Physiological response and resilience of early life-stage Eastern oysters (Crassostrea virginica) to past, present and future ocean acidification

The Eastern oyster, Crassostrea virginica (Gmelin, 1791), is the second most valuable bivalve fishery in the USA and is sensitive to high levels of partial pressure of CO2 (pCO(2)). Here we present experiments that comprehensively examined how the ocean's past, present and projected (21st and 22nd centuries) CO2 concentrations impact the growth and physiology of larval stages of C. virginica. Crassostrea virginica larvae grown in present-day pCO(2) concentrations (380 MU atm) displayed higher growth and survival than individuals grown at both lower (250 mu atm) and higher pCO(2) levels (750 and 1500 mu atm). Crassostrea virginica larvae manifested calcification rates, sizes, shell thicknesses, metamorphosis, RNA: DNA ratios and lipid contents that paralleled trends in survival, with maximal values for larvae grown at 380 mu atm pCO(2) and reduced performance in higher and lower pCO(2) levels. While some physiological differences among oysters could be attributed to CO2-induced changes in size or calcification rates, the RNA: DNA ratios at ambient pCO(2) levels were elevated, independent of these factors. Likewise, the lipid contents of individuals exposed to high pCO(2) levels were depressed even when differences in calcification rates were considered. These findings reveal the cascading, interdependent impact that high CO2 can have on oyster physiology. Crassostrea virginica larvae are significantly more resistant to elevated pCO(2) than other North Atlantic bivalves, such as Mercenaria mercenaria and Argopecten irradians, a finding that may be related to the biogeography and/or evolutionary history of these species and may have important implications for future bivalve restoration and aquaculture efforts.