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Coral Calcification in the Face of Large Temperature Variations

Paper Reviewed
Dandan, S.S., Falter, J.L., Lowe, R.J. and McCulloch, M.T. 2015. Resilience of coral calcification to extreme temperature variations in the Kimberley region, northwest Australia. Coral Reefs 34: 1151-1163.

Dandan et al. (2015) introduce their work by writing that "key factors influencing the thermal tolerance of corals are the range and variability in water temperatures to which they are exposed, acting in synergy with specific changes in coral genotype and phenotype, such as the increased production of heat shock proteins and superoxide scavenging, as well as hosting symbionts with more thermally tolerant genotypes," citing Baker et al. (2004), Howells et al. (2011), Stat and Gates (2011) and Palumbi et al. (2014), adding that "such environmentally dependent resilience is particularly evident in the persistent growth and survival of reef-building coral in extreme environments where temperatures frequently exceed more than 30°C," citing Smith et al. (2007), Oliver and Palumbi (2011) and Riegl et al. (2011).

In further exploring this subject, the four Australian scientists measured seasonal changes in coral calcification rates within intertidal and subtidal zones of Cygnet Bay in the Kimberley region of northwest Australia, where they say that "tidal range can reach nearly 8 meters and the temperature of nearshore waters ranges seasonally by 9°C from a minimum monthly mean of 22°C to a maximum of over 31°C during spring low tides." And what did they thereby learn?

Dandan et al. report "there are scleractinian coral species living in high and variable temperature environments which can calcify at rates that are comparable to, or faster than, similar species growing in lower and less variable temperature environments." And they add that "differences in the growth rates of the same species of coral across different habitats within Cygnet Bay are likely to depend on the a priori 'frontloading' of genes involved in heat resistance within the coral host, and/or the ability for corals to adjust their physiology in accordance with short-term changes (weeks) in environmental conditions," as had earlier been found to be the case by Barshis et al. (2013) and Palumbi et al. (2014).

Consequently, it is no surprise that the Australian researchers report that "to the best of our knowledge, there still have been no reports of regional-scale mass bleaching in the Kimberley," suggesting that "the Kimberley region provides an excellent natural laboratory in which to study the ability of scleractinian coral to grow and survive in high and variable temperature environments." And why is that? Because corals actually do it there!

References
Baker, A.C. Starger, C.J., McClanahan, T.R. and Glynn, P.W. 2004. Corals' adaptive response to climate change. Nature 430: 741.

Barshis, D.J., Ladner, J.T., Oliver, T.A., Seneca, F.O., Traylor-Knowles, N. and Palumbi, S.R. 2013. Genomic basis for coral resilience to climate change. Proceedings of the National Academy of Science USA 110: 1387-1392.

Howells, E.J., Beltran, V.H., Larsen, N.W., Bay, L.K., Willis, B.L. and van Oppen, M.J.H. 2011. Coral thermal tolerance shaped by local adaptation of photosymbionts. Nature Climate Change 2: 116-120.

Oliver, T. and Palumbi, S. 2011. Do fluctuating temperature environments elevate coral thermal tolerance? Coral Reefs 30: 429-440.

Palumbi, S.R., Barshis, D.J., Traylor-Knowles, N. and Bay, R.A. 2014. Mechanisms of reef coral resistance to future climate change. Science 344: 895-898.

Riegl, B.M., Purkis, S.J., Al-Cibahy, A.S., Abdel-Moati, M.A. and Hoegh-Guldberg, O. 2011. Present limits to heat-adaptability in corals and population-level responses to climate extremes. PLoS One 6: e24802.

Smith, L.W., Barshis, D. and Birkeland, C. 2007. Phenotypic plasticity for skeletal growth, density and calcification of Porites lobata in response to habitat type. Coral Reefs 26: 559-567.

Stat, M. and Gates, R.D. 2011. Clade D Symbiodinium in scleractinian corals: a nugget of hope, a selfish opportunist, an ominous sign, or all of the above? Journal of Marine Biology 2011: 730715.

Posted 7 April 2016