A recent survey of coral reefs along Madagascar's southwestern coast discovered that rising sea temperatures made massive damage in coral reefs.

In some areas, 99 % of the coral cover was lost. Even if blighted, these coral reefs may provide the key of recovery for reefs devastated by rising sea temperatures.

The researchers from the conservation groups Blue Ventures and the Wildlife Conservation Society also found some reef patches with corals that seemed to be tolerant to warmer sea temperatures. These coral types could be used to revitalize damaged reefs. "To find these little loci of resistance is extremely rare and is of massive conservation importance," said Alasdair Harris from Blue Ventures.

"As climate change poses an increasing threat to our marine habitats, these resilient areas could hold the key to ensuring the continued existence of coral reefs around the world and the marine species that rely on them for survival," he added.

Warmer waters provoke coral bleaching, when the coral lose their symbiotic algae which provide them with both food (98 % of the coral food is provided by the algae) and color. The brilliant reds, oranges and browns of the corals are due to these tinny plants. Warmer sea temperatures cause the death of the algae and subsequently of the coral, which will look white.

With the global warming, sea temperatures in many tropical areas have been rising over the past 100 years and reef bleaching is now common over the tropics. In 1998, bleaching affected 75 % of coral reefs around the world in 1998. "There has been mass mortality relating to hot sea surface water," Harris said.

The hardy reefs may deliver clues about coral protection from future damage. "This survey shows how important it is to locate and protect areas of resilient corals," said Harris.

The researchers urge the creation of marine protected areas to ensure the long-term survival of the reefs. Land diversity of Madagascar, the world's fourth largest island, is quite well studied, but its marine life is much less known. These coastal waters harbor one of the highest marine diversity in the Indian Ocean.

During the survey made along the reefs off southwestern Madagascar, scientists found more than 500 species of fish, amongst which 20 new for Madagascar. 164 species of reed forming coral were also counted, including 19 new for Madagascar. 4 coral species were untraceable and could be new species.