How does rising atmospheric CO2 affect marine organisms?

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Acidification of the Small Larvae of a Large Tropical Marine Fish
Bignami, S., Sponaugle, S. and Cowen, R.K. 2013. Response to ocean acidification in larvae of a large tropical marine fish, Rachycentron canadum. Global Change Biology 19: 996-1006.

The authors write that "there is a critical need to understand the effects of acidification on the vulnerable larval stages of marine fishes, as there is a potential for large ecological and economic impacts on fish populations and the human economies that rely on them." And, therefore, they studied "the larvae of Rachycentron canadum (cobia), a large, highly mobile, pelagic-spawning, widely distributed species with a life history and fishery value contrasting other species studied to date."

What was done
As they describe it, Bignami et al. raised larval cobia through the first three weeks of ontogeny under conditions of predicted future ocean acidification to determine effects on somatic growth, development, swimming ability, swimming activity, and the formation of otoliths, which are structures of the inner ear that are used as gravity, balance, movement and directional indicators that have a secondary function in sound detection in higher marine vertebrates.

What was learned
The three U.S. researchers report finding that "cobia exhibited resistance to treatment effects on growth, development, swimming ability, and swimming activity at 800 and 2100 ľatm pCO2," while also finding that "these scenarios resulted in a significant increase in otolith size (up to 25% larger area)."

What it means
In the concluding words Bignami et al., "this study demonstrates that cobia is unlikely to experience a strong negative impact from CO2-induced acidification predicted to occur within the next several centuries," which consequence they speculate "may be due to the naturally variable environmental conditions this species currently encounters throughout ontogeny in coastal environments," which they further suggest "may lead to an increased acclimatization ability even during long-term exposure to stressors."

Reviewed 28 August 2013