Juvenile Eastern Oysters More Resilient to Extreme Ocean Acidification than Their Mud Crab Predators

Ocean acidification is predicted to impair marine calcifiers' abilities to produce shells and skeletons. We conducted laboratory experiments investigating the impacts of CO2-induced ocean acidification (pCO2 = 478–519, 734–835, 8,980–9,567; Ωcalcite = 7.3–5.7, 5.6–4.3, 0.6–0.7) on calcification rates of two estuarine calcifiers involved in a classic predator-prey model system: adult Panopeus herbstii (Atlantic mud crab) and juvenile Crassostrea virginica (eastern oyster). Both oyster and crab calcification rates significantly decreased at the highest pCO2 level. Notably, however, oysters maintained positive net calcification rates in the highest pCO2 treatment that was undersaturated with respect to calcite, while mud crabs exhibited net dissolution (i.e., net loss of shell mass) in calcite-undersaturated conditions. Secondary electron imaging of oyster shells revealed minor microstructural alterations in the moderate-pCO2 treatment, and major microstructural and macrostructural changes (including shell dissolution, delamination of periostracum) in the high-pCO2 treatment. These results underscore the threat that ocean acidification poses for marine organisms that produce calcium carbonate shells, illustrate the strong biological control that some marine calcifiers exert over their shell-building process, and shows that ocean acidification differentially impacts the crab and oyster species involved in this classical predator-prey model system