Differences in larval acidification tolerance among populations of the eastern oyster, Crassostrea virginica

Abstract

The eastern oyster, Crassostrea virginica, is an ecologically and economically important species that is threatened by ongoing coastal ocean acidification. Oyster larvae are known to be more susceptible to acidification than either juvenile or adult life stages, but less is known about what levels of acidification induce a stress response and how this stress response changes with increasing acidification. Furthermore, little is known about population-level variability in acidification tolerance in C. virginica, making predictions of how this species will respond to future environmental scenarios difficult. To address these knowledge gaps, both whole animal and cellular metrics were used to quantify the acidification response of larvae produced by adults collected from Page Rock reef and Parrot's Rock reef, two spatially distinct reefs in adjacent tributaries of Chesapeake Bay. A comparison of Page Rock reef larvae among four acidification scenarios (pH 7.8, 7.5, 7.2, 7.0) revealed differences in shell length, total protein content, and triglyceride content, with growth increasingly impacted as acidification intensity increased. However, the sensitivity of these traits to acidification varied, where shell length was similarly impacted between pH 7.5 and 7.2, while protein and triglyceride content continued to decrease between these acidification scenarios. Triglyceride accumulation was most severely impacted under the lowest pH tested (pH 7.0), signaling that acidification could ultimately reduce the number of individuals successfully recruiting into the adult population if adequate energy stores cannot be accumulated for metamorphosis. A comparison of larvae between the two reefs at pH 7.8 and 7.2 revealed differences in survival, growth, and energy accumulation that suggest clear underlying physiological variations in larvae between reefs and unique sensitivities to acidification stress. These findings demonstrate that acidification tolerance within C. virginica can vary by population, which will have important implications for industry and conservation efforts as more resilient populations would make better candidates for future selective breeding efforts as well as restoration initiatives.