This dissertation characterizes the influences of water chemistry on the acute toxicity of lead (Pb) to two of the long-standing sentinel test organisms commonly employed by the United States Environmental Protection Agency (USEPA), the fathead minnow (Pimephales promelas) and daphnid (Ceriodaphnia dubia), for parameterization of an acute Pb Biotic Ligand Model (BLM). In addition, a toxicogenomic approach was employed to identify genes that might serve as molecular markers of Pb exposure and long-term effects, as well as provide new insights as to the underlying toxic mechanisms of chronic Pb exposure in P. promelas. The endpoints of growth, reproduction, Pb accumulation, prey capture ability, and swimming performance of P. promelas were examined to assess the influences of water chemistry during chronic Pb exposures and to potentially link microarray-identified genes to outcomes of ecological significance. Importantly, this work revealed that calcium does not protect against acute toxicity to C. dubia or chronic Pb accumulation by P. promelas, indicating that current hardness-based regulations are inappropriate and provide further support for the need for alternative approaches to setting environmental regulations for Pb. The findings reported herein should facilitate the arrival of such an approach in the form of a new acute Pb BLM. However, different responses with respect to the influences of water chemistry on the acute toxicity of Pb were exhibited by these species suggesting that development of separate BLMs for P. promelas and C. dubia should be considered to ensure adequate protection for both species. Furthermore, the influences of water chemistry were found to be inconsistent during acute and chronic Pb exposures to P. promelas and thus caution against inferring chronic effects from acute exposures. A number of Pb-responsive genes were identified that exhibited a strong potential for serving as robust indicators of Pb exposure and accumulation in P. promelas. While these genes also provided insight as to the likely toxic mechanisms of Pb, additional work will be necessary to firmly link these genes to chronic outcomes of ecological relevance in the context of ambient water chemistry.

Planktivorous fish affect the species composition, size and morphology of their zooplankton prey by size selective predation. Remains of cladocerans are deposited in the lake sediments and this microfossil community hence reflects the historical changes in the planktivore fish community. Most earlier work on quantitatively inferring past planktivory deals with ephippia (resting eggs) of Daphnia, however these remains are very scarce in northern Swedish lakes. In these lakes, often dominated by fish that are not obligate planktivores, such as perch (Perca fluviatilis), the individual size to a large degree determines the type of resource consumed. Therefore, in these lakes, the size distribution as well as the density of the fish community determines the overall planktivoryThis thesis deals with evaluating the use of Bosmina remains in the sediment as indicators of past planktivory. I developed a transfer function based on Bosmina remains to be used in oligotrophic lakes with omnivorous species to reconstruct past planktivory. I test the transfer function in a lake where the history is to a large extent known. Furthermore, in this thesis a novel quantitative measure of planktivore pressure, the PCC (Planktivore Community Capacity) was developed. It was also possible to compare the morphology measurements of carapace length and mucro length of contemporary Bosmina sampled in the lake, with the same measurements on microfossils of Bosmina sedimented during the corresponding time period. By using the resurrection approach this thesis also evaluates the use of Ceriodaphnia clones as indicators of micro-evolutionary responses to past planktivory.From the studies in this thesis I can draw some major conclusions; the morphological measurements carapace length and mucro length of Bosmina can be used to infer past planktivory in northern Swedish lakes. PCC has a higher explanatory power than CPUE in these lakes dominated by omnivorous fish. The morphology of the contemporary Bosmina corresponds well with the remains found in the sediment dating from the same time period. Both the contemporary and microfossil Bosmina changes in body size characteristics was in turn strongly related to PPC. Finally, the hatching of Ceriodaphnia ephippia is promising for studying past planktivory, both because of the high viability of the ephippia and the relationship between eye area and inferred PCC.

Pacific salmon (Oncorhynchus spp.) production strongly influences the ecosystems, cultures and economies of the Northeast Pacific. Historical variability in population sizes is complex, reflecting natural and human drivers. The nature and extent of such ‘exogenous’ controls on salmon and their nursery ecosystems are poorly understood, a significant impediment to sustainable fisheries management. Novel applications of paleolimnology demonstrate that past sockeye salmon abundances and nursery system ecology can be reconstructed from lake sediments. This thesis focuses on employing these techniques to establish the forcing mechanisms underlying salmon population and ecosystem dynamics, and determine the effects and interactions of fisheries management. I provided the first reconstruction for a southern North American stock, which demonstrated the influences of both conspicuous (e.g. commercial fishery, main-stem damming) and uncertain human impacts (e.g. local damming) on endangered salmon declines. By reconstructing ecological variability at multiple trophic levels, I established that rehabilitative management (e.g. fish stocking) may have permanently altered nursery lake rearing capacity, a change potentially reinforced by recent atmospheric changes. This work highlights significant impediments to ongoing recovery efforts. I extended my analysis of salmon management by exploring the interactive impacts of exotic salmon stocking on a remote northern lake. I demonstrated the utility of long-term data in pre-emptively understanding the complex impacts of stocking by documenting the long-term trajectories in limnological conditions. Integrating modeling, limnological and paleolimnological analyses, I determined that climate change and salmon introductions compound to alter chemical, physical and biological lake variables, ultimately altering ecosystem structure and functioning. Finally I reconstructed salmon abundances over the past six millennia, the longest record and the first Canadian example to date, demonstrating salmon production is cyclical and far more variable than observed in the monitoring record. My analyses established that North Pacific salmon production is forced by ocean-atmospheric teleconnections ultimately linked to climatic variability in the tropical Pacific. Further analyses provided the first evidence for a possible solar forcing of Holocene salmon production on both orbital and higher frequency time scales. Cumulatively this research improves our understanding of the processes underlying variability in Pacific salmon and their natal ecosystems, important to ecologically-informed future management. / Thesis (Ph.D, Biology) -- Queen's University, 2008-09-27 02:41:54.576

Submitted by Livia Mello (liviacmello@yahoo.com.br) on 2016-10-10T20:21:26Z No. of bitstreams: 1 DissGML.pdf: 3541713 bytes, checksum: 0c6f05408f457af46db02eef2c8ca598 (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-10-20T19:53:18Z (GMT) No. of bitstreams: 1 DissGML.pdf: 3541713 bytes, checksum: 0c6f05408f457af46db02eef2c8ca598 (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-10-20T19:53:24Z (GMT) No. of bitstreams: 1 DissGML.pdf: 3541713 bytes, checksum: 0c6f05408f457af46db02eef2c8ca598 (MD5) / Made available in DSpace on 2016-10-20T19:53:32Z (GMT). No. of bitstreams: 1 DissGML.pdf: 3541713 bytes, checksum: 0c6f05408f457af46db02eef2c8ca598 (MD5) Previous issue date: 2016-06-10 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / In recent years, increased use of titanium dioxide nanoparticles (TiO 2 NPs) in consumer products and technological devices has raised concerns regarding their environmental impacts and their risks to human health. Ecotoxicological studies have been used as a tool to analyze the toxic potential of TiO 2 NP S in different trophic levels, such as primary producers (algae) and first order consumers (cladocerans). In the present study, the chronic effects of TiO2 NPS on the population growth of the microalgae chlorophycean Pseudokirchneriella subcapitata was evaluated during an exposure period of 96 hours, under conditions of temperature and photoperiod similar to those found in tropical ecosystems. New methods were developed for the separation of the aggregates between the algae cells and TiO2 NPS, whose formation was observed at above 0.01 mg L-1 concentrations after a period of 96 hours’ exposure. The only effective method was the one in which the cells were washed three times with a metal chelator (EDTA), with duration of 1 minute for each wash. In the toxicity chronic test, there was obtained a significant inhibition of algal growth from the concentration of 64 mg L-1 of TiO2 NPs, with a concentration of 50% inhibition of algal cells (96 h - IC50) of 201.22 mg L -1 in 96 h of exposure. Then, it was evaluated the acute effects of exposure by contact and the chronic effects of TiO2 NPs for the cladoceran Ceriodaphnia silvestrii, using contaminated food (Pseudokirchneriella subcapitata) as a route of exposure. In acute toxicity tests was obtained the average value of EC50 - 48 h of 77.57 mg L-1. In chronic toxicity tests, it was observed significant differences in survival from the concentration of 0.01 mg L-1, while for the body length, the number of eggs and neonates produced, toxic effects were observed from the concentration of 1 mg L-1. These results indicate that the nano-TiO2 NPS had a deleterious effect on the growth of Pseudokirchneriella subcapitata only at concentrations above those normally found in natural aquatic environments. For the cladoceran Ceriodaphnia silvestrii, the route of dietary exposure indicated a greater toxic effect. / Nos últimos anos, o aumento do uso das nanopartículas de dióxido de titânio (nano-TiO2) em produtos de consumo e em dispositivos tecnológicos tem gerado preocupações relativas aos seus impactos ambientais e seus riscos à saúde humana. Estudos ecotoxicológicos têm sido utilizados como uma ferramenta para analisar o potencial tóxico das nano-TiO2 em diversos níveis tróficos, tais como produtores primários (algas) e consumidores de primeira ordem (cladóceros). No presente estudo, os efeitos crônicos das nano-TiO2 sobre o crescimento populacional da microalga clorofícea Pseudokirchneriella subcapitata foi avaliado durante um período de exposição de 96 horas, sob condições de temperatura e de fotoperíodo semelhantes às encontradas em ecossistemas de regiões tropicais. Foram desenvolvidas novas metodologias para separação dos agregados entre as células algais e as nano-TiO2, cuja formação foi observada nas concentrações acima de 0,01 mg L -1 após um período de exposição de 96 horas. O único método eficiente foi aquele em que as células foram lavadas três vezes com um quelante de metal (EDTA), com duração de 1 minuto para cada lavagem. No teste de toxicidade crônico obteve-se inibição significativa do crescimento algal a partir da concentração de 64 mg L-1 de nano-TiO2, com uma concentração de inibição a 50% das células algais (CI 50 - 96h) de 201,22 mg L-1 em 96 h de exposição. Em seguida, foram avaliados os efeitos agudos via exposição por contato e os efeitos crônicos das nano-TiO2 para o cladócero Ceriodaphnia silvestrii, utilizando o alimento (Pseudokirchneriella subcapitata) contaminado como via de exposição. Nos testes de toxicidade aguda foi obtido o valor médio de CE50 - 48 h de 77,57 mg L-1. Nos ensaios de toxicidade crônica, diferenças significativas foram observadas na sobrevivência a partir da concentração de 0,01 mg L -1, enquanto que para o comprimento corporal, o número de ovos e o número de neonatas produzidos, os efeitos tóxicos foram observados a partir da concentração de 1 mg L-1. Tais resultados indicam que as nano-TiO2 possuíram um efeito deletério sobre o crescimento de Pseudokirchneriella subcapitata somente em concentrações acima daquelas normalmente encontradas em ambientes aquáticos naturais. Para o cladócero Ceriodaphnia silvestrii, a via de exposição alimentar indicou um maior efeito tóxico. / CNPq: 305698/2013-30 / FAPESP: 2014/14139-3 e 2016/00753-7

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