How does rising atmospheric CO2 affect marine organisms?

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Microhabitats Enable Animals to Beat the Heat of Global Warming
Scheffers, B.R., Edwards, D.P., Diesmos, A., Williams, S.E. and Evans, T.A. 2014. Microhabitats reduce animal's exposure to climate extremes. Global Change Biology 20: 495-503.

The authors note that extreme weather events, such as unusually hot temperatures, can cause death by exceeding an animal's physiological limits and thereby lead to a decrease in its local population, depending on whether or not the susceptible species can find close-at-hand refuges that might mitigate the extreme consequences of the extreme heat.

What was done
In exploring this possibility, Scheffers et al. acquired temperature data from four microhabitats (soil, tree holes, epiphytes, and vegetation) stretching from the ground to the canopies of primary rainforests in the Philippines, where they write that "ambient temperatures were monitored from outside of each microhabitat and from the upper forest canopy," while noting that they also "measured the critical thermal maxima (CTmax) of frog and lizard species, which are thermally sensitive and inhabit the microhabitats."

What was learned
The five researchers - hailing from Australia, the Philippines, Singapore and the UK - report that the microhabitats they studied "reduced mean temperature by 1-2°C and reduced the duration of extreme temperature exposure by 14-31 times." They also say that "microhabitat temperatures were below the CTmax of inhabitant frogs and lizards, whereas macro-habitats consistently contained lethal temperatures." On average, they additionally note that microhabitat temperatures increased by 0.11-0.66°C for every 1°C increase in macro-habitat temperature." And last of all, they say that "assuming uniform increases of 6°C, microhabitats decreased the vulnerability of communities by up to 32-fold, whereas under non-uniform increases of 0.66 to 3.96°C, microhabitats decreased the vulnerability of communities by up to 108-fold."

What it means
In concluding their paper, Scheffers et al. write that their data suggest that "consideration of microhabitats provides a more realistic assessment of exposure within rainforests, possibly reducing exposure to extreme events by an order of 22," and that "inclusion of microhabitat buffering within models is therefore fundamental to making accurate assessments of vulnerability under future conditions."

Reviewed 2 April 2014