Influence of Early Life-History Strategies on the Responses of Two Western North Atlantic Flatfishes to Ocean Acidification

Recent studies reveal species and life-stages of finfish vary in their responses to changing ocean chemistry. Tolerances of species to elevated levels of pCO₂ may be associated with early life-history strategies, habitat use, and parental exposure. In four experiments over two years we exposed winter flounder, Pseudopleuronectes americanus, and summer flounder, Paralichthys dentatus, to multiple, constant pCO₂ and temperature levels at various life-stages (gametes, embryos, and larvae up to 6-wk post hatch). Winter flounder spawn in Northeast USA estuaries, their eggs adhere to substrates, and their early life-stages are exposed to variable water chemistry. Based on these life-history and habitat properties, winter flounder may be more tolerant of water acidity variations than summer flounder which spawn in Northeast USA continental shelf waters that are relatively more stable. Our results suggest that winter flounder gametes and embryos are more tolerant than those of summer flounder to elevated pCO₂. Winter flounder larvae, however, exhibited impaired condition and survival. Summer flounder had reduced fertilization and lower survival during the embryonic period when reared at elevated pCO₂ levels. Analyses of morphology, biochemical condition, and histological features of larvae are underway for purposes of evaluating sublethal responses later in larval life.