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Likely Responses of Gorgonian Octocorals to Ocean Acidification

Paper Reviewed
Gomez, C.E., Paul, V.J., Ritson-Williams, R., Muehllehner, N., Langdon, C. and Sanchez, J.A. 2015. Responses of the tropical gorgonian coral Eunicea fusca to ocean acidification conditions. Coral Reefs 34: 451-460.

Noting that "octocorals deposit high-magnesium calcite in their skeletons," and that "according to different models, they could be more susceptible to the depletion of carbonate ions than either calcite or aragonite-depositing organisms," Gomez et al. (2015) conducted an experiment to see if this assumption was correct or not, wherein they investigated the response of the gorgonian coral Eunicea fusca to a range of CO2 concentrations stretching from 285 to 4,568 ppm (a pH range of 8.1 to 7.1) over a 4-week period.

This work revealed, in the words of the six scientists, that "growth and calcification did not stop in any of the concentrations of pCO2." And this finding led them to tentatively conclude that "tropical octocorals appear to have the capacity to resist the future levels of ocean acidification expected to occur during this century as has been proposed by other studies," specifically citing in this regard those of Gabay et al. (2013, 2014) and Inoue et al. (2013). In fact, they indicate that already "in some shallow reefs, octocorals are becoming extremely abundant," serving as "possible natural examples of the outcome of ocean acidification," further citing Manzello (2010).

Based on this growing body of evidence, therefore, Gomez et al. conclude their report by noting that the findings of this body of research is "especially important because gorgonian corals form complex structures that provide unique habitat for different organisms, including refugia for recruitment, growth and reproduction," additionally citing Sanchez et al. (1998), Goh et al. (1999) and Nagelkerken et al. (2000).

References
Gabay, Y., Benayahu, Y. and Fine M. 2013. Does elevated pCO2 affect reef octocorals? Ecology and Evolution 3: 465-473.

Gabay, Y., Fine, M., Barkay, Z. and Benayahu, Y. 2014. Octocoral tissue provides protection from declining oceanic pH. PLoS One 9: e91553.

Goh, N.K., Peter, K.L. and Chou, L. 1999. Notes on the shallow water gorgonian-associated fauna on coral reefs in Singapore. Bulletin of Marine Science 655: 259-282.

Inoue, S., Kayanne, H., Yamamoto, S. and Kurihara, H. 2013. Spatial community shift from hard to soft corals in acidified water. Nature Climate Change 3: 683-687.

Nagelkerken, I., Dorenbosch, M., Verberk, W.C.E.P., Moriniere, E.C.D.L. and Velde, G.V.D. 2000. Importance of shallow-water biotopes of a Caribbean bay for juvenile coral reef fishes: patterns in biotope association, community structure and spatial distribution. Marine Ecology Progress Series 202: 175-192.

Sanchez, J., Zea, S. and Diaz, J. 1998. Patterns of octocoral and black coral distribution in the oceanic barrier reef-complex of Providencia Island, Southwestern Caribbean. Caribbean Journal of Science 34: 250-264.

Posted 19 August 2015