Corals may starve as oceans acidify

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Scientists from the University of Queensland have found that ocean acidification, in addition to its adverse effects on the reef-building capabilities of corals, may also cause them to starve.

Alicia Crawley and coauthors investigated the effect of increasing carbon dioxide on the photosynthetic capacity and photoprotection in the coral Acropora formosa; the results of their study are to be published in an upcoming issue of the journal Global Change Biology.

The authors subjected 24 colonies of A. formosa to different elevated levels of carbon dioxide (representing different climate change scenarios for 2100) and carried out respirometry assays to determine the photosynthetic rate of the symbiotic dinoflagellates (Symbiodinium).

The results were compared to those from 12 colonies maintained as a control.

They found that under the business as usual scenario for climate change, the increase in carbon dioxide levels led to a decrease in coral productivity. This decrease is brought about by a 45"50% reduction in the production of a key enzyme (phosphoglycolate phosphatase) that protects the dinoflagellates from harmful solar radiation.

This reduced productivity may lead to more bleaching as the coral expel the zooxanthellae following a prolonged spell of decreased productivity.

For more information, see the paper: Crawley, A, DI Kline, S Dunn, K Anthony and S Dove (2009) The effect of ocean acidification on symbiont photorespiration and productivity in Acropora formosa. Global Change Biology doi: 10.1111/j.1365-2486.2009.01943.x