| Summary: | The Pacific Oyster (Crassostrea gigas) is one of the most economically and ecologically significant shellfish species worldwide. In the Pacific Northwest United States (PNW), the sustainability oyster stocks is increasingly threatened by ocean acidification (OA), which has had significant negative effects on the aquaculture industry in this region over the last decade. Currently, little is known with regards to stock-based differences in larval fitness for PNW populations of C. gigas in ambient or high pCO2 conditions. Furthermore, no studies have been performed that evaluate the genetic consequences of larval rearing in acidified seawater for Pacific oysters. Here I examined genetic components of larval fitness traits, both in ambient seawater as well as simulated OA conditions. In Chapter 2 my co-authors and I conducted two experiments to compare the relative fitness of larvae from selectively bred aquaculture stocks to those spawned from a naturalized source of broodstock in Willapa Bay, WA. We reared genetically diverse pools of larvae from each group in ambient (~400 μatm) and high (~1600 μatm) pCO2 seawater for 22-24 days from fertilization through settlement to juvenile stage. Overall, we found that the impacts of high pCO2 seawater on larval phenotypes were heterogeneous across larval developmental stages and variable between the two experiments. Nevertheless, larvae from selectively bred lines had consistently higher survival and greater developmental success through settlement than those from naturalized stocks across both conditions and experiments. In Chapter 3 we analyzed the overall changes in genetic composition of each larval pool created in the first experiment. We found an abundance of loci with significantly distorted allele frequencies across larval development, nearly all of which were specific to each broodstock type. There were additional genetic changes owing to high pCO2 culture that, also, were largely unique to each parental group. Overall, larvae from selectively bred stocks had ...
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