I investigated effects of environmental change on disease, and effects of disease on ecosystems, using a freshwater zooplankton host and its fungal parasite. This research involved lake surveys, manipulative experiments, and mathematical models. My results indicate that ecosystem characteristics such as habitat structure, nutrient availability, and quality of a host’s resources (here, phytoplankton) can affect the spread of disease. For example, a survey of epidemics in lakes revealed direct and indirect links between habitat structure and epidemic size, where indirect connections were mediated by non-host species. Then, in a mesocosm experiment in a lake, manipulations of habitat structure and nutrient availability interactively affected the spread of disease, and nutrient enrichment increased densities of infected hosts. In a separate laboratory experiment, poor quality resources were shown to decrease parasite transmission rate by altering host foraging behavior. My experimental results also suggest that disease can affect ecosystems through effects on host densities and host traits. In the mesocosm experiment, the parasite indirectly increased abundance of algal resources by decreasing densities of the zooplankton host. Disease in the experimental zooplankton populations also impacted nutrient stoichiometry of algae, which could entail a parasite-mediated shift in food quality for grazers such as the host. Additionally, I showed that infection dramatically reduces host feeding rate, and used a dynamic epidemiological model to illustrate how this parasite-mediated trait change could affect densities of resources and hosts, as well as the spread of disease. I discuss the implications of these ecosystem–disease interactions in light of ongoing changes to habitat and nutrient regimes in freshwater ecosystems.

The limnological knowledge of waters in arid regions, especially Mongolia, is still insufficient. It was the goal of the Mongolian-German research project “Limnological Particularities of Characteristic Waterbodies in the Uvs Nuur Basin” to develop a systematic inventory of waters, describe their morphological, hydrophysical, chemical and biological characteristics and to generalize the framework of abiotic and biotic factors that determine their character. During the field work, carried out from 1996 to 1999, samples of water, sediments, benthic and planktonic biota were taken from 76 places at 15 stagnant water bodies, 21 streams and several groundwater bodies; morphological, hydrological, physical and hydrochemical measurements were made. Chemical and biological analyses were carried out in Germany. The most important taxonomical groups were determined by German and international specialists. The results of the work are presented and discussed separately for running waters, lakes and groundwater. Based on these findings, several general topics are dealt with: factors shaping the character of water bodies, food webs, biogeography, spatial sequence of water bodies, typology and protection issues. A checklist of 596 taxa was compiled; 109 additional taxa from the Russian and Mongolian literature were included. Two species (Cyclops glacialis Flößner 2001 and Acanthocorbis mongolica Paul 2011) were new for the science and 103 species were new reports for Mongolia. A regional stream typology with 11 different types was developed using the criteria ecoregion, altitude and catchment area. The typology developed for stagnant waters comprises 9 types based on altitude, lake area, existence of an outflow and relative depth. This dissertation comprises 139 pages and an appendix of 59 pages, 50 tables, 94 figures and a map.

The limnological knowledge of waters in arid regions, especially Mongolia, is still insufficient. It was the goal of the Mongolian-German research project “Limnological Particularities of Characteristic Waterbodies in the Uvs Nuur Basin” to develop a systematic inventory of waters, describe their morphological, hydrophysical, chemical and biological characteristics and to generalize the framework of abiotic and biotic factors that determine their character. During the field work, carried out from 1996 to 1999, samples of water, sediments, benthic and planktonic biota were taken from 76 places at 15 stagnant water bodies, 21 streams and several groundwater bodies; morphological, hydrological, physical and hydrochemical measurements were made. Chemical and biological analyses were carried out in Germany. The most important taxonomical groups were determined by German and international specialists. The results of the work are presented and discussed separately for running waters, lakes and groundwater. Based on these findings, several general topics are dealt with: factors shaping the character of water bodies, food webs, biogeography, spatial sequence of water bodies, typology and protection issues. A checklist of 596 taxa was compiled; 109 additional taxa from the Russian and Mongolian literature were included. Two species (Cyclops glacialis Flößner 2001 and Acanthocorbis mongolica Paul 2011) were new for the science and 103 species were new reports for Mongolia. A regional stream typology with 11 different types was developed using the criteria ecoregion, altitude and catchment area. The typology developed for stagnant waters comprises 9 types based on altitude, lake area, existence of an outflow and relative depth. This dissertation comprises 139 pages and an appendix of 59 pages, 50 tables, 94 figures and a map.:Acknowledgments ii Abstract iii List of Tables iii List of Figures vi 1 Introduction 1 1.1 Significance of the investigations 1 1.2 Aims of the investigations 2 1.3 Sequence of field research activities 3 1.4 Area of investigation 4 1.4.1 Topographic situation and morphology .4 1.4.2 Climate 5 1.4.3 Geology and soils 9 1.4.4 Vegetation 10 1.4.5 Population and economy 10 1.4.6 Former limnological investigations in the Uvs Nuur Basin 11 1.4.7 Short description of the investigated waters 12 2 Methods 15 2.1 Sampling 15 2.2 Field measurements 16 2.3 Laboratory analyses and data evaluation 19 3 Results and discussion 26 3.1 Rivers 26 3.1.1 Morphology and hydrology 26 3.1.2 Runoff dynamics 34 3.1.3 Water temperature and freezing 38 3.1.4 Chemical properties 39 3.1.5 Aquatic biota 43 3.2 Lakes 53 3.2.1 Formation and morphometry 53 3.2.2 Water level changes and water balance 58 3.2.3 Temperature and overturn dynamics of the water body 63 3.2.4 Vertical gradients of physico-chemical parameters and chlorophyll 65 3.2.5 Horizontal gradients in Uvs Nuur: surface temperature and suspended matter 69 3.2.6 Salinity and ionic composition 71 3.2.7 Nutrients and trophic state 74 3.2.8 Sediments 79 3.2.9 Aquatic biota 83 3.3 Groundwater 95 3.3.1 Hydrology 95 3.3.2 Chemical composition 96 3.3.3 Biota 98 4 Conclusions and synthesis 99 4.1 Exogenous factors influencing the character of water bodies 99 4.1.1 Biological structure of running waters 100 4.1.2 Biological structure of lakes 104 4.2 Food webs 105 4.3 Biogeographical classification 110 4.4 Spatial sequence of water bodies and material flows 113 4.5 Transformation of the water bodies 116 4.6 Typology of water bodies 117 4.7 Protection of landscape and waters 121 5 Literature 124 6 Appendices 140 6.1 Tables 140 6.2 Cross sections and longitudinal profiles of rivers 169 6.3 Microscopical images of algal species 175 6.4 Satellite images 179 6.5 Photographs of sampled waters 182

Chorine is used by the Village Creek Waste Water Treatment Plant to kill pathogenic microorganisms prior to discharge of the effluent into the Trinity River. The residual chlorine in the river impacted aquatic life prompting the U.S. Environmental Protection Agency in December 1990 to require dechlorination using sulfur dioxide. One pre-dechlorination and four post-dechlorination assessments of phytoplankton, periphyton, and zooplankton communities were conducted by the Institute of Applied Sciences at the University of North Texas. Dechlorination had no effect on the phytoplankton community. The periphyton community exhibited a shift in species abundance with a more even distribution of organisms among taxa. No change occurred in zooplankton species abundance, however, there was a decrease in zooplankton density following dechlorination.

I miljöövervakningen av haven runt Sverige har manuell mikroskopi av plankton länge varit den huvudsakliga tekniken för att övervaka växtplanktonbestånden och algblomningar. Nya tekniker utvärderas, men det är inte känt hur resultaten från de nyare teknikerna relaterar till varandra. Två tekniker som utvärderas av SMHI, flödesmikroskopi och DNA-streckkodning, har inte tidigare jämförts i litteraturen. Båda teknikerna har dock jämförts med traditionell mikroskopi. I det här projektet har provserier för DNA-streckkodning och automatiserad mikroskopi med Imaging FlowCytobot (IFCB) samlats in parallellt under en expedition i Egentliga Östersjön, Öresund, Kattegatt och Skagerrak. En bildklassificerare konstruerades med ett konvolutionellt neuronnät, som användes för att klassificera bilderna som tagits med IFCB:n. Resultaten från IFCB:n jämfördes med dem från DNA-streckkodning av 18S rRNA-genen. Jämförelsen visade stark korrelation mellan klassificeringen av bilder och DNA-streckkodning för vissa kiselalger (R>0.8), men teknikernas resultat skilde sig också åt i många fall. Skillnaderna kan studeras för att hitta svagheter i de båda teknikerna och utveckla dem vidare. / In environmental monitoring of the seas around Sweden, manual counting with microscopy is used to monitor the plankton communities and algal blooms. New techniques are currently being evaluated, including imaging flow cytometry and DNA metabarcoding, but it is not known how results from the different techniques relate to one another. Previous work has not compared imaging flow cytometry with metabarcoding, although both methods have been compared to traditional microscopy. In this project, samples for DNA metabarcoding and imaging flow cytometry with the Imaging FlowCytobot (IFCB) have been collected in parallel in the Baltic Proper, Öresund, Kattegat, and Skagerrak. To be able to process the large number of images from cytometry, an image classification algorithm based on convolutional neural networks and transfer learning was developed, which was used to classify the images collected. The results were compared to those obtained with 18S rRNA metabarcoding of the protist community. This new approach of comparing imaging flow cytometry with metabarcoding resulted in a strong (R>0.8) correlation for some diatom taxa, but discrepancies between the technologies were also observed. The discrepancies can be further studied to identify weaknesses in both techniques and refine them further.

The purpose of this investigation is to compare the dissolved and suspended organic material in Lake Dallas to that coming into the lake through Pecan Creek.

published_or_final_version / Ecology and Biodiversity / Master / Master of Philosophy

O aumento do consumo de agrotóxicos, em geral nos países em desenvolvimento cuja base econômica é a agricultura, como no Brasil (primeiro no ranking mundial), tem sido relacionado à expansão da degradação dos ecossistemas e à perda da biodiversidade, principalmente das espécies não alvo, incluindo ainda os riscos inerentes à saúde humana. Além disso, a ausência de políticas e programas mais efetivos relacionados à regulação e uso de agrotóxicos no Brasil, bem como o estabelecimento de normas restritivas baseadas em resultados gerados em países de clima temperado, tornam-se cada vez mais preocupantes, pois podem subestimar os reais riscos da contaminação ambiental por agrotóxicos em ecossistemas tropicais. Nesse contexto, o presente estudo teve como objetivo avaliar os efeitos diretos e indiretos do agrotóxico pyrimethanil, um fungicida utilizado em diversas culturas de climas temperado e tropical, sobre a comunidade aquática tropical, considerando experimentos laboratoriais e o uso de modelos ecossistêmicos para avaliação destes efeitos. Para atender aos objetivos propostos foram realizados testes de toxicidade com as espécies Pseudokirchneriella subcapitata (alga), Ceriodaphnia silvestrii e Daphnia similis (zooplâncton) e Danio rerio (peixes), além de um experimento em mesocosmos, monitorado em longo prazo (durante 15 dias antes e 366 dias após a contaminação), avaliando as variações físicas e químicas, bem como as respostas das comunidades zooplanctônicas e fitoplanctônicas frente à contaminação por pyrimethanil, em uma concentração média de 1,36 mg.L-1. Nos testes de toxicidade, as CEs obtidas foram de 0,67 mg.L-1 (crônica) e 3,26 mg.L-1 (aguda) para C. silvestrii; de 3,65 mg.L-1 (agudo) para D. similis; de 9,65 mg.L-1 para P. subcapitata e para D. rerio os valores obtidos para imobilidade foram de 10,45 mg.L-1 (96h) e 13,77 mg.L-1(48h) e para a mortalidade foram de 27,45 mg.L-1 (96h) e 32,17 mg.L-1 (48h). Pelos resultados dos experimentos em mesocosmos verificaram-se efeitos negativos diretos sobre o zooplâncton (redução da densidade e alteração na composição de espécies) e indiretos sobre o fitoplâncton, decorrentes da diminuição da pressão de pastagem, além do desaparecimento de algumas espécies mais sensíveis. Os efeitos tóxicos observados foram além do período em que foi observada a degradação completa do pyrimethanil, demonstrando o alto impacto do agrotóxico em ecossistemas aquáticos e a complexidade da dinâmica desse tipo de contaminação em ecossistemas naturais. O design experimental revelou-se adequado, gerando informações importantes sobre os impactos dos agrotóxicos nos ecossistemas aquáticos. A partir dos resultados obtidos sugere-se que a utilização de espécies nativas de regiões tropicais seja ampliada nos testes de toxicidade laboratoriais, sendo fundamental que os mesmos sejam complementados com os experimentos em modelos ecossistêmicos, o que permite uma avaliação dos efeitos diretos e indiretos dos contaminantes em nível de população e comunidade, bem como uma melhor compreensão destes efeitos nas funções e serviços ecossistêmicos. / The increase in the consumption of pesticides, mainly in developing countries whose economic base is agriculture, as Brazil (first in the world ranking), has been associated to the expansion of ecosystem degradation and biodiversity losses, especially of non-target species, also including the risks to human health. In addition, the absence of policies and effective programs related to the regulation and use of pesticides in Brazil, and the establishment of restrictive standards based on results generated in temperate countries, make it becomes increasingly worrisome because it may underestimate the real risks of environmental contamination by pesticides in tropical ecosystems. In this context, the present study aim to evaluate the direct and indirect effects of the pesticide pyrimethanil, a fungicide used in many temperate and tropical crops, upon a tropical aquatic community, considering laboratory experiments and the use of ecosystem models to evaluate these effects. To achieve the proposed objectives toxicity tests were performed with the species Pseudokirchneriella subcapitata (algae), Ceriodaphnia silvestrii and Daphnia similis (zooplankton) and Danio rerio (fish), as well as an experiment in mesocosms, monitored for a long-term (15 days before and 366 days after infection), evaluating the physical and chemical variations, and also the responses of phytoplankton and zooplankton communities across the pyrimethanil contamination in an average concentration of 1.36 mg.L-1. In toxicity tests, the ECs obtained were 0.67 mg.L-1 (chronic) and 3.26 mg L-1 (acute) for C. silvestrii; 3,65 mg.L-1 (acute) for D. similis; 9.65 mg.L-1 for P. subcapitata; and the values obtained for D. rerio immobility were 10.45 mg.L-1 (96h) and 13.77 mg.L-1 (48h) and mortality were 27.45 mg.L-1 (96h) and 32.17 mg.L-1 (48h). The results of the experiments in mesocosms showed direct negative effects on zooplankton (reduced density and change in species composition) and indirect effects on phytoplankton, resulted from the decrease in grazing pressure in addition to the exclusion of some sensitive species. Even after the complete degradation of pyrimethanil, toxic effects were observed, demonstrating the high impact of this pesticide on aquatic ecosystems and the complexity of the dynamics of this type of contamination in natural ecosystems. The design of the experiment revealed to be appropriate for the study, generating important information about the impacts of pesticides on aquatic ecosystems. From the results, it is suggested an increase in the use of native tropical species in the toxicity laboratory tests. Also, this process should be complemented with experiments in ecosystem models, allowing the evaluation of the direct and indirect effects of contaminants in the population and in community level as well as a better understanding of these effects on ecosystem functions and services.

O filo Ctenophora tem sido negligenciado em estudos faunísticos e ecológicos no Brasil. São escassos os registros de espécies e pouco se sabe sobre a distribuição e abundância destes animais em águas brasileiras. Muito dessa falta de informações sobre o grupo se deve às dificuldades em se coletar e preservar espécimes. O presente estudo consistiu em um esforço no sentido de se conhecer um pouco mais sobre os ctenóforos, nos âmbitos faunístico, taxonômico e ecológico. A tese foi dividida em seis capítulos: o primeiro faz uma introdução ao estudo dos Ctenophora; o segundo traz descrições das sete espécies que ocorrem no Canal de São Sebastião; o terceiro traz uma chave de identificação para as treze espécies registradas para a costa brasileira, incluindo um glossário de termos específicos; o quarto aborda o problema taxonômico relativo ao ctenóforo Mnemiopsis leidyi, apresentando uma solução para tal; o quinto contempla a biologia populacional de M. leidyi na costa brasileira, a questão do impacto predatório da espécie em diversas regiões do mundo e sua recente introdução nos mares do Norte e Báltico; o último apresenta considerações gerais sobre os resultados dos capítulos anteriores. Desta forma, procurei abordar diversos aspectos da taxonomia e biologia dos ctenóforos presentes na costa brasileira e espero, assim, ter conseguido efetuar algum avanço no conhecimento deste grupo, ainda muito carente de estudos no Brasil e no mundo. / The phylum Ctenophora is pour studied in Brazil. Species records for the Brazilian coast are scarce in the literature. The distribution patterns and abundance of ctenophores in the region are almost unknown. The scarcity of data aims mostly to the difficulties in collecting and preserving specimens. This study consisted in an effort to increase knowledge on the faunistics, taxonomy and ecology of the ctenophores from Brazilian waters. Dissertation was divided in six chapters. The first on introduces the Ctenophora study. The second presents description of the seven species found in the São Sebastião Channel. The third chapter is an identification key to the species reported for the Brazilian coast, with a glossary on specific terms. The fourth regards the taxonomical problem of Mnemiopsis leidyi and suggests a solution for it. The fifth presents the population biology of M. leidyi from the Brazilian coast, the predatory impact of the species in several areas of the world and its recent introduction in the North and Baltic seas. The last chapter summarizes the final conclusions of the previous chapters. Thus, in hope of fulfilling a gap on these animals knowledge, I tried to contemplate several aspects of taxonomy and biology of the ctenophore species from the Brazilian coast.

Espécies de medusozoários com ciclos de vida muito diferentes habitam distintos mares e oceanos ao redor do mundo. Em uma escala regional, algumas espécies de hidrozoários estão amplamente distribuídas no Atlântico Sul-ocidental, (litorais do Brasil e Argentina), com populações habitando ambientes heterogêneos e estruturados. A relação entre a distribuição das espécies e a maior parte dos fatores ambientais é pouco conhecida. Deste modo, o objetivo de nosso estudo é pesquisar os padrões de distribuição e a estrutura genética populacional de duas espécies de hidrozoários do Atlântico Sul-ocidental em relação a: (1) as diferentes histórias naturais e (2) as distintas estruturas de massas d\'água do ambiente marinho. As espécies estudadas foram Olindias sambaquiensis (meroplanctônica, ciclo de vida: ovo ⊲ plânula ⊲ pólipo ⊲ medusa ⊲ ovo) e Liriope tetraphylla (holoplanctônica, ciclo de vida: ovo ⊲ plânula ⊲ medusa ⊲ ovo). Dados sobre a ecologia e história natural de tais espécies foram coletados e análises filogeográficas foram conduzidas utilizando os marcadores mitocondriais 16S e CO1. Nossos resultados revelaram um padrão filogeográfico similar para ambas as espécies. As populações brasileiras são basais e têm uma maior diversidade nucleotídica que as populações argentinas, as quais ocupam uma posição apical. O Rio da Prata não é uma barreira efetiva e introgressão possivelmente ocorre em ambas as espécies, podendo estar relacionada à circulação das massas d\'água. A estrutura genética encontrada para Olindias sambaquiensis pode estar relacionada com seu hábito demersal e afinidade com massas d\'água costeiras, e para Liriope tetraphylla com seu ciclo reprodutivo e auto-recrutamento. / Medusozoan species, with quite different life-cycles, inhabit different seas and oceans around the world. In a regional scale, some hydrozoan species are widespread along the Southwestern Atlantic Ocean (Brazilian and Argentinean shores), with populations distributed along a heterogeneous and structured environment. The relation between the distribution of the species and most of the biological and environmental factors is still largely unknown. Therefore, the aim of this study is to investigate the distributional patterns and genetic structure of populations of two hydrozoan species of SW Atlantic Ocean in relation to: (1) the different life histories and (2) the water masses structures of the marine environment. The species studied were the meroplanktonic Olindias sambaquiensis (life cycle: egg ⊲ planula ⊲ polyp ⊲ medusa ⊲ egg) and the holoplanktonic Liriope tetraphylla (life cycle: egg ⊲ planula ⊲ medusa ⊲ egg). We gathered data on the ecology and natural history of the species, and carried out phylogeographic analyses using CO1 and 16S DNA markers. Our results have shown similar phylogeographical patterns and genetic structures for both species. The Brazilian populations are basal and have a higher nucleotidic diversity than the apical Argentinean populations. The Rio de La Plata river is not an effective barrier, and introgression possibly occurs for both species and might be related to the circulation of the water masses. Biologically, the genetic structure found for Olindias sambaquiensis must be related to its demersal habit and close affinity to coastal water masses, and that found for Liriope tetraphylla must be related to its reproductive cycle and auto-recruitment.