Environmental genomics approaches for the study of multiple stressors in freshwater ecosystems

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The anthropogenic pressures currently applied to aquatic habitats (increased metal loads, high concentrations of nutrients, increased acidity, accelerated introduction of invasive species) can generate extreme environmental conditions that can alter the supported communities and compromise the function of these ecosystems. Evaluating the impact of multiple stressors on aquatic ecosystems is particularly challenging due to the interactions amongst sources of stress and amongst the organisms themselves as well as the complex ecological and evolutionary dynamics that follow after stress. The long-term research objective of the proposed work is to advance new, integrative approaches for the study of multiple stressors in aquatic ecosystems. ***I propose to use a combination of experimental evolution (mutation accumulation and mesocosm experiments) and genomic approaches (transcriptomics, population genetics and metabarcoding) as well as Daphnia as a model organism to evaluate the responses of aquatic communities to environmental stressors. By using a long-term mutation accumulation experiment we plan to examine the global transcritional divergence patterns in mutation lines propagated under minimal selection and in isolates propagated under selection. This approach will allow us to provide insights into the evolutionary forces that shape gene expression. We will explore the extent to which environmental stressors (heavy metals) alter the mutation rate as well as the global transcriptional pattern. By using a large mesocosm experiment coupled with population genomics and metabarcoding approaches we will evaluate how genetic diversity and community composition changes during imposed environmental changes. We will explore the genetic changes at the population level that precede major changes to community composition. Moreover the mesocosm experiment will allow us to identify the genes important for adaptive responses to stressors. Jointly, these studies will provide unprecedented insights into the complex linkages between exposure to stressors and 1) the long-term effects on genome stability, 2) the global transcriptional pattern, 3) the changes in genetic diversity and community composition, 4) the capacity for rapid response, and ultimately 5) the long-term health of natural populations. ***This unique combination of experimental evolution and environmental genomics will allow our research group to investigate the ramifications of multiple stressors on the structural and functional attributes of aquatic ecosystems at a previously unattainable level of detail, control and replication. The proposed studies will also allow us to develop and test new ecological genomic approaches for the study of multiple stressors. The proposed projects provide an excellent opportunity for multidisciplinary and collaborative training at both graduate and undergraduate levels.