El Niño: Scientists Brace for More Coral Bleaching
By Chris Baskind in Environment
The start of another El Niño event may be welcome news to coastal areas vulnerable to Atlantic basin hurricanes. But it has scientists worried about fragile coral ecosystems.
NOAA’s July Oceans Report confirmed what most climatologists expected: that a new El Niño event is underway, and will likely build through the summer months. El Niño is a weather pattern resulting in the rise of surface temperatures in the Eastern Pacific Ocean, but its effects are felt worldwide. One of El Niño’s most damaging consequences is coral bleaching.
When ancient reefs die
Partially bleached coral
Coral bleaching is the sudden expulsion of tiny, single-cell algae by living coral. This happens under stressful conditions, such as when reef water becomes too warm. It’s algae which gives coral its dark color, so bleached sections appear white. The coral also depends on algae for energy and assistance with calcification.
If the stress ends quickly, new colonies of algae may be able to reestablish themselves in time to save the host coral. If that’s not the case, the coral dies. This is disastrous for a reef, which might experience less than one inch of growth per year.
During the intense El Niño of 1998, up to 16 percent of the world’s reef systems was destroyed by above average sea temperatures.
Most at risk: the Caribbean
The outlook is grim for reefs in the Caribbean and Lesser Antilles, according to new estimates from NOAA’s Coral Reef Watch Program. Scientists expect the current El Niño to persist through through October, threatening a repeat of severe coral bleaching that occurred four years ago. The 2005 El Niño stands as the worst on record, when 90 percent of Eastern Caribbean reefs suffered bleaching. About half the bleached coral died.
Image credit: NOAA
So far, NOAA’s estimates are proving accurate. Measurements released last week by the National Climatic Data Center show that June sea surface temperatures were the warmest ever measured, surpassing even those from 2005. Observation records go back to 1880.
While nothing can be done to lower short-term sea temperatures, Reef Watch officials hope raising the alarm will allow local marine managers to take preventative action limiting other sources of coral stress, such as scuba diving, fishing, and boating. Cruise ships have been blamed for coral damage — thanks to collision, anchor dragging, pollution discharge, and stirring of sediment.
The Cayman Islands was among the first nations to ban cruise liners near sensitive reef areas. With 2009 shaping up as a destructive season for coral, expect to see similar measures taken to protect reef systems across the Caribbean.
Photo credits: Healthy coral (top) by Flickr user moonjazz / CC BY-SA 2.0. Bleached coral image (inset) by Flick user cybersam / CC BY 2.0
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