Washington, Feb 22 (IANS) Researchers have stumbled on a diversity of corals harbouring unusual species of symbiotic algae in the warm waters of the Andaman Sea.

'The existence of so many novel coral symbioses thriving in a place that is too warm for most corals gives us hope that coral reefs and the ecosystems they support may persist -- at least in some places -- in the face of global warming,' said Todd LaJeunesse, who led the study.

Corals are colonies of tiny animals that derive nutrients and energy from golden-brown, photosynthetic algae that live inside the corals' cells.

'This symbiotic relationship is sensitive to changes in the environment,' said LaJeunesse, assistant professor of biology at Penn State University (PSU).

LaJeunesse said the comprehensiveness of his team's survey, which also included analysis of the corals and symbiotic algae living in the cooler western Indian Ocean and Great Barrier Reef area of Australia, is unparalleled by any other study.

'For example, because the algae are photosynthetic, they are very sensitive to changes in light. They are also sensitive to temperature,' he said.

'An increase in sea-surface temperature of just a few degrees Fahrenheit for a period of several months can cause many of the coral-algal symbioses to break down and the algae to be expelled.'

'This process is known as bleaching because it leaves behind the clear animal tissue and the white skeleton underneath. When bleaching is severe, due to either high temperatures or low light availability, corals soon die without their symbiotic partners,' he added.

LaJeunesse said that continued global warming eventually may cause the demise of coral-reef ecosystems, which would have major impacts on the tourism and food-fisheries industries.

His research associate Ove Hoegh-Guldberg, professor at the University of Queensland, Australia, said coral-dominated reefs may become scarce within the next 30 to 50 years, given the increase in the number of bleaching events that have taken place recently.

The team's findings are slated for publication in the February online issue of the Journal of Biogeography.