Unusually warm ocean temperatures this year have led to mass devastation of the world's corals, and prospects for their long-term survival are grim, a top government scientist said yesterday.
"Right now, coral reefs around the world are either bleached, dead from bleaching or trying to recover from bleaching," said C. Mark Eakin, who coordinates the National Oceanic and Atmospheric Administration's Coral Reef Watch. "2010 has been a major, major year of coral bleaching in all of the oceans around the world."
Bleaching occurs when corals expel the microscopic algae that normally live inside their hard skeletons, providing them with food and their bright coloration. Changes in ocean salinity, nutrient runoff and other pollution can cause small-scale bleaching, but scientists say the widespread global bleaching this year is a symptom of unusual ocean warming.
A similar global bleaching event in 1998-1999 destroyed 15 percent of the world's coral reefs. 2010 may not be far behind, Eakin said.
"In 2010, we've been seeing the second global-scale series of bleaching events. They're not as severe as what happened in the late '90s, but it's one of those things -- how bad does it have to be?" he said. "These are both big events. They are really severe."
Scientists have observed reefs bleaching this year in Kuwait, the Maldives, Southeast Asia, the Philippines, central Pacific islands and now the Caribbean, where corals also suffered severe bleaching in 2005.
"Places like the Maldives and reefs in Southeast Asia that were just recovering from '98 are now bleached again," Eakin said. "In Thailand this June, it was frightening. It was hard to find corals that were not bleached."
Rising temperatures are the cause
The question now for scientists is whether the world's reefs will be able to recover from this year's bleaching event, and how they will fare as the world warms.
The 1998-1999 bleaching event was driven by a strong El Niño weather pattern, but El Niño wasn't a major factor in the widespread Caribbean bleaching in 2005 or in the development of this year's bleaching event.
"As temperatures are rising, as the baseline is going up, it doesn't take much of a climate event to push these reefs over the edge," Eakin said.
Two Atlantic Ocean coral species -- elkhorn and staghorn -- are listed as "threatened" under the Endangered Species Act, and NOAA is considering whether an additional 82 coral species also warrant some level of protection under the law because of threats from warming water, ocean acidification and pollution.
Ultimately, creating a safe environment for the world's reefs may require efforts to cut the level of carbon dioxide in the atmosphere to just 350 parts per million, well below the current level of 390 parts per million.
"Even once we stop CO2 emissions, we're looking at another century of warming temperatures and another degree Centigrade rise," Eakin said. "This is something that will be hard on corals even if we start acting now."
Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500