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A Limited Response of a Deep-sea Coral to Ocean Acidification

Paper Reviewed
Gammon, M.J., Tracey, D.M., Marriott, P.M., Cummings, V.J. and Davy, S.K. 2018. The physiological response of the deep-sea coral Solenosmilia variabilis to ocean acidification. PeerJ 6: e5236, doi: 10.7717/peerj.5236.

According to Gammon et al. (2018), "scleractinian corals in deep, cold-water environments are predicted to be affected by global change, such as ocean acidification (OA), much sooner than corals in surface waters of more temperate regions." Yet they also note that "the response of deep-sea corals to OA, and resulting low carbonate saturation levels, is poorly understood." And so the five marine researchers set out to remedy this situation by investigating the long-term (one-year) response of OA on a long-lived, somewhat fragile scleractinian coral species (Solenosmilia variabilis) from New Zealand.

To do so they collected live colonies from the deep ocean east of New Zealand and maintained them in a controlled-laboratory setting at the National Institute of Atmospheric Research's Marine Environmeental Manipulation Facility in Wellington under ambient pH (7.88; pCO2 of 519) or reduced pH (7.65; pCO2 of 920, ΩAR= 0.69). After 12 months in these seawater conditions they conducted a number of physiological measurements.

And what did those measurements reveal? Gammon et al. report that (1) "the colonies were generally robust to OA conditions (there was no mortality)," (2) there was "no treatment effect on mortality of polyps or linear growth trends," and (3) "respiration rates also varied independently of pH." They only potentially adverse consequence was a slight difference in color loss ("a difference of 5.28% between the percentage of initial color remaining between treatment and control groups"). However, the researchers note that such color loss "is not surprising given that deep-sea corals are difficult to maintain in a healthy state in aquaria; indeed, to our knowledge, S. variabilis has never previously been maintained for more than a few weeks in this state."

All in all, given the limited response to OA displayed by S. variabilis, it would appear this deep-sea coral is somewhat resilient to OA.

Posted 23 March 2020