Effects of Ocean Acidification on Early Development of Sea Urchins

According to Moulin et al. (2011), "sea urchins are key species in many coastal ecosystems, being important grazers, and the sustainability of their populations is vital (Paine, 1966; Harrold and Pearse, 1987; Leblanc et al., 2005)." And they further note, in this regard, that early development stages of marine invertebrates, such as sea urchins, "are generally the most sensitive life phases to environmental stresses (Portner and Farrell, 2008; Melzner et al., 2009; Dupont et al., 2010)."

Focusing on this sensitive stage of life, Moulin et al., as they describe it, "studied the sea urchin Paracentrotus lividus, an important grazer species (Bulleri et al., 1999) with a broad distribution and that can be found in the whole Mediterranean and North Atlantic coasts of Europe (from Morocco to Scotland), inhabiting intertidal rock pools, seagrass meadows and shallow subtidal shores (Boudouresque and Verlaque, 2001)," where their strategy was "to compare the effect of pH on the progeny of individuals collected from the same shore, i.e., same population, but from distinct tide pools: one where night pH was significantly reduced and the other where this decline was not so important." And what did they find?

The four Belgian researchers report that the pH of coastal seawater at the site they studied (Aber, Crozon peninsula, southern Brittany, France) was 8.14; but they say that at the end of the night low tides, tide pools 1 (subtidal) and 2 (intertidal) had pH values of, respectively, 7.8 and 7.4. Under these conditions, they detected "no significant difference in gonad maturity between individuals from the two tide pools," and they report that "the offspring of sea urchins from the tide pool with higher pH decrease (tide pool 2) showed a better resistance to acidification at pH 7.4 than that of sea urchins from the tide pool with low pH decrease (tide pool 1) in terms of fertilization, viz. a reduction of over 30% [for tide pool 1] compared to about 20% for tide pool 2."

Commenting on their findings, Moulin et al. conclude that "sea urchins inhabiting stressful intertidal environments produce offspring that may better resist future ocean acidification." And they add that the fact that "the fertilization rate of gametes whose progenitors came from the tide pool with higher pH decrease was significantly higher," suggests "a possible acclimation or adaptation of gametes to pH stress."

Additional References
Boudouresque, C.F. and Verlaque, M. 2001. Ecology of Paracentrotus lividus. In: Lawrence, J.M. (Ed.). Edible Sea Urchins: Biology and Ecology. Elsevier, Amsterdam, the Netherlands, pp. 177-216.

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

Harrold, C. and Pearse, J.S. 1987. The ecological role of echinoderms in kelp forests. In: Jangoux, M. and Lawrence, J.M. (Eds.). Echinoderm Studies 2. Balkema, Rotterdam, the Netherlands.

Leblanc, N., Letourneur, Y., Ruitton, S. and Marschal, C. 2005. Impacts a court terme de la concentration experimentale d'oursins (Paracentrotus lividus) sur les autres compartiments benthiques de l'ecosysteme rocheux infralittoral mediterraneen: mise en evidence "d'effets-cascade"? Journal de Recherche Oceanographique 30: 12-23.

Melzner, F., Gutowska, M.A., Langenbuc, M., Dupont, S., Lucassen, M., Thorndyke, M.C., Bleich, M. and Portner, H.-O. 2009. Physiological basis for high CO₂ tolerance in marine ectothermic animals: pre-adaptation through lifestyle and ontogeny? Biogeosciences 6: 2313-2331.

Paine, R.T. 1966. Food web complexity and species diversity. American Naturalist 100: 65-75.

Portner, H.O. and Farrell, A.P. 2008. Physiology and climate change. Science 322: 690-692.