How does rising atmospheric CO2 affect marine organisms?

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Mussels Flex Their Muscles when Temperature & OA Both Increase

Paper Reviewed
Kroeker, K.J., Gaylord, B., Hill, T.M., Hosfelt, J.D., Miller, S.H. and Sanford, E. 2014. The role of temperature in determining species' vulnerability to ocean acidification: A case study using Mytilus galloprovincialis. PLOS ONE 9: e100353.

Writing as background for their work, Kroeker et al. (2014) say "there is considerable concern regarding potential synergistic effects among multiple environmental changes, where the combined effect on a species of two or more drivers is worse than would be expected from a strictly additive influence of the separate factors." On the other hand, they indicate that research has shown that "the presence of a second driver can also offset or lessen the effects of another stressor," citing Crain et al. (2008). And, therefore, they set about to determine what happens to the bay mussel Mytilus galloprovincialis when it is simultaneously exposed to both ocean acidification and warming. The six scientists accomplished this objective by measuring "the growth and shell accretion of M. galloprovincialis in the laboratory in a factorial combination of low and high pCO2 (400 and 1200 µatm CO2(atm), respectively) and a range of temperatures (12, 14, 16, 18, 20 and 24°C) over a period of one month." And what did they thereby find?

Kroeker et al. report that "although high CO2 significantly reduced mussel growth at 14°C, this effect gradually lessened with successive warming to 20°C, illustrating how moderate warming can mediate the effects of OA through temperature's effects on both physiology and seawater geochemistry." In addition, they found that "the mussels grew thicker shells in warmer conditions independent of CO2 treatment," and that "together, these results highlight the importance of considering the physiological and geochemical interactions between temperature and carbonate chemistry," especially when assessing a species vulnerability to OA.

"Importantly," as they thus conclude, "our results suggest that M. galloprovincialis may be able to tolerate increasing pCO2 and decreasing aragonite saturation state across the wide range of temperatures they naturally experience in the field, with moderate warming offsetting potential reductions in growth associated with OA."

Crain, C.M., Krocker, K. and Halpern, B.S. 2008. Interactive and cumulative effects of multiple human stressors in marine systems. Ecology Letters 11: 1304-1315.

Posted 9 December 2014