Newly discovered algae could save world's coral from climate change

A new species of algae discovered in the Persian Gulf may help declining coral populations survive as climate change warms ocean temperatures and threatens reefs with often-fatal bleaching, according to a new report.

Researchers from the University of Southampton and New York University Abu Dhabi identified the algae while studying the world's warmest coral reef habitat, located in Abu Dhabi, United Arab Emirates, to understand how it survived such extreme temperatures.

"Understanding how corals survive under the extreme temperatures in the Gulf will give us important insights into the ability of reef corals to handle the heat stress, which is threatening their survival in the oceans that are warming up in response to climate change," Jörg Wiedenmann, professor of biological oceanography and head of the coral reef laboratory at the University of Southampton, said in a statement.

Reefs are made of many coral species, most of which live in symbiotic relationships with algae, according to researchers. Both species benefit as the algae produces sugars necessary for the diet of the coral, which offers shelter and nutrients vital for algae.

That mutually beneficial relationship is vulnerable to rising ocean temperatures as a result of climate change, according to the report, published in the journal Scientific Reports. Heat stress causes the loss of algae, which often results in coral bleaching. The increasing frequency and duration of such heat stress is a major threat to the reef's survival. Warmer ocean temperatures have already caused fatal coral bleaching.

But the type of algae that grows on Gulf coral, called Symbiodinium, is able to cope with those changes, scientists found. It could survive maximum temperatures of 34 to 36 degrees Celsius (93.2 to 96.8 degrees Fahrenheit) as well as annual temperature fluctuations of up to 20 degrees Celsius, or 68 degrees Fahrenheit.

That, according to researchers, means that at least some coral-algae partnerships would survive conditions predicted to occur in most coral containing waters by the end of the century.

"We monitored the symbiotic partnership over several seasons to ensure that this association was stable through a range of thermal conditions," said Professor John Burt of New York University Abu Dhabi. "We can confirm that this new type of alga is indeed the year-round prevalent symbiont across several dominant coral species from the Abu Dhabi coast of the United Arab Emirates."

Models predict coral reefs will experience annual coral bleaching by 2040, threatening the species with extinction if it is unable to adapt to warmer waters, the report said. Even as little as a 1 degree Celsius increase in average temperatures can be fatal for most coral.

Global temperatures have risen 0.85 C on average since the Industrial Revolution — a change most scientists blame on human activities like the burning of fossil fuels. At current levels of emissions, the world is on track for as much as a 5 degree Celsius rise by 2050.

Scientists tend to agree that capping global temperature rise at 2 degrees Celsius would save the planet from the most severe effects of climate change. But others argue that even a rise of 2 degrees Celsius would trigger positive feedback cycles, which refers to effects from warming that lead to even more warming.

That worries scientists because coral reef die-off, when coupled with melting ice-sheets and the destruction of the Amazon rain forest, could trigger grave global consequences if stressed beyond their limit by rising temperatures.

Given this potential threat, ensuring coral reefs survive is important for the stability of the global climate, the report said.

"It gives hope to find that corals have more ways to adjust to stressful environmental conditions than we had previously thought," said 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."