How does rising atmospheric CO2 affect marine organisms?

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Coral Bleaching and Multiple Symbionts
Rowan, R., Knowlton, N., Baker, A. and Jara, J.  1997.  Landscape ecology of algal symbionts creates variation in episodes of coral bleaching.  Nature 388: 265-269.

What was done
The authors examined the relationship between coral symbiont type and the relative amount of damage experienced during a natural episode of coral bleaching.

What was learned
It was found that the dominant Caribbean corals act as hosts to dynamic multi-species communities of symbionts, and that "patterns of bleaching could be explained by the preferential elimination of a symbiont associated with low irradiance from the brightest parts of its distribution..."

What it means
This study highlights the link between solar irradiance and coral bleaching.  It also demonstrates that a single coral can play host to a number of different symbionts having different sensitivities to different environmental stresses.  Consequently, in response to the oft-repeated claim that the ocean's coral reefs will experience an increase in bleaching events induced by increasing temperatures, the authors of this study suggest that "coral communities may adjust to climate change by recombining their existing host and symbiont genetic diversities," thereby reducing the amount of damage that might otherwise be expected from temperature-induced coral bleaching.

Reviewed 1 May 1999