When Global Warming Bleaches Coral, Coral Disease Increases

MIAMI, Oct. 6 (UPI) — A U.S. study has found coral bleaching increases the chances of coral disease, which in turn, can exacerbate coral bleaching.

Coral bleaching occurs when colorful algae living inside each coral polyp die or leave the polyps due to global warming. Scientists say they’ve discovered bleaching can make corals more susceptible to disease and, in turn, coral disease can exacerbate the negative effects of bleaching. The study also shows that when disease and bleaching occur together, the combination of afflictions causes greater harm to the corals than either does by itself.

“Traditionally, scientists have attributed coral declines after mass bleaching events to the bleaching only,” said Marilyn Brandt, a post-doctoral researcher at the University of Miami and the study’s lead author. “This study shows that the interplay between diseases and bleaching can play a much larger role than we realized.”

The corals rely on the algae to provide nutrients and supplemental oxygen. Without their brightly colored algae, the coral’s skeleton becomes visible through its transparent tissue, making it appear white, or bleached. Although the tissue remains intact and can recover over time, the condition can cause corals to stop growing and reproducing.

The research is reported in the journal Ecology.

Copyright 2009 by United Press International

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