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Ocean pH Tolerance in Two Important Antarctic Invertebrates
Reference
Ericson, J.A., Lamare, M.D., Morley, S.A. and Barker, M.F. 2010. The response of two ecologically important Antarctic invertebrates (Sterechinus neumayeri and Parborlasia corrugatus) to reduced seawater pH: effects on fertilization and embryonic development. Marine Biology 157: 2689-2702.

Background
The authors write that in polar latitudes "the effects of changing pCO2 and pH on gametes may be influenced by the carbonate chemistry of cold water, such as the already higher pCO2 and lower seawater pH," and they say "it has also been predicted that ocean acidification effects on organisms may be more apparent and appear earliest in polar waters."

What was done
To explore this situation further, Ericson et al. "investigated the effects of present-day pH 8.0, predicted ocean surface pH for the years 2100 and 2300 (pH 7.7 and pH 7.3, respectively) and an extreme pH (pH 7.0) on fertilization and embryogenesis in the Antarctic nemertean worm Parborlasia corrugatus and sea urchin Sterechinus neumayeri."

What was learned
The four researchers report that "fertilization success was not affected by pH in P. corrugatus across a range of sperm concentrations," and that "fertilization success in S. neumayeri declined significantly in pH 7.0 and 7.3 seawater, but only at low sperm concentration." In addition, they say that "seawater pH had no effect on the rate of egg cleavage in S. neumayeri, or the proportion of abnormal embryos 1-day post-fertilization," and that "P. corrugatus embryogenesis was also relatively robust to pH changes, with a significant effect detected only when the seawater pH was decreased to 7.0"

What it means
Ericson et al. conclude, "as in a number of other studies (see reviews by Byrne et al., 2010; Dupont et al., 2010), that gametes appeared relatively robust to pH change, especially to changes within the range predicted for the near future (i.e. a decrease of 0.3-0.5 pH units)," and they state that their initial findings "do not support a view that polar species are more affected by lowered pH compared with temperate and tropical counterparts (as has also been shown for the later developmental stages of S. neumayeri (Clark et al., 2009))."

In addition, we note that the work of Tans (2009) suggests that ocean pH reduction due to rising atmospheric CO2 will never drop by even the smallest amount employed by Ericson et al. in their study (i.e., 0.3). And, thus, another climate-alarmist contention continues to look just a bit too alarming to be true.

References
Byrne, M., Soars, N., Ho, M.A., Wong, E., McElroy, D., Selvakumaraswamy, P., Dworjanyn, S.A. and Davis, A.R. 2010. Fertilization in a suite of coastal marine invertebrates from SE Australia is robust to near-future ocean warming and acidification. Marine Biology 157: 2061-2069.

Clark, D., Lamare, M and Barker, M. 2009. Response of sea urchin pluteus larvae (Echinodermata: Echinoidea) to reduced seawater pH: a comparison among a tropical, temperate, and a polar species. Marine Biology 156: 1125-1137.

Dupont, S., Ortega-Martinez, O. and Thorndyke, M. 2010. Impact of near-future ocean acidification on echinoderms. Ecotoxicology 19: 449-462.

Tans, P. 2009. An accounting of the observed increase in oceanic and atmospheric CO2 and an outlook for the future. Oceanography 22: 26-35.

Reviewed 25 May 2011