Acidified Seawater's Effects on Coral Larvae and Polyps
Suwa, R., Nakamura, M., Morita, M., Shimada, K., Iguchi, A., Sakai, K. and Suzuki, A. 2010. Effects of acidified seawater on early life stages of scleractinian corals (Genus Acropora). Fisheries Science 76: 93-99.
Results indicated that "A. digitifera larval survival rate did not differ significantly among pH treatments," and the graphs of their data indicate that survivorship in A. tenuis was actually about 18.5% greater in the lowest pH (highest CO2) treatment than in the ambient seawater treatment. At the end of the subsequent ten-day study, however, polyp size was reduced in the lowest pH treatment, but by only about 14%, which is not too bad for an atmospheric CO2 concentration in the range of 2115-3585 ppm. And in the A. tenuis coral, this reduction in individual size was more than compensated by the even greater percentage increase in survivorship. In addition, after only four days of being exposed to the zooxanthellae derived from giant clams, all polyps in all treatments had acquired a full complement of the symbiotic zooxanthella.
In discussing their findings, the seven scientists say they indicate that "the survival of coral larvae may not be strongly affected by pH change," or "in other words," as they continue, "coral larvae may be able to tolerate ambient pH decreases of at least 0.7 pH units," which, in fact, is something that will likely never occur, as it implies atmospheric CO2 concentrations in the range of 2115 to 3585 ppm. In addition, if such high concentrations ever were to occur, they would be a long, long time in coming, giving corals far more than sufficient time to acclimate -- and even evolve (Idso and Idso, 2009) -- to adequately cope with the slowly developing situation.
Idso, C.D. and Idso, S.B. 2009. CO2, Global Warming and Species Extinctions: Prospects for the Future. Vales Lake Publishing, LLC, Pueblo West, Colorado, USA, 132 p.