How does rising atmospheric CO2 affect marine organisms?

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Sea Anemones and Microbes in a CO2-Vent-Induced pH Gradient
Meron, D., Buia, M.-C., Fine, M. and Banin, E. 2013. Changes in microbial communities associated with the sea anemone Anemonia viridis in a natural pH gradient. Microbial Ecology 65: 269-276.

The authors write that "ocean acidification is an ecological stressor that influences not only the organism itself but may also lead to profound ecological shifts in the surrounding ecosystem." And they therefore say it is crucial "to examine these changes in the field (in situ experiments)," which allows for "the incorporation of other environmental factors that exist in the field but cannot be replicated in the laboratory."

What was done
Meron et al. studied the physiology of the sea anemone Anemonia viridis, which grows naturally along a CO2-vent-induced pH gradient in the vicinity of Ischia, Italy, as well as the nature of the associated microbial community (bacteria and endosymbiotic Symbiodinium), focusing on two specific locations that could be characterized as ambient (pCO2 330 ppm, pH 8.1) and very CO2-enriched (pCO2 9341 ppm, pH 7.0).

What was learned
The four researchers determined that although reduction in pH was seen to have had an impact on the composition and diversity of the anemones' associated microbial communities, "no significant changes were observed in A. viridis physiology, and no microbial stress indicators (i.e., pathogens, antibacterial activity, etc.) were detected."

What it means
In commenting on their findings, Meron et al. state that "in light of these results, it appears that elevated CO2 does not have a negative influence on A. viridis that live naturally in the [very CO2-enriched] site." And they say that "this suggests that natural long-term exposure and dynamic diverse microbial communities may contribute to the acclimation process of the host in a changing pH environment."

Reviewed 10 July 2013