How does rising atmospheric CO2 affect marine organisms?

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Rapid Acclimation of a Reef-building Coral to Temperature Stress

Paper Reviewed
Bay, R. A. and Palumbi, S.R. 2015. Rapid acclimation ability mediated by transcriptome changes in reef-building corals. Genome Biology and Evolution 7: 1602-1612.

Introducing their work, Bay and Palumbi (2015) write that "whether [coral] populations persist during anthropogenic climate change will depend partly on the relative rates of increase of thermal tolerance and of environmental temperatures." The degree of thermal tolerance depends, in large measure, on an organism's ability to adapt (evolutionary change) and/or acclimate (physiological change) to temperature stress. In long-lived organisms, acclimation generally produces the more rapid response, and therefore "understanding the rate of acclimation relative to the rate of environmental change," according to Bay and Palumbi, is "crucial." However, the two scientists are quick to note that "fine-scale studies of the acclimation process over short periods of time remain rare."

In an effort to remedy this dearth of information, the pair of Stanford University researchers set out to conduct a laboratory-based experiment to investigate the temperature acclimation of a reef-building coral, Acropora nana. More specifically, colonies of A. nana were subjected to three baseline temperature regimes, ambient (29°C), elevated (31°C) and variable (29-33°C, mimicking the diel tidal fluctuation range), where after 0, 2, 7, and 11 days of treatment, samples were taken and evaluated for their response to acute temperature stress (5 hours of 34°C temperature).

Results indicated that after a mere seven days of exposure to each coral colony's respective baseline temperature regime, A nana specimens subjected to acute temperature stress displayed a "striking increase in heat tolerance," which tolerance was higher in corals acclimated to elevated and variable temperature regimes as opposed to the ambient treatment.

As for the significance of these findings, Bay and Palumbi say they suggest that corals "can track environmental temperatures better than previously believed," and that the observed temperature acclimation may well provide "some protection for this species of coral against slow onset of warming ocean temperatures." They also note that "such rapid change in heat sensitivity runs contrary to coral bleaching models based on fixed thermal tolerance that are currently used to predict coral bleaching and climate change response," citing the works of Liu et al. (2013) and Logan et al. (2013), which suggest predictions of future coral reef demise due to rising ocean temperatures are overstated.

Liu, G., et al. 2013. Coral reef watch 50 km satellite sea surface temperature-based decision support system for coral bleaching management. Silver Spring (MD): NOAA/NESDIS.

Logan, C.A., Dunne, J.P., Eakin, C.M. and Donner, S.D. 2013. Incorporating adaptive responses into future projections of coral bleaching. Glob Change Biology 20: 125-139.

Posted 11 December 2015