ANTANANARIVO — A marine expedition into
previously unexplored Indian Ocean waters has found that corals off Madagascar
have resisted so-called "bleaching" associated with global warming, possibly
because of steep drop-offs nearby.
The findings, presented at a conservation conference in the Malagasy capital, could help policy makers decide which areas to protect from illegal fishing, mining or pollution.
The survey was unveiled the day after a global study showed that less than 2 percent of the world's tropical coral reefs are properly protected.
"The expedition found healthy coral reefs that have avoided bleaching attributed to climate change found in other Indian Ocean reefs. The researchers believe cool water currents from adjacent deep ocean areas offset the warming effects of climate change," Conservation International (CI), which organised the survey, said in a statement.
Scientists say global warming linked to greenhouse gas emissions is taking a toll on coral reefs off east Africa. The reefs will likely be killed off in a few decades if sea surface temperatures continue to rise.
Some studies have suggested there was a 70 to 75 percent mortality rate from El Nino-like conditions in shallow water reefs off East Africa in 1997-98.
Models have suggested that the events of 1998 could be repeated on a regular basis in 20 to 50 years' time because of rising sea surface temperatures.
Bleaching refers to the whitening of corals from a loss of pigment. This is a signal of stress which can be triggered by sedimentation, pollution, or rising temperatures, among other factors still being studied by scientists.
But the corals off northeast Madagascar have displayed a resiliency to the phenomenon, possibly because of the cooler currents from neighbouring offshore depths.
"This is important to know because it can allow the government to prioritise the areas it needs to protect," said Sheila McKenna, director of marine biodiversity for CI's Center for Applied Biodiversity Science.
Madagascar's government has committed itself to tripling its network of protected areas to 6 million hectares (14.83 million acres), including 1 million hectares of marine protected areas.
The survey, which involved 27 scuba dives, also found the area to be unexpectedly rich in biodiversity, with around 420 species of fish sighted.
It recorded one fish species believed new to science and 17 others noted for the first time in Madagascar waters.
Reefs are essential to the health of marine ecosystems because they are key spawning grounds and protect coasts from erosion. They also draw scuba-diving tourists.