Twelve years after the severe global bleaching of 1998, corals are once again showing signs of stress from rising water temperatures.
Experts fear that 2010 maybe another very bad year for the world’s reefs.
Marine experts are sounding the alarm after underwater surveys revealed widespread bleaching of the world’s coral reefs.
Corals have a symbiotic relationship with algae, said Clive Wilkinson of the Reef and Rainforest Research Center in Townsville, on Australia’s north-eastern coast, not far from the Great Barrier Reef, the world’s largest coral reef.
“They take the algae virtually prisoner, so the algae have to produce sugar for the corals,” he explained. With high temperatures and bright sunshine, the algae start creating toxins.
The corals then spit out their energy source. The coral still alive, but starving and susceptible to disease. They have no energy for reproduction and eventually die.
Up to 90 percent of Thailand’s corals are bleaching, experts said, while significant paling is affecting reefs off Indonesia’s island of Sumatra and in the Caribbean.
Scientists blame the rise in water temperature for the bleaching. It does not kill the coral directly, but does leave it vulnerable to disease and unable to reproduce which often leads to its death.
The algae are what lend the coral its eye catching colors. The loss of the algae causes it to take on a bleached appearance.
Wilkinson, who heads the Global Coral Reef Monitoring Network, is alarmed by its findings this year, which he said could be as bad as 1998, when 16 percent of the world’s coral was lost.
This year has so far seen a global water temperature on average of 0.67 degrees Celsius higher than in the middle of the last century, exactly the same average temperature as in 1998.
“In South East Asia, this has led to bleaching that was extremely severe,” said Mark Easkin, director of the coral programme at the US National Oceanic and Atmospheric Administration (NOAA).