How does rising atmospheric CO2 affect marine organisms?

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Effects of Ocean Acidification on Egg & Larval Stages of Baltic Cod
Frommel, A.Y., Schubert, A., Piatkowski, U. and Clemmesen C. 2013. Egg and early larval stages of Baltic cod, Gadus morhua, are robust to high levels of ocean acidification. Marine Biology 160: 1825-1834.

In spite of its predicted detrimental effects on calcifying organisms, the authors say that studies of possible impacts of ocean acidification [OA] on fish "remain scarce." While noting that "adults will most likely remain relatively unaffected by changes in seawater pH," they indicate that "early life-history stages are potentially more sensitive, due to the lack of gills with specialized ion-regulatory mechanisms." And, therefore, they focused their attention on the egg and early larval stages of Baltic cod (Gadus morhua), which they describe as "the commercially most important fish stock in the Baltic Sea."

What was done
Frommel et al. studied the effects of ocean acidification on a number of egg and larval properties of G. morhua "over the range of CO2 concentrations predicted in future scenarios for the Baltic Sea (from current values of 380 ľatm up to 3,200 ľatm CO2water)," and this they did, both "with and without the combination of increasing temperature."

What was learned
The four German scientists report that "no effect on hatching, survival, development, and otolith size was found at any stage in the development of Baltic cod," where "in situ levels of pCO2 are already at levels of 1,100 ľatm with a pH of 7.2." In fact, they say their data showed that "the eggs and early larval stages of Baltic cod seem to be robust to even higher levels of OA (3,200 ľatm), indicating an adaptational response to CO2."

What it means
In the concluding sentence of their revealing paper, Frommel et al. suggest that "since the Baltic Sea is naturally high in pCO2, its fish stocks may be adapted to conditions predicted in ocean acidification scenarios for centuries to come."

Reviewed 25 December 2013