Species and Population Differences in Responses to Ocean Acidification of Two Western North Atlantic Flatfishes

Tolerances of different species and populations to elevated levels of pCO₂ and temperature may be associated with early life-history strategies, habitat use, and parental exposure.  In five experiments we exposed gametes, embryos, and larvae of several populations of winter flounder, Pseudopleuronectes americanus, and one of summer flounder, Paralichthys dentatus, to multiple pCO₂ and temperature environments. Winter flounder spawn benthic eggs typically in estuaries of the US Mid-Atlantic Bight (MAB) to Gulf of Maine (GOM) so their early life-stages are exposed to variable water chemistry. We predicted they would tolerate acidic conditions better than summer flounder which spawn buoyant eggs in relatively stable shelf waters of the MAB.  Overall, winter flounder displayed increased fertilization success and embryonic survival with elevated pCO₂ and colder temperature.  The responses of winter flounder varied with the source of adults (GOM versus MAB).  Offspring of GOM origin were more tolerant to acidity than those from the MAB, but less tolerant to warmer water.  Summer flounder exhibited reduced fertilization and embryonic survival with elevated pCO₂ and colder temperature.  Population and species differences in early life-stage responses to elevated pCO₂ may influence the adaptation potential and persistence of these species at predicted levels of near-future climate change.