How does rising atmospheric CO2 affect marine organisms?

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Effects of Ocean Acidification on Sediment Bacterial Communities
Kerfahi, D., Hall-Spencer, J.M., Tripathi, B.M., Milazzo, M., Lee, J. and Adams, J.M. 2014. Shallow water marine sediment bacterial community shifts along a natural CO2 gradient in the Mediterranean Sea off Vulcano, Italy. Microbial Ecology 67: 819-828.

The authors write that "covering around 70% of the earth, marine sediments play a major role in ecosystem processes and underpin carbon and nutrient cycling (Widdicombe et al., 2011)," due to the fact that "they are colonized by a vast, but unknown, diversity of microorganisms living in a variety of habitats (Munn, 2011)."

What was done
Hoping to get some idea about the sensitivity of these microorganisms to ocean acidification, Kerfahi et al. used 454 pyrosequencing of the V1 to V3 region of the 16S rRNA gene "to investigate the effect of a natural gradient in seawater pCO2 on sediment bacterial communities off Vulcano in the Mediterranean," where they "sampled the upper 2 cm of volcanic sand in three zones, ambient (median pCO2 419 µatm, minimum Ωarag 3.77), moderately CO2-enriched (median pCO2 592 µatm, minimum Ωarag 2.96), and highly CO2-enriched (median pCO2 1611 µatm, minimum Ωarag 0.35)."

What was learned
The six scientists determined that "the relative abundances of most of the dominant genera were unaffected by the pCO2 gradient." In fact, they actually found that "bacterial diversity increased toward higher pCO2."

What it means
"Overall," in the words of Kerfahi et al., these findings "support the view that globally increased ocean pCO2 will be associated with changes in sediment bacterial community composition but that most of these organisms are resilient."

Munn, C.B. 2011. Marine Microbiology: Ecology and Applications. Second Edition. Garland Science, New York, New York, USA.

Widdicombe, S., Spicer, J.I. and Kitidis, V. 2011. Effects of ocean acidification on sediment fauna. In: Gattuso, J.P. and Hansson, L. (Eds.). Ocean Acidification. Oxford University Press, Oxford, United Kingdom, pp. 176-191.

Reviewed 13 August 2014