Short- and long-term consequences of larval stage exposure to constantly and ephemerally elevated carbon dioxide for marine bivalve populations

Gobler, C. J.; Talmage, S. C.

While larval bivalves are highly sensitive to ocean acidification, the basis for this sensitivity and the longer-term implications of this sensitivity are unclear. Experiments were performed to assess the short-term (days) and long-term (months) consequences of larval stage exposure to varying CO 2 concentrations for calcifying bivalves. Higher CO 2 concentrations depressed both calcification rates assessed using 45Ca uptake and RNA : DNA ratios in Mercenaria mercenaria and Argopecten irradians larvae with RNA : DNA ratios being highly correlated with larval growth rates ( r2>0.9). These findings suggested that high CO 2 has a cascading negative physiological impact on bivalve larvae stemming in part from lower calcification rates. Exposure to elevated CO 2 during the first four days of larval development significantly depressed A. irradians larval survival rates, while a 10-day exposure later in larval development did not, demonstrating the extreme CO 2 sensitivity of bivalve larvae during first days of development. Short- (weeks) and long-term (10 month) experiments revealed that individuals surviving exposure to high CO 2 during larval development grew faster when exposed to normal CO 2 as juveniles compared to individuals reared under ambient CO 2 as larvae. These increased growth rates could not, however, overcome size differences established during larval development, as size deficits of individuals exposed to even moderate levels of CO 2 as larvae were evident even after 10 months of growth under normal CO 2 concentrations. This "legacy effect" emphasizes the central role larval stage CO 2 exposure can play in shaping the success of modern-day bivalve populations.

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Gobler, C. J. / Talmage, S. C.: Short- and long-term consequences of larval stage exposure to constantly and ephemerally elevated carbon dioxide for marine bivalve populations. 2013. Copernicus Publications.

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