Corals Partner Up With Heat-Resistant Algae

Corals around the world, already threatened by pollution, destructive fishing practices and other problems, are also widely regarded as among the ecosystems likely to be first — and most — threatened with destruction as earth’s climate warms.

But there is reason to hope, researchers are reporting. The scientists, from Penn State University and elsewhere, have produced new evidence that some algae that live in partnership with corals are resilient to higher ocean temperatures. One species, Symbiodinium trenchi, is particularly abundant – “a generalist organism,” the researchers call it, able to live with a variety of coral hosts.

Corals and algae live together in what scientists call a symbiotic relationship. Coral polyps shelter the algae and as the tiny plants photosynthesize they produce sugars the corals rely on for food. When water warms, though, reefs’ brown or green algae partners die, leaving the reefs white. These so-called bleaching events have become more common as ocean waters warm.

The new research focused on corals in the Andaman Sea, in the northeastern Indian Ocean, but other scientists have made similar algae findings in the Caribbean Sea and the Pacific Ocean.

Heat-resistant algae are not enough to save corals, most researchers agree, but their presence may buy time for some reefs. Other researchers have suggested that unusual periods of warm water may allow heat-resilient algae to proliferate, to the long term benefit of corals.

Unfortunately, though, heat-resilient algae do not necessarily occur in corals everywhere. And it is not clear whether importing the algae to threatened reefs would work to save them. “You never know what the effects might be of introducing an organism into an ecosystem in which it is not well established,” Todd LaJeunesse, one of the Penn State researchers said in a statement reporting the new work.

Also, while the algae findings offer a glimmer of hope, there remain plenty of reasons to worry. Perhaps chief among them is the fact that as ocean waters absorb carbon dioxide they become more acidic, threatening the coral skeletons.

source: http://dotearth.blogs.nytimes.com/2010/02/18/corals-partner-up-with-heat-resistant-algae/

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