Mercury (Hg) is an important environmental contaminant due to its global distribution, tendency to bioaccumulate, and toxicity to wildlife. However, Hg has received little attention in amphibians compared to other vertebrates, despite the fact that amphibian population declines have been documented worldwide and environmental contaminants are believed to contribute to some declines. During my dissertation research, I used a pluralistic approach which combined field studies and manipulative laboratory and mesocosm experiments to examine the bioaccumulation and ecological effects of environmentally relevant Hg exposure routes acting at various early life stages in amphibians. By collecting amphibians in the field at the Hg-contaminated South River, VA, I confirmed that amphibians exhibiting different life histories and occupying different ecological niches (Plethodon cinereus, Eurycea bislineata, and Bufo americanus) can bioaccumulate sufficient levels of Hg to warrant concern (Chapter 2) and female Bufo americanus transfer accumulated Hg to their eggs (Chapter 3). Maternal transfer of contaminants is a parental effect which typically has negative consequences for offspring because early development is a critical organizational period in the ontogeny of vertebrates. Through laboratory observations and mesocosm experiments, I examined the short and long-term effects of maternal contaminant exposure on offspring, and found the negative effects of maternal Hg exposure manifested either immediately at the embryonic stage or later during the larval stage, depending on the year in which the study was conducted (Chapters 4 and 5). Lastly, using a factorial laboratory experiment, I examined whether the latent effects of maternal transfer of contaminants manifests differently depending on the environment in which offspring develop, and found both maternal and dietary Hg exposure independently produced negative, but different, sublethal effects on larval development. Most importantly, maternal exposure to Hg combined with high dietary Hg exposure later in ontogeny had a lethal effect in larvae (Chapter 6). This study is one of the first to demonstrate that the latent effects of maternally transferred contaminants may be exacerbated by further exposure later in ontogeny, findings that may have important implications for both wildlife and human health. / Ph. D.

A variabilidade espacial e temporal do suprimento larval pode influenciar fortemente as taxas de recrutamento em populações de invertebrados marinhos do entre marés, e, assim, determinar os padrões de abundância e distribuição de adultos. No entanto, o comportamento de larvas antes do assentamento, e a sua condição fisiológica, podem também desempenhar um papel importante. Há vários fatores que influenciam a qualidade fisiológica de uma larva, sendo um deles o efeito materno, ou seja, a forma como os recursos são manipulados pelas mães para produzir sua prole, especialmente como afeta a fecundidade. Outro fator importante é o estado trófico do ambiente onde estágios iniciais se desenvolvem em estágios finais pré-competentes. No entanto, pouco se sabe sobre a relação entre esses dois processos e se a variabilidade natural das condições da costa realmente provoca uma pior qualidade no desempenho juvenil e nas taxas de recrutamento. Neste estudo nós analisamos se os processos que afetam a qualidade embrionária e larval são independentes ou interativas, e também se as condições ambientais ao longo de uma costa subtropical pode mediar tendências de qualidade de larvas à mesoescala e também determinar padrões de distribuição de invertebrados sésseis do entre marés. Usamos a craca Chthamalus bisinuatus como modelo biológico, e experimentos de laboratório e de campo foram realizados para explorar a relação de diversas variáveis ambientais nos padrões de distribuição destes cirripédios. Testamos também se as oscilações naturais na disponibilidade de alimento determinam padrões espaciais e temporais da qualidade da larva produzida e os efeitos da disponibilidade de alimento para as mães e para os seus descendentes na qualidade do estágio larval final deste organismo. Os resultados obtidos nessa tese apontam para a importância da disponibilidade de alimento na coluna d\'água em determinar padrões de abundância e tamanho dos organismos adultos, bem como a relação com o grau de exposição à ação de ondas na manutenção de populações adultas. Concluímos também que mudanças sazonais na produtividade primária tem um efeito na fecundidade e qualidade da larva produzida ao longo do ano por esses cirripédios. Finalmente pudemos demonstrar que pequenas alterações na quantidade de alimento fornecida à mães e larvas de Chthamalus são suficiente para provocar plasticidade de alguns tratos larvais importantes para os processos e sucesso do recrutamento destes organismos. / Spatial and temporal variability of larval supply can strongly influence the recruitment rates in populations of marine intertidal invertebrates, and thus determine the abundance and distribution patterns of adults. However, the behavior of larvae prior to settlement, and its physiological condition, may also play an important role. There are several factors that influence the physiological quality of a larva, one of them being maternal effects, that is, the way resources are allocated by mothers to produce their offspring, especially the way it affects fecundity. Another important factor is the trophic state of the environment where early stages develop into competent pre-final stages. However, little is known about the relationship between these two processes and if the natural variability of coastal conditions actually causes poorer quality in young performance and recruitment rates. In this study we analyzed the processes affecting embryonic and larval quality and if they are independent or interactive, and also if the environmental conditions along a subtropical coast can mediate trends in quality larvae to mesoscale and also determine sessile intertidal invertebrates distribution patterns. We used the barnacle Chthamalus bisinuatus as a biological model, and laboratory and field experiments were conducted to explore the relationship of various environmental variables in the patterns of distribution of these barnacles. We tested also if natural fluctuations in food availability determine spatial and temporal patterns of larvae quality produced and the effects of food availability for mothers and their descendants in the quality of the final larval stage of this organisms. The results obtained in this thesis point to the importance of the food availability in the water column in determining patterns of abundance and size of adult organisms, and the relationship with the degree of exposure to wave action in the maintenance of adult populations. We also conclude that seasonal changes in primary productivity has an effect on fecundity and quality of the larvae produced throughout the year by those barnacles. Finally we were able to demonstrate that small changes in the amount of food provided to mothers and larvae Chthamalus are enough to cause plasticity of some important larval traits which impacts the processes and success of recruitment in these organisms.

A variabilidade espacial e temporal do suprimento larval pode influenciar fortemente as taxas de recrutamento em populações de invertebrados marinhos do entre marés, e, assim, determinar os padrões de abundância e distribuição de adultos. No entanto, o comportamento de larvas antes do assentamento, e a sua condição fisiológica, podem também desempenhar um papel importante. Há vários fatores que influenciam a qualidade fisiológica de uma larva, sendo um deles o efeito materno, ou seja, a forma como os recursos são manipulados pelas mães para produzir sua prole, especialmente como afeta a fecundidade. Outro fator importante é o estado trófico do ambiente onde estágios iniciais se desenvolvem em estágios finais pré-competentes. No entanto, pouco se sabe sobre a relação entre esses dois processos e se a variabilidade natural das condições da costa realmente provoca uma pior qualidade no desempenho juvenil e nas taxas de recrutamento. Neste estudo nós analisamos se os processos que afetam a qualidade embrionária e larval são independentes ou interativas, e também se as condições ambientais ao longo de uma costa subtropical pode mediar tendências de qualidade de larvas à mesoescala e também determinar padrões de distribuição de invertebrados sésseis do entre marés. Usamos a craca Chthamalus bisinuatus como modelo biológico, e experimentos de laboratório e de campo foram realizados para explorar a relação de diversas variáveis ambientais nos padrões de distribuição destes cirripédios. Testamos também se as oscilações naturais na disponibilidade de alimento determinam padrões espaciais e temporais da qualidade da larva produzida e os efeitos da disponibilidade de alimento para as mães e para os seus descendentes na qualidade do estágio larval final deste organismo. Os resultados obtidos nessa tese apontam para a importância da disponibilidade de alimento na coluna d\'água em determinar padrões de abundância e tamanho dos organismos adultos, bem como a relação com o grau de exposição à ação de ondas na manutenção de populações adultas. Concluímos também que mudanças sazonais na produtividade primária tem um efeito na fecundidade e qualidade da larva produzida ao longo do ano por esses cirripédios. Finalmente pudemos demonstrar que pequenas alterações na quantidade de alimento fornecida à mães e larvas de Chthamalus são suficiente para provocar plasticidade de alguns tratos larvais importantes para os processos e sucesso do recrutamento destes organismos. / Spatial and temporal variability of larval supply can strongly influence the recruitment rates in populations of marine intertidal invertebrates, and thus determine the abundance and distribution patterns of adults. However, the behavior of larvae prior to settlement, and its physiological condition, may also play an important role. There are several factors that influence the physiological quality of a larva, one of them being maternal effects, that is, the way resources are allocated by mothers to produce their offspring, especially the way it affects fecundity. Another important factor is the trophic state of the environment where early stages develop into competent pre-final stages. However, little is known about the relationship between these two processes and if the natural variability of coastal conditions actually causes poorer quality in young performance and recruitment rates. In this study we analyzed the processes affecting embryonic and larval quality and if they are independent or interactive, and also if the environmental conditions along a subtropical coast can mediate trends in quality larvae to mesoscale and also determine sessile intertidal invertebrates distribution patterns. We used the barnacle Chthamalus bisinuatus as a biological model, and laboratory and field experiments were conducted to explore the relationship of various environmental variables in the patterns of distribution of these barnacles. We tested also if natural fluctuations in food availability determine spatial and temporal patterns of larvae quality produced and the effects of food availability for mothers and their descendants in the quality of the final larval stage of this organisms. The results obtained in this thesis point to the importance of the food availability in the water column in determining patterns of abundance and size of adult organisms, and the relationship with the degree of exposure to wave action in the maintenance of adult populations. We also conclude that seasonal changes in primary productivity has an effect on fecundity and quality of the larvae produced throughout the year by those barnacles. Finally we were able to demonstrate that small changes in the amount of food provided to mothers and larvae Chthamalus are enough to cause plasticity of some important larval traits which impacts the processes and success of recruitment in these organisms.

Scleractinian corals are the ‘engineers’ of tropical coral reef ecosystems. Their three-dimensional structure provides habitat for thousands of fish and invertebrate species. The persistence of corals is threatened by climate change. In this study I investigated if corals may be able to increase tolerance to ocean warming through developmental acclimation, i.e. if corals that experience warmer temperatures during embryonic and larval development are better able to cope with higher temperatures later in life. Larvae of the broadcast spawning coral Montastraea cavernosa were raised at ambient (29°C) and future projected ocean warming temperatures (+2°C, 31°C). After larval settlement, coral juveniles from each treatment were split and reared for two months at either current or +2°C conditions. Larvae reared at the warmer temperature had lower survival and displayed a smaller size at settlement. Juveniles that were in the warmer conditions had faster growth rates. Individuals raised during larval and juvenile stages at 31°C had faster growth rates than individuals only in the elevated temperature treatment after settlement, thus indicating that developmental acclimation may have occurred. However, the highest mortality also occurred in this treatment, therefore the growth results could also be explained by positive selection of the most thermally tolerant individuals. My results suggest that acclimation and/or directed selection may help corals withstand future rises in ocean temperature.

No description available.