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Antarctic Sea Urchins in an Imagined Acidified and Warmed Ocean

Paper Reviewed
Kapsenberg, L. and Hofmann, G.E. 2014. Signals of resilience to ocean change: high thermal tolerance of early stage Antarctic sea urchins (Sterechinus neumayeri) reared under present-day and future pCO2 and temperature. Polar Biology 37: 967-980.

In a study published in the journal Polar Biology, two researchers from the University of California Santa Barbara - Lydia Kapsenberg and Gretchen E. Hofmann - set out to investigate whether specimens in the early developmental stages of the Antarctic sea urchin Sterechinus neumayeri would be able to survive and reach maturity under future conditions of global warming and ocean acidification. This they did by spawning the species in their laboratory and raising early developmental states (EDSs) of it - blastula, gastrula, prism and 4-arm echinopluteus - under ambient (-0.7°C, 400 µatm pCO2) and future (+2.6°C, 650 and 1,000 µatm pCO2), after which they exposed specimens of the four EDSs to a one-hour-long acute heat stress that reached as high as 25°C, at the end of which they assessed the urchins' degrees of survivorship.

When all was said and done, the two biologists were able to report that "all EDSs survived temperatures that greatly exceeded their average habitat temperature of -1.9°C." And they also found that S. neumayeri EDSs reared at -0.7°C "were extremely robust to pCO2" and that "no pCO2 effect was observed in the survivorship assays," which led them to suggest that "S. neumayeri EDSs may be more physiologically tolerant of future conditions than previously thought," additionally citing Byrne et al. (2013) in this regard.

In further discussing their findings, Kapsenberg and Hofmann state that "S. neumayeri may already harbor some genetic plasticity that allows EDSs to tolerate future ocean change, at least to some degree." And they thus suggest that "as the ocean changes, new selection forces will act on the existing genetic structure," and that "individuals will be exposed to slowly changing environments which could enhance benefits of existing physiological plasticity," such as those they observed.

Continuing on, the two researchers say "it is significant that some studies show that traits of resilience are heritable (Sunday et al., 2011; Kelly et al., 2013) and local adaptation likely plays a strong role (Pespeni et al., 2013; Schaum et al., 2013)," such that "a high degree of present-day physiological plasticity and genetic variability may facilitate adaptation and long-term tolerance of future conditions."

In concluding, and in light of these several observations, Antarctic sea urchins would appear to be well-equipped to handle the two environmental threats - ocean acidification and warming - about which many people seem most concerned.

References
Byrne, M., Ho, M., Koleits, L., Price, C., King, C., Virtue, P., Tilbrook, B and Lamare, M. 2013. Vulnerability of the calcifying larval stage of the Antarctic sea urchin Sterechinus neumayeri to near-future ocean acidification and warming. Global Change Biology 19: 2264-2275.

Kelly, M.W., Padilla-Gamino, J.L. and Hofmann, G.E. 2013. Natural variation and the capacity to adapt to ocean acidification in the keystone sea urchin Strongylocentrotus purpuratus. Global Change Biology 19: 2536-2546.

Pespeni, M.H.,Sanford, E., Gaylord, B., Hill, T.M., Hosfelt, J.D., Jaris, H.K., LaVigne, M., Lenz, E.A., Russell, A.D. and Young, M.K. 2013. Evolutionary change during experimental ocean acidification. Proceedings of the National Academy of Sciences USA 110: 6937-6942.

Schaum, E., Rost, B., Millar, A.J. and Collins, S. 2013. Variation in plastic responses to ocean acidification in a globally distributed picoplankton species. Nature Climate Change 3: 298-302.

Sunday, J.M., Bates, A.E. and Dulvy, N.K. 2012. Thermal tolerance and the global redistribution of animals. Nature Climate Change 2: 686-690.

Posted 3 November 2014