooding was measured as a potential exogenous carbon source. Short term deposition rates (biweekly to monthly) were spatially and temporally variable, with highest rates measured near a tidal creek during summer. Annual deposition on the marsh was sufficient to balance relative sea level rise and measured respiration rates. Sediment inventories of 7Be indicated that spatial patterns of sedimentation were not due to sediment redistribution within the marsh. Accretion rates calculated from 137Cs (decadal scale) and 14C (centuries to millennia) were substantially less than annual deposition rates. The concentration and isotopic composition of dissolved and particulate inorganic and organic carbon (DIC, DOC, POC) were measured in a marsh creek which drained the study site. Seasonal isotopic variations in DIC were explained by marsh porewater drainage and decomposition of marsh-derived carbon. A model linking DIC concentrations and water transport showed that DIC export from tidal marshes could explain a significant portion of excess DIC production in the adjacent estuary. Isotopic mixing models indicated seasonal variability in the importance of phytoplankton as a source of DOC and POC although there was no evidence for a net flux of these materials between the marsh and estuary. Annually, the marsh carbon budget was closely balanced, with sources exceeding sinks by approximately 5 percent. This similarity suggests that those processes which were not quantified (e.g. consumption by marsh and riverine fauna) were quantitatively unimportant with respect to the entire marsh carbon budget.
25
Deweber, Jefferson Tyrell. "Background studies on the fishes of the Opossum Creek / Camp Hydaway Lake system and effects of an herbicide on the lake's aquatic plants /." Lynchburg, VA : Liberty University, 2007. http://digitalcommons.liberty.edu.
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Johnson, Virginia L. "Primary productivity by phytoplankton : temporal, spatial and tidal variability in two North Carolina tidal creeks /." Electronic version (PDF), 2005. http://dl.uncw.edu/etd/2005/johnsonv/virginiajohnson.pdf.
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Judge, David, and n/a. "The Ecology of the polytopic freshwater turtle species, Emydura macquarii macquarii." University of Canberra. Resource, Environmental and Heritage Sciences, 2001. http://erl.canberra.edu.au./public/adt-AUC20050418.151350.
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An ecological study of Emydura macquarii macquarii in the south-east region
of Australia was conducted between October 1995 and March 1998. E. m. macquarii is
an abundant and widespread species of short-necked turtle that is highly variable in
morphology and related life history attributes. No study in Australia had previously
looked at geographic variation in biological traits in freshwater turtles, hence the level
of variation in E. m. macquarii had been poorly documented. The principal aims of this
study were to investigate the plasticity of life history traits across populations of E. m.
macquarii and to speculate on possible causes. A more intensive study was also
conducted on a rare and suspected declining population of E. m. macquarii in the
Nepean River to determine whether relevant management and conservation measures;
were required.
The study involved comparing various life history attributes between five
populations of E. m. macquarii (Brisbane River, Macleay River, Hunter River, Nepean
River and Murray River). The populations were specifically chosen to account for the
range of variation in body size within this subspecies. Body size (maximum size, size at
maturity, growth rates), population structures (sex ratios, age and size structures),
reproductive traits (clutch mass, clutch size, egg size, egg content, etc.) and other
attributes were collected for each population. Patterns of life history traits, both within
and among populations, were explored so that causes of variation could be sought.
Geographic variation in Body Size and other Related Life History Traits
Body size in E. m. macquarii differed markedly between populations. Females
ranged in maximum sizes (carapace length) of 180 mm in the Macleay River to over
300 mm in the Murray River. E. m. macquarii was sexually dimorphic across all
populations with females larger than males in all cases. Maximum body size was
positively related to the size at which a turtle matures. The size at maturity in turn was
positively related to juvenile growth rates. Age was a more important factor for males
in terms of timing of maturity whereas in females it was body size. Morphological
variation was not only great between populations, but also within populations.
Maximum body size was unrelated to latitude; hence it was inferred that habitat
productivity had the most important influence on geographic variation in body size.
Population structures also differed between populations. Sex ratios did not differ in the
Brisbane, Macleay and Murray Rivers. However, a male bias was present in the Nepean
River population and a female bias in the Hunter River. Juveniles were scarce in the
Brisbane and Macleay Rivers but numerous in the Nepean and Hunter Rivers.
Geographic Variation in Reproduction
There was large variation in reproductive traits across populations of E. m.
macquarii. Nesting season began as early as mid-September in the Brisbane River and
as late as December in the Hunter River, and continued until early January. Populations
in the Hunter and Murray Rivers are likely to produce only one clutch per season while
populations from the Macleay and Nepean Rivers can produce two, and on some
occasions, three clutches annually. The majority of females would appear to reproduce
every year.
Clutch mass, clutch size, and egg size varied greatly both within and among
populations. A large proportion of variation in reproductive traits was due to the effects
of body size. E. m. macquarii from large-bodied populations such as in the Brisbane
and Murray Rivers produced bigger eggs than small-bodied populations. Within a
population, clutch mass, clutch size, and egg size were all correlated with body size,
except the Nepean River. The variability of egg size was smaller in large-bodied
populations where egg size was more constant.
Not all variation in reproductive traits was due to body size. Some of this
variation was due to annual differences within a population. Reproductive traits within
a population are relatively plastic, most likely a result of changing environmental
conditions. Another source is the trade-off between egg size and clutch size. A negative
relationship was found between egg size and clutch size (except the Brisbane River).
Reproductive variation was also influenced by latitudinal effects. Turtles at lower
latitudes produces more clutches, relatively smaller clutch sizes, clutch mass and larger
eggs than populations at higher latitudes. Annual reproductive output is greater in
tropical populations because they can produce more clutches per year in an extended
breeding season.
Eggs that were incubated at warmer temperatures hatched faster and produced
smaller hatchlings. Incubation temperatures above 30�C increased egg mortality and
hatchling deformities, suggesting this is above the optimum developmental temperature
for E. m. macquarii. Hatchling size was positively related to egg size, hence hatchling
sizes was on average larger in the Murray and Brisbane rivers. However, population
differences remained in hatchling size after adjustments were made for egg size. For
example, hatchlings from the Hunter River were smaller than those from the Macleay
River despite the egg size being the same. These differences were most likely due to the
shorter incubation periods of hatchlings from the Hunter River.
Nepean River
The Nepean River population of E. m. macquarii is at the southern coastal limit
of its range. This is a locally rare population, which is believed to be declining. This
study aimed at determining the distribution, abundance, and population dynamics to
assess whether any conservation management actions were required. E. m. macquarii in
the Nepean River was mainly concentrated between Penrith and Nortons Basin,
although even here it was found at a very low density (10.6 - 12.1 per hectare). The
largest male caught was 227 mm while the largest female was 260.4 mm. Males
generally mature between 140 - 150 mm in carapace length and at four or five years of
age. Females mature at 185 -195 mm and at six to seven years of age.
Compared with other populations of E. macquarii, Nepean River turtles grow
rapidly, mature quickly, are dominated by juveniles, have a male bias and have a high
reproductive output. Far from being a population on the decline, the life history traits
suggest a population that is young and expanding. There are considered to be two
possible scenarios as to why the Nepean River population is at such a low density when it appears to be thriving. The first scenario is that the distribution of the population on
the edge of its range may mean that a small and fluctuating population size may be a
natural feature due to sub-optimal environmental conditions. A second scenario is that
the population in the Nepean River has only recently become established from dumped
pet turtles.
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Hastie, Lee Clark. "Conservation and ecology of the freshwater pearl mussel (Magaritifera margaritifera (L.))." Thesis, University of Aberdeen, 1999. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=158482.
Full textAbstract:
The population, reproductive biology and physical habitat requirements of endangered freshwater pearl mussel (Margaritifera margaritifera (L.)) populations in Scotland were investigated. Surveys of viable populations revealed overall densities, based on 1m2 quadrat counts, of 0.27-7.98 mussels.m-2. Total estimates for rivers, based on extrapolations of 50m transect counts, ranged from 2,000 to 0.9-3.7 million mussels. The expected predominance of young mussels was not achieved in any population. In order to test a hypothesis that juveniles were under-represented in samples, six populations first studied in 1984/85 were re-investigated in 1996/97. The relative numbers of 11-20y old individuals found in 1996/7 were consistently larger than those of 1-10y olds found a decade earlier. This provides strong evidence of sampling bias. M.margaritifera grow in an approximately asymptotic fashion and the von Bertalanffy equation is an appropriate descriptor. Growth may be influenced by temperature. In general, large mussels grow in large, cold rivers and vice versa; although there are exceptions, which suggest that additional factors may be involved. The timing of annual reproduction seems to be related to temperature. Mussels in the warmest rivers tend to spawn earliest. The prevalence and magnitude of natural parasitic mussel larval (glochidial) infections in wild salmon (Salmo salar L.) and trout (S.trutta L.) stocks were comparable to those reported elsewhere. Older fish seem to be less susceptible to glochidiosis than 0+ fish. Some trout stocks appear to be under-utilised by M.margaritifera, possibly due to differences in behaviour and/or place of origin. River bed substratum characteristics appear to be the best physical parameters for describing M.margaritifera habitat. Boulder-stabilised refugia, which contain enough sand/gravel for borrowing, are ideal habitats for juveniles.
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Clarke, Hazel Caroline. "Ecology and behaviour of the invasive freshwater amphipod gammarus pulex (L.)." Thesis, Queen's University Belfast, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.601109.
Full textAbstract:
The sucess of invasive species is said to depend upon the availability of resources, interactions with natural enemies and the abiotic environment. However, the behavioural interactions also play an important role. This thesis uses the freshwater amphipod Gammarus pulex (L.) to investigate the ecology and behaviour of an invasive species, with particular emphasis on female reproduction.
30
Hijji, A. M. "Studies on the pollution ecology of the freshwater isopod Asellus aquaticus." Thesis, University of Nottingham, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374807.
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Hill, Samantha. "The ecology and conservation of the rare freshwater bryozoan, Lophopus crystallinus." Thesis, University of Reading, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.434311.
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Atkinson, Benjamin K. "Community ecology of creek-dwelling freshwater turtles at Nokuse Plantation, Florida." [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0025093.
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Schuwerack, Petra-Manuela. "Environmental pollution and disease : multiple stress responses in freshwater hosts." Thesis, Royal Holloway, University of London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272253.
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Babiker, Ismail Elsheikh. "Evaluation of various biomanipulations aimed at controlling freshwater pulmonate snails." Thesis, University of Sussex, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.332587.
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Tokeshi, M. "The population and community ecology of chironomids in a small temperate stream." Thesis, University of East Anglia, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355362.
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Harlin, Hugo. "2D Modelling of Phytoplankton Dynamics in Freshwater Lakes." Thesis, Uppsala universitet, Avdelningen för beräkningsvetenskap, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-388868.
Full textAbstract:
Phytoplankton are single celled organisms capable of phytosynthesis, and are present in all the major oceans and lakes in the world. Phytoplankton contribute to 50% of the total primary production on Earth, and are the dominating primary producer in most aquatic ecosystems. This thesis is based on the 1D deterministic model by Jäger et. al. (2010) which models phytoplankton dynamics in freshwater lakes, where phytoplankton growth is limited by the availability of light and phosphorus. The original model is here extended to two dimensions to include a horizontal dimension as well as a vertical dimension, in order to simulate phytoplankton dynamics under varying lake bottom topographies. The model was solved numerically using a grid transform and a finite volume method in MATLAB. Using the same parameter settings as the 1D case studied by Jäger et. al. (2010), an initial study of plankton dynamics was done by varying the horizontal and vertical diffusion coefficients independently.
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Stott, Philip. "Terrestrial movements of the freshwater tortoise Chelodina longicollis." Title page, contents and summary only, 1988. http://web4.library.adelaide.edu.au/theses/09SM/09sms888.pdf.
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Cowley, C. "The influence of road runoff on the benthic macro-invertebrates of an unpolluted chalk stream." Thesis, University of Westminster, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.354965.
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Clark, Ezra. "Microthermal habitats in British rivers." Thesis, University of Exeter, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267237.
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Suttle, Curtis Arnold. "Effects of nutrient patchiness and N:P supply ratios on the ecology and physiology of freshwater phytoplankton." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/27547.
Full textAbstract:
Laboratory and field experiments examined several aspects of the interaction of freshwater phytoplankton species and plankton communities with nitrogen and phosphorus nutrient resources. The laboratory studies focused on the following three main areas: 1) effects of nutrient 'patchiness' on phytoplankton community structure; 2) kinetics of phosphate (PO₄⁻³ ) and ammonium (NH₄⁺) uptake of phytoplankton grown under non-steady-state but limiting rates of nutrient supply; 3) the effect of different N:P supply ratios on phytoplankton NH₄⁺ and PO₄⁻³ uptake kinetics and community structure. Nutrient 'patchiness' was simulated by altering the frequency of nutrient addition to cultures. Under conditions of infrequent addition (once per 18 days) dominance shifted to a larger species, and the average cell size of another species increased. Observations of PO₄⁻³ uptake kinetics were not consistent with most other studies where kinetics were determined under steady-state conditions. With respect to PO₄⁻³, the duration over which maximum uptake rates were sustained was species specific. There was a short lag before maximum uptake rates were realized, and whether maximum uptake rates occurred at the lowest or at intermediate dilution rates depended on the time scale over which the uptake measurements were made. NH₄⁺ uptake rates were found to be greatly enhanced during the first few minutes of uptake. When natural plankton assemblages were grown under N:P supply ratios of 5:1, 15:1 and 45:1 (by atoms), the treatments selected for different competitive dominants. An N:P ratio of 45:1 resulted in total dominance by Synechococcus sp.; cultures grown under 5:1 and 15:1 supply ratios were dominated by Synedra radians, Nitzschia holsatica and Scenedesmus sp. NH₄⁺ and PO₄⁻³ uptake kinetics were not the same in cultures grown under different supply ratios, and ratios of saturated PO₄⁻³ to NH₄⁺ uptake rates were a good indicator of the N:P supply ratio under which the cultures were grown. This relationship was used to derive an index termed the Relative Field investigations were conducted on an oligotrophic coastal lake. NH₄⁺ and PO₄⁻³ uptake rates of size fractionated plankton (< and > 3 um), at a range of substrate concentrations, revealed that a large portion of the total uptake (50-90 % and 65-85 % for NH₄⁺ and PO₄⁻³, respectively) was attributable to cells in the < 3 um fraction. In addition, saturating PO₄⁻³, uptake rates of the > 3 um cells were less sensitive to incubation time than smaller cells. The ratio of saturated PO₄⁻³ to NH₄⁺ uptake rates were consistent with nutrient bioassay experiments, and indicated that N:P supply ratios in the lake were in the range where both N and P could be limiting to phytoplankton growth.Science, Faculty of
Botany, Department of
Graduate
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Pinkerton, Jeramy John. "Predicting the Potential Distribution of Two Threatened Stream Fish Species in Northeast Ohio." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1461189304.
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Oliveira, Sílvia Renata de. "Avaliação da qualidade da água e da carga de nutrientes do córrego do Cancã, município de São Carlos - SP." Universidade de São Paulo, 2003. http://www.teses.usp.br/teses/disponiveis/18/18138/tde-31102016-152545/.
Full textAbstract:
Os estudos em microbacias hidrográficas têm mostrado que as características físicas, químicas e biológicas das águas dos córregos e riachos possuem uma estreita relação com a composição do ambiente terrestre adjacente, refletindo as condições de uso e ocupação dos solos da bacia hidrográfica por eles drenada. A microbacia do Córrego do Cancã, localizada perpendicularmente ao Rio Monjolinho, situa-se em uma maior parte no município de São Carlos (SP), e foi estudada sob uma abordagem ecossistêmica. As coletas e análises de campo foram realizadas em sete transectos do córrego, em dois períodos hidrológicos distintos: seca e chuva. A caracterização física e química da água foi realizada através da análise do pH, da condutividade elétrica, da concentração de oxigênio, da temperatura, da concentração e da carga de nutrientes. Alguns dos parâmetros analisados foram comparados aos limites estabelecidos pela CONAMA segundo a resolução nº 20/1986. O córrego do Cancã, segundo a classificação proposta pela CONAMA, é um rio de classe-2. A água do córrego é levemente ácida tendendo à neutralidade em um gradiente da nascente à foz e caracteriza-se pela baixa condutividade elétrica. A temperatura variou entre os períodos avaliados e espacialmente foi influenciada pelos horários de coleta. As concentrações de nutrientes não foram elevadas, e das formas nitrogenadas as mais abundantes foram o nitrato (na estação mais impactada) e o amônio (após o represamento), com valores mais elevados no período de seca. A maior variabilidade foi observada para o nitrogênio total, sendo as maiores concentrações registradas na estação seca. Com base no índice de estado trófico, as águas do córrego do Cancã foram classificadas como mesotróficas. A forma da microbacia é irregular e ligeiramente alongada e pouco sujeita a enchentes. A área da microbacia foi determinada como sendo de 3,075 Km2. Na análise das comunidades planctônicas foram encontrados poucos representantes, distribuídos principalmente nas estações localizadas nos trechos inicial e médio do córrego, sendo, entretanto mais abundantes na nascente. Ocorreu predominância das clorofíceas e diatomáceas entre os organismos fitoplanctônicos e de rotíferos e cladóceros no zooplâncton. A microbacia está sujeita à práticas agrícolas e atividade pecuária semi-intensiva que alteram o balanço de massa dos principais nutrientes, contribuindo para o aumento da carga de nutrientes que são carreados do sistema terrestre para o aquático particularmente no período chuvoso.The studies peformed in small hydrographic basins have shown that the physical chemical and biological characteristics of the water in springs and streams have a close relation with the composition of adjacent terrestrial ecosystems, reflecting the uses and activities in the soils in the basin drained by them. The microbasin of Cancã stream belongs to the Monjolinho river basin and is mainly located inside the district of São Carlos (SP). In this study It has been evaluated under the ecosystemic approach. Field sampling and analysis were carried out in seven transects of the stream at two distinct hydrological periods: dry and rainy seasons. Physical and chemical analyses of water were performed by mesuring the pH, electrical conductivity, dissolved oxygen and the nutrient concentrations and loads. The parameters obtained were compared to the CONAMA limits, act nº 20/1986. The Cancã stream according to CONAMA proposed system, is classified as a class 2 water. The pH of Cancã water is slightly acid and there a tendency to the neutral from the source to the mouse. It is also characterized by low electrical conductivity. Water temperature has changed between dry and rainy periods and spatially it was influenced by the sampling timing. Nutrient concentrations are low and the main nitrogen compounds present were nitrate and ammonium, at the most impacted site, with highest values in the dry season. The highest variability was obtained for the total nitrogenvariability with higher concentrations at the dry season. Based on the trophic state index. The water of Cancã stream was classified as mesotrophic. The hydrographic microbasin has a non-regular shape, being slightly elongated and it has low vulnerability to floodings. The area of the catchment was found to be 3,071 Km2. Planktonic communities were composed by few organisms mainly occuring at the upper and middle stream streches, being most abundant at the first stretch. Clorophyceans and diatoms were the dominant groups among phytoplankton and the rotifers and cladocerans among the zooplankton. Cancã microbasin is subjected to a variety of agriculture and semi-intensive cattle enterprises that have changed major nutrient mass balances, contributing to the increase in nutrient loadings mainly via surface terrestrial runoff.
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Carden, Kerilynn M. "Macrophytes as fish habitat : the role of macrophyte morphology and bed complexity in fish species distributions /." Link to abstract, 2002. http://epapers.uwsp.edu/abstracts/2002/Carden.pdf.
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Barclay, Holly. "Propagation for the conservation and applied use of freshwater mussels." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610309.
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David, Gwendoline. "Spatio-temporal structuring of microbial communities in freshwater ecosystems." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASL049.
Full textAbstract:
Les microorganismes constituent la forme de vie la plus abondante et diverse sur Terre et ils présentent une grande diversité phylogénétique et métabolique. Ils sont donc impliqués dans les cycles biogéochimiques et les réseaux trophiques, ce qui en fait des acteurs clés du fonctionnement des écosystèmes. Pour décrypter l'écologie des microorganismes, il est essentiel de prendre en compte les échelles spatiales, temporelles et taxonomiques. Bien que des paramètres abiotiques et biotiques aient été identifiés comme influençant la composition des communautés microbiennes dans les écosystèmes aquatiques (e.g. la température, la prédation), des études complémentaires sont nécessaires pour mieux comprendre la structure des communautés microbiennes. Cependant, l'étude des interactions biotiques entre microorganismes est difficile en raison de leur petite taille, de la grande diversité et du peu d’individus cultivés. Cette thèse de doctorat vise à décrire la diversité microbienne au sein de deux types d'écosystèmes d'eau douce encore peu étudiés, et à identifier les facteurs qui déterminent la composition de leurs communautés microbiennes. La première partie de cette thèse vise à décrire la distribution spatiale (horizontale et verticale) des protistes planctoniques du lac Baïkal (Sibérie, Russie). Nous nous sommes intéressés à des échantillons collectés en été 2017 le long d'un transect de ~600 km couvrant les trois bassins du lac, de la surface aux profondeurs (~1500 m) et du littoral au pélagique. Les trois autres parties présentent une étude de huit ans de la composition et de la dynamique temporelle des communautés microbiennes des trois domaines du vivant, à la surface de cinq petits écosystèmes d'eau douce (sud-ouest de Paris, France). Les échantillons ont été collectés à deux fréquences, mensuelle (2011-2013) et saisonnière (2011-2019). Les communautés planctoniques ont été caractérisées par le séquençage des gènes ARNr 16S et 18S. Dans tous les écosystèmes, les communautés microbiennes sont très diverses, couvrant tous les super-groupes eucaryotes et procaryotes connus. Elles incluent des lignées typiquement marines (e.g. diplonémide, MAST), ce qui suggère que la frontière entre le marin et l'eau douce pourrait être plus fine que prévu. Des taxons encore peu connus ont aussi été détectés, tels que des bactéries du Candidate Phyla Radiation. Des analyses multivariées ont montré que seule une faible fraction de la variance des communautés peut être expliquée par les paramètres abiotiques étudiés. Pour les variations spatiales, nous avons constaté une faible variabilité des communautés du lac Baïkal dans les différents bassins, mais avec une forte stratification le long de la colonne d'eau. La profondeur, qui traduit les variations environnementales (e.g. la lumière) dans la colonne d'eau, semble influencer significativement les communautés. Les petits écosystèmes abritent différentes communautés microbiennes malgré leur proximité géographique. Pour les variations temporelles, deux dynamiques ont été identifiées. À l'échelle intra-annuelle, les communautés sont caractérisées par une forte saisonnalité. Cependant, moins de 2% des unités taxonomiques opérationnelles présentent une récurrence saisonnière. Cela suggère que les écosystèmes ont un fonctionnement saisonnier, malgré des dynamiques individuelles imprévisibles. À l'échelle interannuelle, les communautés microbiennes sont de plus en plus différentes au cours des huit années, indiquant des changements continus dans leur composition. Enfin, l’inférence des interactions microbiennes grâce aux réseaux de cooccurrence reflète les variations spatio-temporelles précédemment observées. En effet, les communautés sont plus complexes à la surface du lac Baïkal qu'en profondeur. De plus, les petits écosystèmes partagent des topologies similaires pour chaque saison. Cela souligne l'importance des interactions écologiques chez les communautés microbiennes, dans l'espace et le tempsMicroorganisms are the most abundant and diverse forms of life on Earth and are characterized by high phylogenetic and metabolic diversities. They are thus involved in biogeochemical cycles and trophic webs, which make them key players in ecosystem functioning. To decipher the ecology of microorganisms, it is crucial to include spatial, temporal and taxonomic scales. Although several abiotic and biotic parameters have been identified as drivers of microbial community composition in aquatic ecosystems (e.g. temperature, orthophosphate concentration, predation, symbiosis), more investigations are needed to better understand how microbial community structure is shaped. However, investigating biotic interactions involving microbes is challenging because of microbial features (e.g. small size, high diversity, low cultivation efficiency). This PhD thesis aims at describing the microbial diversity inside two overlooked types of freshwater ecosystems and at identifying the factors driving microbial community composition. The first section of this thesis aims at comprehensively describing the spatial distribution (horizontal and vertical) of planktonic microbial eukaryotes in Lake Baikal (Siberia, Russia). We focus on samples collected in summer 2017 along a transect of ~600 km across the three basins of the lake, from the surface to the deepest areas (~1500 m) and from littoral to open waters. The three other sections present an eight-year investigation of the composition and temporal dynamics of microbial communities belonging to the three domains of life at the surface of five small freshwater ecosystems (located in the South West of Paris, France). Samples were collected at two different frequencies, monthly (2011-2013) and seasonally (2011-2019). The composition of planktonic communities was assessed by the sequencing of the phylogenetic marker genes 16S and 18S rRNA. In all the ecosystems studied, the microbial communities were diverse, covering all eukaryotic and prokaryotic supergroups. Moreover, they included typically marine lineages, especially in Lake Baikal, (e.g. diplonemid, MAST) which suggested that the frontiers between marine and freshwater systems may be thinner than previously thought. They also included taxa that remain enigmatic, such as bacteria of the Candidate Phyla Radiation. Multivariate analysis showed that only a low fraction of the variance can be explained by the measured physico-chemical parameters. In terms of spatial variations, there was a weak variability of communities in Lake Baikal in summer across sampling basins, but a strong stratification along the water column. Depth, which is a proxy and a summary of the variations of the environmental conditions (e.g. light) along the water column, appeared to be a major driver of community composition. The small freshwater ecosystems harbored different microbial communities despite their geographic proximity. In terms of temporal variations, two types of patterns were detected. At the intra-annual scale, global communities were characterized by a strong seasonality. However, at the Operational Taxonomic Unit level, less than 2% of the community were characterized by recurrent seasonal patterns. This suggests that ecosystems have a yearly seasonal functioning, despite the presence of some unpredictable microbial dynamics. At the inter-annual scale, microbial communities experienced an increase of dissimilarities over the eight years, indicating turnovers in community composition. Finally, the structure of the communities studied through co-occurrence network inference reflected the spatio-temporal variations previously observed. Indeed, communities were more connected at the surface of Lake Baikal compared to the bottom. Moreover, ecosystems shared similar structural properties at each season. This underlines the importance of ecological interactions in the composition of microbial community over space and time
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McKinnon-Newton, Laurie. "Ecology of plankton in a terminal lake Walker Lake, Nevada, USA /." abstract and full text PDF (free order & download UNR users only), 2007. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1446303.
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Yakushin, Alexander. "Ecology and morphology of selected diatom species in the genus Aulacoseira." Thesis, University of Ulster, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326314.
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Hunsinger, Glendon Brian. "Organic matter exchanges between freshwater-tidal wetlands and the Hudson River." Diss., Online access via UMI:, 2009.
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Pandeirada, Mariana Sofia Oliveira. "Studies on freshwater woloszynskioids (Dinophyceae)." Master's thesis, Universidade de Aveiro, 2013. http://hdl.handle.net/10773/11811.
Full textAbstract:
Mestrado em Biologia Aplicada - Ecologia, Biodiversidade e Gestão de EcossistemasOs dinoflagelados são um grupo de protistas com características intra- e extracelulares invulgares, encontrados tanto em habitats marinhos como de água doce. Estes organismos são tradicionalmente classificados como tecados ou atecados tendo em conta a constituição da sua região externa, conhecida como anfiesma. Esta região compreende uma camada única de vesículas achatadas subjacentes ao plasmalema, as quais podem ser preenchidas com placas celulósicas mais ou menos espessas nos dinoflagelados tecados, ou com placas celulósicas muito finas, ou mesmo não possuírem placas, nos dinoflagelados atecados. Durante o século XX, contudo, foi demonstrado que algumas espécies atecadas do género Gymnodinium tinham um anfiesma constituído por numerosas placas celulósicas finas. Tais espécies foram transferidas para um novo género, Woloszynskia, o qual foi posteriormente objeto de controvérsia, principalmente associada com o estabelecimento da espécie tipo e a possibilidade de compreender outros grupos taxonómicos, sendo portanto polifilético. Recentemente, uma série de estudos confirmaram a última ideia, e vários géneros foram criados para receber espécies de Woloszynskia, conhecidas como woloszynskióides. Esses géneros foram distribuídos por diferentes famílias: Tovellia, Jadwigia, Esoptrodinium e Opisthoaulax na nova família Tovelliaceae; Borghiella e Baldinia na nova família Borghiellaceae; Biecheleria e Biecheleriopsis incluídos na família Suessiaceae. Estas mudanças taxonómicas foram suportadas por dados moleculares e diferenças morfológicas na estrutura do estigma, organização do apex da célula e tipo de quisto de resistência. O conhecimento taxonómico sobre a diversidade e distribuição de dinoflagelados de água doce em Portugal Continental foi reunido pela primeira vez numa "checklist" e aqui apresentado (Capítulo 2). As entradas na lista foram definidas tendo em conta pesquisa filogenética recente, em particular mudanças taxonómicas que afetam os limites a nível genérico dos taxa. Registos publicados de espécies de dinoflagelados de água doce, retirados de 37 referências, formam a base do inventário, aos quais foi adicionada documentação para 12 taxa ainda não referenciados para Portugal (11 espécies e uma forma). Duas novas espécies de woloszynskióides para a ciência, não incluídas nesta "checklist", são aqui apresentadas (Capítulos 3, 4). A morfologia das células e quistos é descrita, bem como a ultraestrutura das células móveis e aspetos particulares do ciclo de vida. Filogenias baseadas em sequências de LSU rDNA confirmam as novas espécies. A primeira espécie pertence à família Tovelliaceae, género Tovellia (Capítulo 3). O epíteto específico escolhido foi aveirensis, o qual constitui uma referência ao nome da universidade, bem como da cidade onde foi encontrada: Campus da Universidade de Aveiro, Aveiro, Portugal. Tovellia aveirensis possui a característica peculiar de produzir um quisto de resistência com paracíngulo e ornamentado com numerosos processos ramificados, que não só difere do quisto bipolar e quase não ornamentado do género, mas também de todos os outros descritos para woloszynskióides. Morfologicamente esta difere de outras espécies de Tovellia principalmente por ter uma linha de pontos posicionada ao nível do limite posterior do cíngulo, rodeando a célula, e por não possuir uma placa antapical distinta, à volta da qual as séries de placas do hipocone poderiam estar dispostas. A segunda espécie de woloszynskióide foi encontrada na área alagada do Ribeiro da Palha, Nariz, Aveiro, Portugal, e num lago de água doce na Escócia (Capítulo 4). Esta pertence à família Borghiellaceae, género Borghiella, e foi nomeada B. andersenii em honra do Prof. Robert A. Andersen, que primeiro estabeleceu cultura da mesma a partir de material colhido na Escócia. Morfologicamente é idêntica à B. dodgei, divergindo desta principalmente por ter um epicone arredondado e um par de vesículas anfiesmais alongadas (PEV) mais curto, com menos pontos e delineado por duas a três placas apicais. B. andersenii é capaz de se reproduzir assexuadamente tanto no estado móvel, por fissão, como no estado imóvel, com produção de quistos de divisão, algo que nunca foi referenciado para Borghiellaceae. Além disso, evidências mais fortes de reprodução sexuada para esta família foram ainda observadas em culturas de B. andersenii, nomeadamente planozigotos e aparentes quistos de resistência. Dois outros woloszynskióides, designados MSP1 e MSP12, são aqui brevemente descritos (Capítulo 5). Estes foram colhidos respetivamente num lago da Gafanha da Boavista, próxima da Vista Alegre, Ílhavo, Aveiro, e no mesmo local, em Portugal, onde B. andersenii foi encontrada. Tanto os resultados morfológicos como filogenéticos sugerem que são duas novas espécies de Tovellia, evolucionariamente próximas de T. aveirensis.
Dinoflagellates are a group of protists with intra- and extracellular unusual features, found in both marine and freshwater habitats. These organisms are traditionally classified as armoured or thecate, and unarmoured or athecate taking into account the constitution of their outer region, known as amphiesma. This region comprises a single layer of flat vesicles underlying the plasmalemma, which can be filled with more or less thick cellulosic plates in the thecate dinoflagellates, or with very thin cellulosic plates or no plates at all in the athecate ones. During the 20th century, however, it was demonstrated that some athecate species of the genus Gymnodinium had an amphiesma constituted by numerous thin cellulosic plates. Such species were transferred to a new genus, Woloszynskia, which has been later object of controversy, mainly associated with the establishment of the type species and the possibility to comprise other taxonomic groups, thus being polyphyletic. Recently, a series of studies have confirmed the latter idea, and several genera have been created to receive Woloszynskia species, known as woloszynskioids. Those genera have been distributed over different families: Tovellia, Jadwigia, Esoptrodinium and Opisthoaulax in the new family Tovelliaceae; Borghiella and Baldinia in the new family Borghiellaceae; Biecheleria and Biecheleriopsis ranged with the family Suessiaceae. These taxonomic changes have been supported by molecular data and by morphological differences in eyespot structure, organization of the cell apex and type of resting cyst. Taxonomic knowledge about the diversity and geographic distribution of freshwater dinoflagellates in continental Portugal were assembled in a checklist for the first time and here presented (Chapter 2). Entries in the list were defined taking into account recent phylogenetic research, particularly the resulting taxonomic changes that affect genus-level limits of taxa. Published reports of freshwater dinoflagellate species, taken from 37 references, form the basis of the inventory, to which it was added documentation for 12 previously unreported taxa (11 species and one form). Two new woloszynskioid species for science, not included in this checklist, are presented here (Chapter 3, 4). The morphology of cells and cysts is described as well as the ultrastructure of motile cells and particular aspects of the life cycle. LSU rDNA-based phylogenies confirm the new species. The first one belongs to the family Tovelliaceae, genus Tovellia (Chapter 3). The species epithet chosen was aveirensis, which constitutes a reference to the name of the university as well as the city where it has been found: University of Aveiro Campus, Aveiro, Portugal. Tovellia aveirensis has the peculiar feature of producing a resting cyst with paracingulum and ornamented by numerous branched processes, which not only differs from the bipolar and almost not ornamented Tovellia cyst, but also from all others described for woloszynskioids. Morphologically, it differs from other species of the genus mainly by having a line of knobs placed at the posterior edge of the cingulum, surrounding the cell, and lacking a distinct antapical plate around which the series of plates on the hypocone could be arranged. The second new woloszynskioid has been found in a flooded area in Ribeiro da Palha stream, Nariz, Aveiro, Portugal, and in a freshwater pond in Scotland (Chapter 4). It belongs to the family Borghiellaceae, genus Borghiella, and was named B. andersenii in honor of Prof. Robert A. Andersen, who first established a culture of this species from material collected in Scotland. Morphologically, it is identical to B. dodgei, diverging from this mainly by having a rounded epicone and a shorter pair of elongate amphiesmal vesicles (PEV) with fewer knobs and lined on each side by two to three apical plates. B. andersenii is able to reproduce asexually both in the motile stage, by fission, and non-motile stage, with production of division cysts, something that has never been reported within Borghiellaceae so far. Furthermore, stronger evidences of sexual reproduction for this family have yet been observed in B. andersenii cultures, namely planozygotes and apparent resting cysts. Two other woloszynskioids, designated as MSP1 and MSP12, are here briefly described (Chapter 5). These have been collected respectively in a farm pond at Gafanha da Boavista, near Vista Alegre, Ílhavo, Aveiro, and in the same place where B. andersenni was found. Both morphologic and phylogenetic results suggest that they are two new Tovellia species, evolutionarily close to T. aveirensis.
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Avlijas, Suncica. "Factors affecting the distribution and abundance of an invasive freshwater mysid." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=114218.
Full textAbstract:
The freshwater shrimp Hemimysis anomala is a recent Ponto-Caspian invader of the Great Lakes – St. Lawrence River basin. Based on its invasion history, high predation rate and the naiveté of the ecosystems in which it has been introduced, it has the potential to exert strong impacts on native food webs. Risk assessment and effective monitoring of the spread of this invader require information about the environmental factors that limit its local abundance and distribution. A literature review suggests that H. anomala has broad environmental tolerances but may be limited by low water conductivity levels, high local flow, and low dissolved oxygen. An empirical model derived from results of a field study in the St. Lawrence River identified specific conductivity and shoreline heterogeneity as important predictors of H. anomala occurrence and abundance across sites. The relationship between conductivity and H. anomala occurrence is further supported by experimental evidence that demonstrates lower functional responses at lower conductivity levels. Distance from shore and depth were also good predictors of H. anomala abundance, which was maximal in areas close to shore and at depths above 2 m.La crevette d'eau douce Hemimysis anomala est une espèce envahissante provenant de la région Ponto-Caspienne qui a été découverte récemment dans le bassin des Grands Lacs et du fleuve Saint-Laurent. En raison de ses fortes tendances envahissantes, de son taux de prédation élevé et de la naïveté des écosystèmes dans lesquels elle a été introduite, elle pourrait avoir des impacts considérables sur les réseaux alimentaires locaux. Afin d'évaluer les risques et de surveiller de manière efficace la dispersion de cette espèce, point est besoin d'avoir accès à de l'information sur les facteurs environnementaux qui limitent son abondance locale et sa distribution. Une recension de la littérature suggère que H. anomala fait preuve de tolérance environnementale, mais qu'une basse conductivité d'eau, de hauts courants locaux et une basse concentration d'oxygène dissous peuvent diminuer cette tolérance. Un modèle empirique, mis au point à partir des résultats d'une étude de terrain menée dans le fleuve Saint-Laurent, démontre que la conductivité spécifique et l'hétérogénéité du rivage constituent des facteurs de prédiction de la présence et de l'abondance de H. anomala à travers les sites. La relation entre la conductivité de l'eau et la présence de H. anomala est, en outre, soutenue par des preuves expérimentales qui mettent en exergue une réponse fonctionnelle réduite à de bas niveaux de conductivité. La distance du rivage et la profondeur sont aussi de bons indices d'abondance de H. anomala; la concentration de crevettes atteint d'ailleurs son point le plus haut près du rivage et à plus de deux mètres de profondeur.