How does rising atmospheric CO2 affect marine organisms?

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Coral Reefs of Tanzania
McClanahan, T.R., Muthiga, N.A., Maina, J., Kamukuru, A.T. and Yahya, S.A.S. 2009. Changes in northern Tanzania coral reefs during a period of increased fisheries management and climatic disturbance. Aquatic Conservation: Marine and Freshwater Ecosystems 19: 758-771.

The authors note that many people are so convinced about the postulated negative impact of global warming on earth's coral reefs that they automatically assume that "climate overrides and undermines local resource use and management," and that there is thus a "need for management of the atmosphere at the global scale [italics added]."

What was done
In a study designed to evaluate this view of the matter, McClanahan et al. conducted surveys of coral reefs in northern Tanzania "in 2004/5 with the aim of comparing them over an ~8-year period during a time of increased efforts at fisheries management and the 1998 El Niņo Southern Oscillation (ENSO) and Indian Ocean Dipole coral mortality event that caused 45% mortality in northern Tanzania and much of the Indian Ocean."

What was learned
The Kenyan, Swedish, Tanzanian and US researchers report that their repeated surveys "indicate general stability of these reefs over time," and they state that "in the context of the high bleaching and mortality of western Indian Ocean reefs after 1998 (Goreau et al., 2000; McClanahan et al., 2007), the general stability and improvement of these reefs six to seven years after the largest ENSO in recent history (McPhaden, 1999) indicates reefs with considerable resilience to climate change."

What it means
Due to the fact that "all reefs exhibited some resilience and ecological stability and even improvements during this time of climate and management change," as they describe it, McClanahan et al. concluded that this observation "creates considerably more optimism for poor countries, such as Tanzania, to effectively manage their reefs in an environment of climate change." Consequently, they say that "Tanzanian and possibly many other reefs that exhibit similar environmental conditions have the ability to recover from large-scale climatic and human disturbances."

We agree; and we would also add, therefore, that all countries need to implement local measures to protect their coral reefs, and not waste precious time thinking that they -- or even all nations acting in concert -- will ever be able to dictate the course of earth's climate over any foreseeable future timeframe. In addition, as we have repeatedly posited on our website, local environmental protection measures will almost surely enable earth's corals to better withstand the negative consequences of whatever global environmental pressures they may encounter in the future.

Goreau, T., McClanahan, T., Hayes, R. and Strong, A. 2000. Conservation of coral reefs after the 1998 global bleaching event. Conservation Biology 14: 5-15.

McClanahan, T.R., Ateweberhan, M., Sebastian, C.R., Graham, N.A.J., Wilson, S.K., Bruggemann, H., and Guillaume, M. 2007. Western Indian Ocean coral communities, bleaching responses, and susceptibility to extinction. Marine Ecology Progress Series 337: 1-13.

McPhaden, M.J. 1999. Genesis and evolution of the 1997-98 El Niņo. Science 283: 950-954.

Reviewed 25 February 2010