How does rising atmospheric CO2 affect marine organisms?

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Developmental Thermal Acclimation in a Species of Damselfish
Grenchik, M.K., Donelson, J.M. and Munday, P.L. 2013. Evidence for developmental thermal acclimation in the damsel fish, Pomacentrus moluccensis. Coral Reefs 32: 85-90.

The authors write that "tropical ectotherms are predicted to be especially sensitive to global warming because they may possess a narrow thermal tolerance range as a result of having evolved in a relatively stable thermal environment." And they say that having a narrow thermal tolerance range would mean that "tropical species tend to live close to their thermal optimum," so that "even relatively small increases in temperature could lead to declines in individual performance," because "as water temperature increases, so does the cost of maintaining basic cell function (resting metabolic rate, RMR; Bret, 1971)."

What was done
To provide a quick check on this line of reasoning, Grenchik et al. reared newly-settled juveniles of the tropical damselfish Pomacentrus moluccensis for a period of four months in four different temperature treatments, which consisted of the current-day summer average (28.5°C) and up to 3°C above the average (29.5, 30.5 and 31.5°C).

What was learned
The three Australian researchers discovered that the RMRs of fish reared at 29.5 and 31.5°C were "significantly higher than the control group reared at 28.5°C," and they indicate that "fish that developed in 30.5 and 31.5°C exhibited an enhanced ability to deal with acute temperature increases."

What it means
In the words of Grenchik et al., "this study shows that there is capacity for thermal acclimation during development, with individuals reared from an early age at some temperatures able to modify their physiology to maintain RMRs at near present-day levels," with the result that this developmental thermal acclimation "may assist coral reef fish to cope with increases in water temperature without a substantial loss to performance."

Bret, J.R. 1971. Energetic responses of salmon to temperature. A study in some thermal relations in the physiological and freshwater ecology of sockeye salmon (Oncohynchus nerka). American Zoologist 11: 99-113.

Reviewed 14 August 2013