A two year study was initiated in 1973 to examine effects of substantial (3.8 fold; from a 1962-66 mean of 39 million to about 150 million in 1973 and 1974) increases in sockeye (Oncorhynchus nerka) Walbaum) fry numbers on zooplankton abundance in Babine Lake. Several lake areas and stationsware sampled for zooplankton bimonthly from May to October during 1973 and 1974 and compared to data gathered between 1958 and 1962 prior to a large scale enhancement program for sockeye stocks. Zooplankton biomass had decreased up to 70% in some areas of the lake during 1973, but only 40% in 1974. Decreases in numbers were also evident. Although seasonal changes in fry diet followed changes in zooplankton species abundance, feeding was selective. The less abundant but larger forms, Daphnia and Heterocope together comprised 70% of the diet during summer, while Cyclops and Diaptomus formed the bulk (87%) of the diet in late fall. Significant decreases in Daphnia and Diaptomus abundance and increases in nauplii-early copepodite abundance had occurred by 1973. The increased 1974 zooplankton abundance relative to 1973 was attributed to decreased mid-summer fry numbers in the lake. Field data suggested low Diaptomus numbers contributed to much higher fry mortality (about double in 1974) compared to 1973. An experimental study of species selectivity by sockeye fry indicated that they selected Cyclops and Diaptomus adults. The larger copepods, Heterocope and Epischura, were rejected by fry encountering zooplankton for the first time. Copepodites and nauplii were rejected, but less so when preferred prey were scarce. Prey activity, in my experiments, could not be used to predict predation vulnerability and hence the species selectivity displayed by the fry. Light and temperature had little effect on Cyclops, Dlaptomus and Heterocope activity. / Science, Faculty of / Zoology, Department of / Graduate

Reservatórios artificiais são ecossistemas de grande importância econômica e social, porém, alteram as características hidrológicas e ecológicas do meio, interferindo na organização das comunidades bióticas que desempenham papel fundamental na transferência de energia no ecossistema. Nesses ambientes, pode existir uma organização espacial e temporal, tornando diferenciada a composição e distribuição das comunidades. Com o objetivo de verificar essa organização, a comunidade zooplanctônica, com ênfase nas populações de Cladocera, foi avaliada em amostras coletadas nas estações distribuídas no eixo longitudinal dos reservatórios do médio e baixo Tietê (SP), nos meses de fevereiro, maio, julho e outubro de 2000. Os dados obtidos foram relacionados às características ambientais, tais como pH, condutividade, temperatura, oxigênio dissolvido, material em suspensão, nutrientes e clorofila a desse ambiente. Os resultados apontaram para uma diferenciação esperada ao longo do eixo longitudinal do rio Tietê, tanto nas características físicas e químicas, quanto na abundância e distribuição dos organismos. Os reservatórios do médio Tietê estiveram mais eutrofizados do que os reservatórios do baixo Tietê nos períodos analisados, provavelmente devido à carga de poluentes advinda da região mais urbanizada e industrializada do Estado de São Paulo, a qual enriquece o sistema. Grande parte desse material é assimilado ou sedimentado nos primeiros reservatórios, ocasionando a melhora significativa da qualidade da água no eixo longitudinal da cascata, para a maioria das variáveis. Acompanhando as características físicas e químicas, a comunidade biológica também apresenta diferenciação no eixo longitudinal do sistema em cascata com maior abundância de organismos no médio Tietê, onde a comunidade de Cladocera esteve composta principalmente por espécies de pequeno tamanho, principalmente do gênero Ceriodaphnia, enquanto que esses valores diminuíram significativamente no baixo Tietê, onde espécies de maior tamanho dos gêneros Daphnia e Simocephalus foram relativamente mais abundantes. A diversidade de espécies foi maior nas regiões de maior abundância de organismos. As características ambientais encontradas no sistema levaram ao aparecimento de organismos com vários graus de alterações morfológicas; em alguns casos as malformações podem ser congênitas e em outros foi evidente o ataque por microrganismos / Artificial reservoirs are ecosystems with broad economic and social importance; however, they modify hydrological and ecological characteristics of the environment, interfering on the organization of biotic communities, which, in turn, play fundamental role in the transference of energy in the ecosystem. Spatial and temporal organization may occur on these environments, resulting in distinct communities composition and distribution. Aiming to verify this organization, the zooplanktonic community had been evaluated, focusing on Cladocera populations. The analysis was based on samples collected on stations distributed along the longitudinal axis of the medium and low Tietê river reservoirs (SP), in february, may, july, and october, 2000. Data obtained had been correlated to environmental parameters, such as pH, conductivity, temperature, dissolved oxygen, suspended material, nutrients, and chlorophyll-a. The results indicated an expected differentiation on physical and chemical characteristics along the longitudinal axis of Tietê river, as much as on the organisms\' abundance and distribution. The reservoirs from medium Tietê were found to be more eutrophicated than those from low Tietê, in the periods analyzed, a result probably related to the pollutant discharge coming from the more urbanized and industrialized region of São Paulo state, which enriches the system. Most of this material form sediment or becomes assimilated on the first reservoirs, resulting in significant improvement of the water quality on the cascade longitudinal axis, for the majority of the variables analyzed. Similarly to physical and chemical characteristics, the biological community also showed differentiation in the longitudinal axis of the cascade system. Higher abundance of organisms occurred on the medium Tietê, where the Cladocera community had been composed mostly by small sized species, mainly of the genus Ceriodaphnia, while significant reduction of these values was observed on low Tietê, where higher size species of the genus Daphnia and Simocephalus were relatively more abundant. The species diversity was higher on the regions with elevate abundance of organisms. The environmental characteristics found in the system caused the emergence of organisms with several degrees of morphological alterations; in some cases, the malformations can be congenital and, in others, the attack by microorganisms was evident

Este projeto de pesquisa foi desenvolvido nos reservatórios e tributários do Médio e Baixo rio Tietê, São Paulo, com o objetivo de avaliar a composição, distribuição e densidade das espécies de Copepoda Calanoida e Cyclopoida e sua relação com a disposição dos reservatórios construídos em série (cascata), os quais apresentam diferenças na morfometria, período e área de inundação, grau de trofia (relacionando aos usos e ocupação da bacia hidrográfica), vazão e tempo de residência da água. Para tanto, foram realizadas coletas nos reservatórios e tributários nos meses de fevereiro, maio, julho e outubro/2000, quantificando as principais variáveis físicas, químicas e biológicas, além da análise qualitativa e quantitativa do zooplâncton, com ênfase em Copepoda Calanoida e Cyclopoida. Os resultados demonstram que apesar de ser verificada a melhoria da qualidade da água nos reservatórios a jusante, ainda ocorrem contribuições pontuais via tributários e difusas pelas atividades desenvolvidas na bacia hidrográfica, aumentando a concentração das formas nitrogenadas e fosfatadas, influenciando diretamente nas condições tróficas dos reservatórios e, conseqüentemente, na composição, densidade e distribuição das populações planctônicas. Os reservatórios classificam-se como eutróficos ou mesotróficos (dependendo da sua localização no rio Tietê e da sazonalidade) e os rios como eutróficos, principalmente em decorrência das elevadas concentrações de fósforo e clorofila.Em relação à comunidade zooplanctônica, os Copepoda e Rotifera foram mais abundantes, com uma variação espacial e sazonal relacionada às condições tróficas e temperatura, bem como aos mecanismos diferenciados do controle operacional das barragens (vazão e tempo de residência da água). As espécies de Copepoda encontradas no sistema foram Notodiaptomus iheringi, Notodiaptomus evaldus, Notodiaptomus deitersi, Argyrodiaptomus azevedoi Thermocyclops decipiens, ) Thermocyclops minutus, Thermocyclops inversus, Mesocyclops longisetus, Mesocyclops brasilianus, Mesocyclops meridianus, Mesocyclops ogunus, Acanthocyclops ogunus e Paracyclops chiltoni, sendo N. iheringi, N. evaldus, T. decipiens e T. minutus as espécies dominantes, com diferenças na distribuição e abundância em função dos locais de amostragem (tributários ou reservatórios) e período de coleta (sazonalidade). / This research project was developed in Tietê River reservoirs and tributaries, São Paulo, Brazil, aiming to evaluate the composition, distribution and density of Copepoda Calanoida and Cyclopoida species and its relationship with reservoirs disposition in Tietê River, built in series (cascade), which present differences in morphometry, flood period and area, trophic level (related to the hydrographic basin uses and occupation), discharge and water residence time. For that, collections were accomplished in reservoirs and tributaries on February, May, July and October/2000, quantifying the main physical, chemical and biological variables, besides qualitative and quantitative zooplankton analysis, with emphasis in Copepoda Calanoida and Cyclopoida. Results demonstrate that, in spite of the improvement of water quality verified downstream reservoirs, it still happen punctual tributary contributions, diffused due to activities developed in the hydrographic basin, increasing nitrogenous and phosphate forms concentration, influencing directly the reservoir trophic conditions and, consequently, composition of species, density and distribution. Reservoirs are classified as eutrophic or mesotrophic (depending on its location in Tietê River and sazonality) and the rivers as eutrophic, due mainly to the high phosphorus and chlorophyll concentrations. In relation to the zooplankton community, Copepoda and Rotifera were the most abundant, with spacial and seasonal variationrelated to trophic conditions and temperature, as well as to the barrier differentiated operational control mechanisms (discharge and water residence time). The Copepoda species found in the system were Notodiaptomus iheringi, Notodiaptomus evaldus, Notodiaptomus deitersi, Argyrodiaptomus azevedoi, Thermocyclops decipiens, Thermocyclops minutus, Thermocyclops inversus, Mesocyclops longisetus, Mesocyclops brasilianus, Mesocyclops meridianus, Mesocyclops ogunus, Acanthocyclops ogunus and Paracyclops chiltoni; being N. iheringi, N. evaldus, T. decipiens and T. minutus the dominant species, with differences in the distribution and abundance in function of the sampling places (tributaries or reservoirs) and collection period (sazonality).

A represa do Lobo (Broa) é um ecossistema bastante estudado, entretanto, nos últimos anos foram observadas várias alterações nas suas condições, devido, principalmente, ao processo de eutrofização. Para o maior entendimento dos processos que ocorrem nos sistemas aquáticos, a análise integrada do ecossistema em termos de bacia hidrográfica é de suma importância. Além disso, as comunidades biológicas, com destaque o zooplâncton, representam as respostas estruturais e funcionais do sistema. Dessa forma, o objetivo do trabalho foi analisar a distribuição da comunidade zooplanctônica frente à heterogeneidade ambiental, de sistemas lóticos e lêntico e dos impactos na área de entorno da bacia hidrográfica do Lobo. Para tanto, foram realizadas coletas em quatro períodos (chuvoso, seco e intermediários) em 17 pontos de coleta distribuídos no reservatório e nos tributários. Foram avaliadas as variáveis físicas e químicas da água (temperatura, pH, oxigênio dissolvido, condutividade, transparência da água, nutrientes, material em suspensão e metais), variáveis climatológicas (temperatura do ar, precipitação e velocidade do vento) e variável biológica (clorofila a). Para a comunidade zooplanctônica foi determinada a composição, densidade e abundância, bem como índices biológicos. De acordo com os resultados, a represa do Lobo apresentou, de uma forma geral, homogeneidade espacial nas variáveis analisadas, apresentando condições eutróficas em todos os pontos. A comunidade zooplanctônica, representada por 64 espécies, também indicou a degradação da represa, como por exemplo, o aumento da representatividade do gênero Brachionus, o desaparecimento de Bosmina coregoni e o aparecimento de Moina micrura. Por sua vez, os tributários apresentaram heterogeneidade ambiental em muitas variáveis, com o ponto AB/L2, com condições características de ambientes mais poluídos, e o ponto JG, com altas concentrações de clorofila a. A comunidade zooplanctônica foi representada por 93 espécies, com a maior constância de espécies que possuem lórica (Kellicottia bostoniensis, Keratella tropica, Platyas quadricornis, Lecane bulla e Lecane lunaris) e da família Chydoridae. A heterogeneidade temporal foi mais marcada que a espacial, com o agrupamento dos meses de maior precipitação (janeiro e outubro) com maiores graus de trofia e maiores concentrações de formas fosfatadas. / The Lobo reservoir (Broa) is a well-studied ecosystem, however, in recent years have passed through several changes in its conditions, mainly, due to the process of eutrophication. For better understanding the processes occurring in aquatic systems, the integrated analysis of the ecosystem in terms of watershed is of utmost importance. In addition, the biological communities, especially zooplankton, represent the structural and functional responses of the system. Thus, the objective was to analyze the distribution of zooplankton front of environmental heterogeneity in lotic and lentic systems and impacts in the area surrounding the basin of the Lobo. For this purpose, samples were collected in four periods (rainy, dry and intermediates) in 17 sampling stations distributed in the reservoir and tributaries. We evaluated the physical and chemical variables of water (temperature, pH, dissolved oxygen, conductivity, water transparency, nutrients, suspended solids and metals), climatic variables (air temperature, precipitation and wind speed) and the biological variable (chlorophyll a). For the zooplankton community was determined the composition, density and abundance, and biological indices. According to the results, the Lobo reservoir showed, in general, spatial homogeneity in the variables analyzed, with eutrophic conditions at all points. The zooplankton community, represented by 64 species, also indicated the degradation of the dam, such as, the increased representation of the genus Brachionus, the disappearance of Bosmina coregoni and the appearance of Moina micrura. On the other hand, the tributaries are heterogeneous in many environmental variables, with the station AB/L2 with conditions characteristic of more polluted environments, and JG station, with high concentrations of chlorophyll a. The zooplankton community was represented by 93 species, with the greater constancy of loricate species (Kellicottia bostoniensis, Keratella tropica, Platyas quadricornis, Lecane bulla and Lecane lunaris) and the family Chydoridae. The temporal heterogeneity was more marked than the spacial heterogeneity, with the grouping of the months of highest rainfall (January and October) with greater degrees of trophy and higher concentrations of phosphorylated forms.

This thesis resulted from an examination of Lake Worth plankton in comparison to plankton found in similar bodies of water throughout the United States.

This thesis deals with ecotoxicity tests of selected substances used in agriculture and horticulture. It is focused on the determination of acute and chronic toxicity of selected herbicides. These herbicides are sold commercially, specifically Finalsan (active substance is nonanoic acid), the product of Neudorff GmbH KG company, and Dominator (active substance is glyphosate, isopropylamine salt) by Dow AgroSciences Ltd. Next tested substances are potassium nitrate and sodium nitrate - common agricultural fertilizers. Potassium dichromate was also tested. Potassium dichromate is very toxic for aquatic environment and it is used as the standard in acute tests. Tests were carried out in terms of effects on aquatic systems, due to very good solubility in water of selected substances. The tests were performed on the organism Daphnia magna.

Re-creation and building new small freshwater habitats belong among the important management activities within the Protected Landscape Area Kokořínsko - Máchův kraj (Czech Republic) for almost two decades. These pools keep the water within the landscape and serve as the habitats for vulnerable species of amphibians and invertebrates, which I have studied within this thesis. Most studies focusing on studying metacommunities of small water bodies have been based on the data from one or two seasons, and thus completely neglect the development of composition of these metacommunities over longer periods of time. This thesis builds on previous research on the species composition of small ponds in the Kokořínsko Protected Landscape Area, which had been done in 2005 and 2006. In 2009 and 2017, sampling in the same ponds continued. I investigated the influence of spatial and environmental variables of individual ponds on the species composition of ostracods, copepods and molluscs in specific years and how has the representation of individual species changed among those years. With one exception, I have not observed any new incoming species of copepods and ostracods since 2006; the number of species had in fact decreased. In the case of molluscs, there was a significant exchange of species between individual...

One of the defining characteristics of our current epoch—the Anthropocene—is modification of nutrient cycles. At regional to global scales, humans have fundamentally reshaped the availability of carbon, nitrogen, and phosphorus. These changes are particularly apparent in freshwater ecosystems, which receive surface and groundwater inputs of nutrients from agriculture, fossil fuel use, and wastewater. In this thesis, I investigated how the addition of nutrients affects microbial community and biogeochemistry in two extreme environments: the hypereutrophic shallow Utah Lake and nutrient-limited Arctic permafrost streams. In my first chapter, I used bioassay and dilution bioassay experiments to identify what factors control harmful algal blooms in Utah Lake. Specifically, I measured phytoplankton and cyanobacteria growth, cyanotoxin production, and aquatic N-fixation potential. I included physical factors, such as temperature, light, nutrient concentrations, and pH, as well as biological factors, such as top-down control by zooplankton grazers. Phytoplankton showed a threshold behavior at 0.005 mg/L for soluble reactive phosphorus and 0.14 mg/L for dissolved inorganic nitrogen. Surprisingly, nitrogen fixation rates were only high in active bloom samples and were augmented by the addition of both nitrogen and phosphorus. Also contrary to our hypothesis, zooplankton preferentially grazed cyanobacteria over total phytoplankton. In my second chapter, I investigated how permafrost degradation might influence dissolved organic matter (DOM) in Arctic stream networks. Specifically, I used nutrient and labile carbon additions to simulate the effects of permafrost thaw DOM degradation and microbial community in three distinct permafrost-covered catchments on the North Slope of Alaska. The alpine catchment had higher biodegradability but lower DOM concentration across seasons compared with the lake-influenced and tundra catchments. For all catchments, there were strong seasonal changes in microbial community and distinct responses to nutrient addition. The addition of nutrients stimulated DOM biodegradation in the late season—the period of the year when permafrost DOM release typically occurs. Microbial communities differed by catchment type, but overall diversity was similar. Together, these experiments highlight the diverse downstream consequences of human alteration of global carbon, nitrogen, and phosphorus cycles. Even in extreme systems, alteration of the microbial community regulating many of these cycles has potential to exacerbate ecosystem and climate change, so understanding our influence over biogeochemical cycles and microbial interactions is vital for informing future management practices and planetary boundaries.

Lake Baikal (Siberia, Russia) is the oldest, the deepest and the most voluminous lake on Earth. During the last century, Baikal has experienced gradual increases in temperature but remains highly oligotrophic with increases in primary productivity limited to the warmest parts of the lake. Using whole body RNA:DNA ratio as an indicator of metabolic rate, we demonstrate that the key primary consumer in Baikal's plankton, Epischura baikalensis (Copepoda: Calanoida), is a capital breeder that relies on lipid storage to maintain productivity. In individuals from nature, the RNA:DNA ratio correlated with lipid content in samples from cold, low phytoplankton density locations from Baikal's North and Central basins, but not in samples from warmer South basin and Maloe More strait. Lipid reserves, both visually assessed and measured by Nile Red fluorescence, correlated positively with phytoplankton density. In laboratory experiments the RNA:DNA ratio responded to starvation and temperature in non-reproducing, low lipid storage females, but not in individuals with developed ovaries or high lipid storage. This indicates that, unlike many other zooplankton crustaceans, E. baikalensis uses resource storage to support current reproduction, which buffers the dependency of metabolic rate on current feeding conditions. We discuss possible effects of such buffering on E. baikalensis competition with non-endemic, largely income-feeding zooplankton species whose frequency is currently increasing in Baikal pelagia.

Les plans d’eau, du «bas delta» du fleuve Sénégal sont de plus en plus confrontés aux problèmes d’efflorescences à cyanobactéries qui menacent la ressource en eau des États riverains. Une étude, couplant approches in situ et expérimentales, a été menée pour analyser les principaux facteurs biologiques qui interviennent dans l’apparition et le contrôle de ces phénomènes. L’étude in situ a permis d’analyser la distribution spatio-temporelle du phyto et du zooplancton et les relations entre ces communautés dans 13 sites représentatifs à différentes saisons. L’importance croissante, des cyanobactéries et notamment d’espèces à potentiel toxique comme Cylindrospermopsis raciborskii, Anabaena solitaria, Anabaena flos-aquae et Microcystis aeruginosa a été mise en évidence. Certains aspects des communautés zooplanctoniques (avantage des cyclopoïdes sur les calanoïdes, présence-abondance d’espèces indicatrices, faibles biomasses par rapport au phytoplancton) indiquent une tendance à l’eutrophisation des plans d’eau. Une forte association entre communautés phyto et zooplanctoniques a été mise en évidence par des analyses multivariables. Une étude expérimentale sur le broutage a montré que les cyanobactéries filamenteuses sont consommées et/ou fractionnées avec une efficacité variable selon les brouteurs et que le zooplancton est un facteur important de contrôle descendant des cyanobactéries filamenteuses (jusqu’à 50% du stock par jour). Des expériences de toxicité ont clairement mis en évidence des effets négatifs des cyanobactéries sur la survie et la croissance du zooplancton, mais avec une sensibilité différente des espèces aux toxines. Des dégradations musculaires et intestinales ainsi que des modifications de l’activité de l’acétylcholinestérase ont été mises en évidence chez des copépodes mais plusieurs éléments suggèrent que les effets ne seraient pas liés aux cyanotoxines classiques, mais plutôt liés à la présence d’autres métabolites émis soit par les cyanobactéries, soit par la flore associée puisque les cultures utilisées n’étaient pas axéniques. / The lower delta of the Senegal river faced with problems linked to cyanobacterial bloom which threaten the water resource of The riverine countries. A study, coupling in situ and experimental approaches, was carried out to analyze the biologicalfactors which intervene in the appearance and the control of these phenomena. The in situ study made analyzed the space time distribution of the phyto- and the zooplankton communities and their relationships in 13 representative sites at various seasons. The increasing importance, of the cyanobacteria and in particular of species with toxic potential like Cylindrospermopsis raciborskii, Anabaena solitaria, Anabaena flos-aquae and Microcystis aeruginosa was highlighted.Certain aspects of the zooplanktonic communities (importance of cyclopoïds compared to calanoïds, presence-abundance ofindicating species, low zooplankton biomasse compared to the phytoplankton) indicate a trend towards eutrophication. Astrong association between phyto- and zooplankton communities was highlighted by multivariable analyzes. Grazing experiments showed that the filamentous cyanobacteria are consumed and/or split with a variable efficiency according to the grazers and that the zooplankton exert a strong top-down control of the filamentous cyanobacteria (up to 50% of stock perday). Toxicity experiments clearly highlighted negative effects of the cyanobacteries on zooplankton survival and growth, butwith a variable sensitivity according to the species. Ultrastructural deformations and muscular and intestinal degradations aswell as modifications of the acétylcholinestérase activity were highlighted for copepods, but several elements suggest thatthe effects would not be related to the traditional cyanotoxins, but rather related to the presence of other metabolites emittedeither by the cyanobacteria, or by the associated flora since the cultures used were not axenic.