How does rising atmospheric CO2 affect marine organisms?

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How Adult Oyster Exposure to Ocean Acidification Impacts the Response of Their Offspring to Elevated Atmospheric CO2
Parker, L.M., Ross, P.M., O'Connor, W.A., Borysko, L, Raftos, D.A. and Portner, H.-O. 2012. Adult exposure influences offspring response to ocean acidification in oysters. Global Change Biology 18: 82-92.

The authors write that studies on the impact of ocean acidification on marine organisms that have been conducted to date "have only considered the impacts on 'adults' or 'larvae', ignoring the potential link between the two life-history stages and the possible carry-over effects that may be passed from adult to offspring," citing the work of Dupont et al. (2010), Hendriks et al. (2010) and Kroeker et al. (2010).

What was done
To begin to fill this research void, Parker et al. placed adults of wild-collected and selectively-bred populations of the Sydney rock oyster (Saccostrea glomerata) - which they obtained at the beginning of reproductive conditioning - within seawater equilibrated with air of either 380 ppm CO2 (near-ambient) or 856 ppm CO2 (predicted for 2100 by the IPCC) that produced seawater pH values of 8.2 and 7.9, respectively, after which they measured the development, growth and survival responses of the two sets of larvae.

What was learned
The six scientists found that the larvae spawned from adults living in the "acidified" seawater were the same size as those spawned from adults living in near-ambient seawater; but they report that "larvae spawned form adults exposed to elevated CO2 were larger and developed faster." In addition, they say that "selectively bred larvae of S. glomerata were more resilient to elevated CO2 than wild larvae," noting that "measurement of the standard metabolic rate (SMR) of adult S. glomerata showed that at ambient CO2, SMR is increased in selectively bred compared with wild oysters," and that it is further increased "during exposure to elevated CO2."

What it means
Parker et al. say their findings suggest that "previous studies that have investigated the effects of elevated CO2 on the larvae of molluscs and other marine organisms [whose predecessors had not been exposed to elevated CO2] may overestimate the severity of their responses," concluding that the results of their work suggest that "marine organisms may have the capacity to acclimate or adapt to elevated CO2 over the next century."

Dupont, S., Dorey, N. and Thorndyke, M. 2010. What meta-analysis can tell us about vulnerability of marine biodiversity to ocean acidification? Estuarine, Coastal and Shelf Science 89: 182-185.

Hendriks, I.E., Duarte, C.M. and Alvarez, M. 2010. Vulnerability of marine biodiversity to ocean acidification: a meta-analysis. Estuarine, Coastal and Shelf Sciences 86: 157-164.

Kroeker, K.J., Kordas, R.L., Crim, R.N. and Singh, G.G. 2010. Meta-analysis reveals negative yet variable effects of ocean acidification on marine organisms. Ecology Letters 13: 1419-1434.

Reviewed 23 May 2012