How does rising atmospheric CO2 affect marine organisms?

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Corals Recover from Bleaching and Hurricane Damage in Marine Reserves
Mumby, P.J. and Harborne, A.R. 2010. Marine reserves enhance the recovery of corals on Caribbean reefs. PLoS ONE 5: 10.1371/journal.pone.0008657.

The authors indicate that while the efficacy of no-take marine reserves in promoting biodiversity and fish biomass by reducing local-scale stressors, such as fishing, has been widely documented, there remains a need to determine "whether reserves can also build coral resilience and offset the effects of global climate change that elevate coral mortality and constrain coral calcification."

What was done
To explore this important question, Mumby and Harborne "studied coral population dynamics at 10 sites throughout the Exuma Cays (Bahamas) over a 2.5-year period (2004-2007) in order to contrast the trajectories of coral populations both inside and outside reserves [that were] severely disturbed by the 1998 coral bleaching event, and later by hurricane Frances in the summer of 2004." This approach was taken based on the oft-observed fact that "protecting large herbivorous fishes from fishing can generate a trophic cascade that reduces the cover of macroalgae," which are major competitors of corals.

What was learned
The two researchers determined that "the proportional increase in coral cover after 2.5 years was fairly high at reserve sites (mean of 19% per site) and significantly greater than that in non-reserve sites which, on average, exhibited no net recovery [italics added]." This differential response was attributed by them to the reduced density of competing macroalgae in the marine reserves that were "depleted by more abundant communities of grazers that benefit[ed] from reduced fishing pressure."

What it means
Mumby and Harborne's findings suggest that marine reserves can indeed "build coral resilience and offset the effects of global climate change." And they also suggest that were it not for the site-specific deleterious effects of humanity on reef environments, this would likely be the case nearly everywhere, which in turn suggests that the local environmental impacts of man are what are harming earth's corals, and not the more speculative global impacts that the world's climate alarmists typically blame on anthropogenic CO2 emissions.

Reviewed 31 March 2010