How does rising atmospheric CO2 affect marine organisms?

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The Double Whammy of Global Warming and Ocean Acidification

Paper Reviewed
Chua, C.M., Leggat, W., Moya, A. and Baird, A.H. 2013. Temperature affects the early life history stages of corals more than near future ocean acidification. Marine Ecology Progress Series 475: 85-92.

In a study published in the journal Marine Ecology Progress Series, Chua et al. (2013) write that "climate change is projected to increase ocean temperatures by at least 2°C, and levels of pH by ~0.2 units (ocean acidification, OA) by the end of this century." And they say that "while the effects of these stressors on marine organisms have been relatively well explored in isolation, possible interactions between temperature and OA have yet to be thoroughly investigated." And so it was that they went on to test "whether temperature might act in combination with OA to produce a measurable ecological effect on fertilization, development, larval survivorship or metamorphosis of two broadcast spawning species, Acropora millepora and A. tenuis, from the Great Barrier Reef.

More specifically, the four researchers studied the effects of four different treatments: control, high temperature (+2°C), high partial pressure of CO2 (pCO2, 700 µatm), and a combination of both high temperature and high pCO2, corresponding to the current levels of these parameters and the values projected for them by the end of this century in the IPCC's A2 scenario. And what did they thereby learn?

Chua et al. say they "found no consistent effect of elevated pCO2 on fertilization, development, survivorship or metamorphosis, neither alone nor in combination with temperature." As for warming, they also say that it "had no consistent effect on fertilization, survivorship or metamorphosis." However, they observed that the two degrees of warming actually increased rates of development. And that is good news concerning the future of these organisms!

Posted 19 November 2014