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Algal species helps corals survive in Earth's hottest reefs

"It gives hope to find that corals have more ways to adjust to stressful environmental conditions," said Jörg Wiedenmann, head of the Coral Reef Laboratory at University of Southampton.

By
Brooks Hays

SOUTHAMPTON, England, Feb. 27 (UPI) -- The warming ocean has researchers worried large swaths of corals could suffer bleaching events, jeopardizing their health and the rich biodiversity that depends on them. But not all corals in warm water reefs are affected equally.

Researchers at the University of Southampton and the New York University Abu Dhabi have identified a special symbiotic algae in the Persian Gulf that protects coral among the warmest reefs in the world. Scientists named the new species Symbiodinium thermophilum.

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Most corals get their color from tiny symbiotic algae that embed themselves in the invertebrates' tissue. The coral provides shelter and nutrients, while the algae secrete a sugar vital to the coral's health. But warming ocean waters often instigate bleaching events, whereby algae leave their hosts en masse. Bleaching events can often prove fatal for corals, as they became more vulnerable to disease, predators and pollution.

The newly identified alga offers its hosts a brownish hue.

In closely analyzing the molecular makeup of the symbiotic algae in the Persian Gulf, researchers confirmed the species' uniqueness -- the only species known to be capable of withstanding such high ocean temperatures.

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"We found pronounced differences that set this heat tolerant species clearly aside," explained Jörg Wiedenmann, a professor of biological oceanography at Southampton and head of its Coral Reef Laboratory. "We named it Symbiodinium thermophilum in reference to its ability to survive unusually high temperatures."

Wiedenmann and his colleagues confirmed that the newly named species protects several coral species throughout the Gulf in a range of temperatures.

"It gives hope to find that corals have more ways to adjust to stressful environmental conditions than we had previously thought," added Wiedenmann. "However, it is not only heat that troubles coral reefs. Pollution and nutrient enrichment, overfishing and coastal development also represent severe threats to their survival. Only if we manage to reduce these different forms of stress will corals be able to benefit from their capacity to adjust to climate change."

The new study was published in the journal Current Opinion in Environmental Sustainability.

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