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Collaborative Research: Transgenerational phenotypic and genomic responses of marine copepods to the interactive effects of temperature and CO2 Hans G. Dam, Hannes Baumann and Michael Finiguerra, University of Connecticut Melissa Pespeni, University of Vermont PROJECT SUMMARY Overview: This project seeks novel and fundamental knowledge and understanding of the response of copepods to simultaneous conditions of warming and ocean acidification, and the roles of genetic and epigenetic adaptation to thermal and CO2 stress. The main goals of the project are : 1) To test the simultaneous effects of temperature and CO2 under current and future conditions on life history traits, throughout the life cycle, of two keystone copepod species, Acartia tonsa (warm-adapted) and Acartia hudsonica (cold-adapted). 2) To test for adaptive capacity of both copepod species to a warmer and CO2-richer ocean. 3) To measure the genetic and epigenetic changes across multiple generations of experimental selection in future conditions in both copepod species, and to identify the genes and pathways responding to selection. Factorial (2X2) design experiments, which include mean current and projected temperature and CO2 conditions, will determine the respective roles of temperature and CO2 and their combinations on life history traits of both copepod species. Traits to be measured include egg production and hatching, survivorship from egg to adults, development time, and adult size and survival. This information will be used to estimate Darwinian fitness and to determine which stages of the copepod life cycle are most sensitive to individual or simultaneous stress conditions of temperature and CO2. The mechanisms of copepod adaptation will be identified and the role of transgenerational plasticity will be characterized through multigenerational selection experiments (> 10 generations for each species). Changes in allele and epi-allele frequency across the generations will be measured in all four conditions of the factorial design to quantify the relative contributions of genetic and epigenetic change in the evolution of critical physiology and life history traits in response to greenhouse climate conditions. Intellectual Merit: The ocean is predicted to become warmer and CO2-richer (higher pCO2 and lower pH) within a century. These environmental changes are occurring at unprecedented rates, and their consequences on populations of marine organisms are neither fully known nor understood. Hence, the ability to forecast the fate of populations faced with rapid environmental change is severely hampered at the moment, particularly by a paucity of experimental work that considers transgenerational plasticity. This project will determine, for the first time, how two closely related species of copepods (the most abundant animals in the oceans) with different potential for evolutionary thermal adaptation will respond to the interactive effects of warming and acidification, and whether these effects are mitigated by genetic or epigenetic adaptation. The proposed work, which combines measurements of phenotypic, genetic and epigenetic responses to global change conditions across multiple generations, is likely to provide novel insights into adaptation to thermal- and hypercapnia-related stress, and emerging properties that lead to adaptability. Broader Impacts: The outcomes of the work will have societal relevance by meeting one of the priority areas for marine ecosystem management: To gather and synthesize information on how systems are changing and on the drivers of these changes, especially over long time scales. In addition, the outcomes of the project could be used to parameterize the zooplankton component of mechanistic models or bioclimatic envelope models that scale up responses to warming and ocean acidification from organisms to ecosystems.