| Summary: | Thesis (Master's)--University of Washington, 2018 Marine calcifying invertebrates must be capable of acclimating or adapting to adverse carbonate conditions in order to withstand current and projected ocean acidification (OA). For some species, parental exposure to elevated CO2 during gametogenesis may alleviate the detrimental effects of OA on larval and juvenile offspring, through transgenerational phenotypic plasticity and/or rapid selection for beneficial genotypes. Whether these patterns persist in offspring into adulthood, or across multiple generations, remains largely unknown. In a previous study by our lab group, pre-exposure of G0 adult Pacific oyster, Crassostrea gigas, to 1977 μatm pCO2 prior to spawning was found to enhance the growth and survivorship of G1 larval and juvenile offspring at ambient pCO2 levels, but did not buffer offspring from acute, negative OA effects. In this study, we assessed performance of offspring at adulthood, and reared a subsequent G2 generation at two CO2 levels (494 and 1601 μatm). G1 adults from CO2-exposed parents experienced reduced shell and somatic growth compared to controls, with no evidence of adaptive transgenerational effects. G2 larvae were smaller and had higher rates of mortality and shell deformities under OA conditions, though transgenerational exposure in grandparents or parents appeared to partially alleviate the effects observed at elevated pCO2 on larvae with no history of exposure. We found evidence of maternal and paternal genetic variation in reproductive success at both high and low pCO2 that suggests that both selection and phenotypic plasticity underlie transgenerational effects of OA on G1 and G2 oysters. More broadly, our results highlight the utility of multigenerational studies in providing a more accurate measure of populations’ ability to respond to OA.
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