London: One of the worst bleaching events on record occurred in 2005, thanks to the unusually warm waters in the tropical Atlantic Ocean and Caribbean Sea, but a new study has revealed that 2010 is shaping up to be even worse.
Mark Eakin and his colleagues at US National Oceanic and Atmospheric Administration`s Coral Reef Watch found that more than 80percent of the corals surveyed in the Caribbean were bleached, and at many sites more than 40 percent died.
Corals at Flower Garden Banks National Marine Sanctuary in the Gulf of Mexico also showed signs of bleaching for the first time. They also saw the first mass bleaching of elkhorn coral (Acropora palmata) in the Virgin Islands National Park.
According to Eakin, the only thing that could cause mass bleaching on this geographical scale is high temperatures maintained over a period of months.
"There is some evidence that local factors and other climate-scale factors, such as ocean acidification, sea-level rise and changes in storm intensity, may influence bleaching sensitivity," Nature quoted Eakin as saying.
"But temperature is the big driver."
And because the bleaching is happening faster than the reefs can recover, there is a continuing decline.
"We``re looking at an event of the same magnitude, with temperatures on a par with what we saw in 2005. As far as corals are concerned, 2010 is, in places, as bad as or worse than 2005," Eakin said.
"We need a better understanding of the relationship between temperature and nutrients, how those processes work and how we can actually reduce impacts. But the major challenge is figuring out how to deal with atmospheric and ocean CO2 levels."
If sea temperatures cannot be brought under control by altering atmospheric CO2 concentrations or temperatures, researchers may have to adopt drastic measures – either shading corals with cloth or pumping cool water from the depths over shallow reefs for short periods when temperatures are predicted to be particularly high, said Paul Sammarco at the Louisiana Universities Marine Consortium in Chauvin.
"This would be dicey and difficult to control, but it may be worth investigating."