How does rising atmospheric CO2 affect marine organisms?

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Multiple Symbionts in Corals
Rowan, R. and Knowlton, N.  1995.  Intraspecific diversity and ecological zonation in coral-algal symbiosis.  Proceedings of the National Academy of Science, USA 92: 2850-2853.

What was done
Samples from two dominant Caribbean corals were collected at a range of depths and examined for the number of symbiont algae.

What was learned
It was found that the two Caribbean corals act as hosts to three taxa of symbionts that exhibit zonation with depth.

What it means
Zonation of symbiont type by depth, according to the authors, "strongly supports the theory that hosting different types of zooxanthellae [symbionts] permits corals to acclimate or adapt to different photic habitats."  In addition, their findings "establish empirical precedents for suggestions that intraspecific and intracolony variability in the stress-mediated disruption of coral-algal symbioses [coral "bleaching"] is a manifestation of zooxanthella diversity and that bleaching could promote adaptive changes in coral-zooxanthella association."

Reviewed 1 May 1999