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Sub-Antarctic Sea Urchin Larval Responses to Lower Seawater pH
Catarino, A.I., De Ridder, C., Gonzalez, M., Gallardo, P. and Dubois, P. 2012. Sea urchin Arbacia dufresnei (Blainville 1825) larvae response to ocean acidification. Polar Biology 35: 455-461.

The authors write that "increased atmospheric CO2 emissions are inducing changes in seawater carbon chemistry, lowering its pH, decreasing carbonate ion availability and reducing calcium carbonate saturation state," which phenomenon (known as ocean acidification) is said by them to be "happening at a faster rate in cold regions, i.e., polar and sub-polar waters," where marine biologists are beginning to look for early indications of what may be in store for earth's many calcifying forms of sea life, as the declining trend in seawater pH continues.

What was done
Catarino et al. studied the development of larvae produced by adults of the sea urchin Arbacia dufresnei - which they collected from a sub-Antarctic population in the Straits of Magellan near Punta Arenas, Chile - when immersed in high (8.0), medium (7.7) and low (7.4) pH seawater.

What was learned
The five scientists state that "the proportion of abnormal larvae did not differ according to [pH] treatment," with the result that although "lower pH induced a delay in development" - which has also been noted by Dupont et al. (2010) - it "did not increase abnormality." They additionally indicate that "even at calcium carbonate saturation states <1, skeleton deposition occurred," and they further note in this regard that specimens of Heliocidaris erythrogramma also "seem not to be affected by a pH decrease (until 7.6)," citing Byrne et al. (2009a,b), while likewise noting that the Antarctic Sterechinus neumayeri is also thought to be "more robust to ocean acidification than tropical and temperate sub-tidal species," citing Clark et al. (2009) and Ericson et al. (2010).

What it means
The findings of Catarino et al., as well as those of the other researchers they cite, suggest that "polar and sub-polar sea urchin larvae can show a certain degree of resilience to acidification." And they conclude that because of this fact, A. dufresnei has the potential to "migrate and further colonize southern regions."

Bryne, M., Ho, M., Selvakumaraswamy, P., Nguyen, H.D., Dworjanyn, S.A. and Davis, A.R. 2009a. Temperature, but not pH, compromises sea urchin fertilization and early development under near-future climate change scenarios. Proceedings of the Royal Society B 276: 1883-1888.

Bryne, M., Soars, N., Selvakumaraswamy, P., Dworjanyn, S.A. and Davis, A.R. 2009b. Sea urchin fertilization in a warm, acidified and high pCO2 ocean across a range of sperm densities. Marine Environmental Research 69: 234-239.

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

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.

Reviewed 6 June 2012