How does rising atmospheric CO2 affect marine organisms?

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Tropical Fish May be Well Prepared to Cope with Global Warming
Donelson, J.M., Munday, P.L., McCormick, M.I. and Pitcher, C.R. 2012. Rapid transgenerational acclimation of a tropical reef fish to climate change. Nature Climate Change 2: 30-32.

The authors write that "ocean temperatures are expected to become adverse for many marine species within the next 50-100 years because of global warming," and they say that "tropical species are expected to have less capacity for thermal acclimation than temperate species because they have evolved in a more stable thermal environment." But is this really true? Speculating that it may not be, Donelson et al. conceived and conducted an experiment to find out for themselves.

What was done
The four researchers, as they describe it, "reared siblings from eight wild parental lineages of the tropical damselfish Acanthochromis polyacanthus for two generations in present-day (+0.0°C) and predicted future increased water temperatures (+1.5 and +3.0°C) to test their capacity for metabolic acclimation to ocean warming."

What was learned
The Australian scientists report that acute exposure to elevated temperatures of +1.5 and +3.0°C, which have been predicted to occur this century, caused a 15% and 30% respective decrease in the maximum ability of the fish to perform aerobic activities such as swimming or foraging, which is known as aerobic scope. However, they found that complete compensation "in aerobic scope occurred when both parents and offspring were reared throughout their lives at elevated temperature." And they add that "the ability to acclimate and maintain aerobic capacity would also be expected to maintain performance in characteristics such as growth and swimming ability at elevated temperatures."

What it means
In discussing their remarkable findings, Donelson et al. say that "such acclimation could reduce the impact of warming temperatures and allow populations to persist across their current range." And they conclude their paper by stating that "the discovery that advantageous offspring phenotypes are produced within two generations could indicate that some tropical marine species are more capable of coping with global warming than has been suggested and illustrates a potential limitation of short-term experiments in predicting the long-term impacts of climate change."

Reviewed 11 July 2012