Heat-tolerant coral reefs may survive global warming

Washington, May 21 (ANI): Stanford University scientists have found evidence that some coral reefs are adapting to the climate change and may actually survive global warming.

"Corals are certainly threatened by environmental change, but this research has really sparked the notion that corals may be tougher than we thought," said Stephen Palumbi, a professor of biology and a senior fellow at Stanford's Woods Institute for the Environment.

Palumbi and his Stanford colleagues began studying the resiliency of coral reefs in the Pacific Ocean in 2006 with the support of a Woods Institute Environmental Venture Project grant.

"The most exciting thing was discovering live, healthy corals on reefs already as hot as the ocean is likely to get 100 years from now," said Palumbi.

Coral reefs form the basis for thriving, healthy ecosystems throughout the tropics.

They provide homes and nourishment for thousands of species, including massive schools of fish, which in turn feed millions of people across the globe.

Corals rely on partnerships with tiny, single-celled algae called zooxanthellae. The corals provide the algae a home, and, in turn, the algae provide nourishment, forming a symbiotic relationship.

But when rising temperatures stress the algae, they stop producing food, and the corals spit them out.

Without their algae symbionts, the reefs die and turn stark white, an event referred to as "coral bleaching."

During particularly warm years, bleaching has accounted for the deaths of large numbers of corals.

In recent years, scientists discovered that some corals resist bleaching by hosting types of algae that can handle the heat, while others swap out the heat-stressed algae for tougher, heat-resistant strains.

Palumbi's team set out to investigate how widely dispersed these heat-tolerant coral reefs are across the globe and to learn more about the biological processes that allow them to adapt to higher temperatures.

In 2006, Palumbi and graduate student Tom Oliver traveled to Ofu Island in American Samoa. Ofu, a tropical coral reef marine reserve, has remained healthy despite gradually warming waters.

The island offered the perfect laboratory setting, with numerous corals hosting the most common heat-sensitive and heat-resistant algae symbionts.

In cooler lagoons, Oliver found only a handful of corals that host heat-resistant algae exclusively.

But, in hotter pools, he observed a direct increase in the proportion of heat-resistant symbionts, suggesting that some corals had swapped out the heat-sensitive algae for more robust types.

According to Oliver, "These findings show that, given enough time, many corals can match hotter environments by hosting heat-resistant symbionts." (ANI)