How does rising atmospheric CO2 affect marine organisms?

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The Resilience of Coral Reefs to Global Stressors
Sandin, S.A., Smith, J.E., DeMartini, E.E., Dinsdale, E.A., Donner, S.D., Friedlander, A.M., Konotchick, T., Malay, M., Maragos, J.E., Obura, D., Pantos, O., Paulay, G., Richie, M., Rohwer, F., Schroeder, R.E., Walsh, S., Jackson, J.B.C., Knowlton, N. and Sala, E. 2010. Baselines and degradation of coral reefs in the northern Line Islands. PLoS ONE 3: 10.1371/journal.pone.0001548.

The authors write that "ecological baselines of the structure and functioning of ecosystems in the absence of human impacts can provide fundamental insights for conservation and restoration," which knowledge is especially important within the context of reef responses to possible future global warming.

What was done
Sandin et al., as they describe it, "surveyed coral reefs on uninhabited atolls in the northern Line Islands to provide a baseline of reef community structure, and on increasingly populated atolls to document changes associated with human activities."

What was learned
On the uninhabited atolls, the nineteen researchers observed fish biomass and the proportion of apex predators "greater than previously described from any coral reef ecosystem," as well as "high cover of reef-building corals and crustose coralline algae, abundant coral recruits, and low levels of coral disease," noting that "uninhabited reefs appear to retain greater capacity to survive or recover from major episodes of coral disease or bleaching," whereas reefs with highly altered food webs "do not." Consequently, they say that the uninhabited atolls of the Line Islands "have remained remarkably intact in comparison to the global norm."

What it means
In light of their striking results, Sandin et al. conclude that "protection from overfishing and pollution appears to increase the resilience of reef ecosystems to the effects of global warming," which is essentially the position espoused by Idso et al. (2000), who concluded fully ten years ago that "increases in coral bleaching that may have occurred in response to periods of elevated water temperature over the past two decades have only occurred because of a long-term weakening of coral resistance to thermal stress caused by the gradual intensification of a multitude of local anthropogenic assaults upon the watery environments in which corals live."

Idso, S.B., Idso, C.D. and Idso, K.E. 2000. CO2, global warming and coral reefs: Prospects for the future. Technology 75S: 71-93.

Reviewed 26 May 2010