Coral bleaching a recurrent threat to reef
This week is being observed as Coastal Awareness Week and the Coastal Zone Management Authority today held a symposium to discuss critical issues affecting Belize’s marine resources. Among those resources is our Barrier Reef. In 1995 News 5’s Stewart Krohn ventured out to Carrie Bow caye where he documented a phenomenon known as coral bleaching. Today, as then, it is a problem that we may have to learn to live with.
Stewart Krohn, Reporting
With the hemisphere’s longest Barrier Reef, hundreds of offshore islands and three pristine atolls, Belize has earned a reputation as one of the world’s premier destinations for divers. From shallow aquarium-like gardens to immense drop-offs, the underwater world here is a vibrant explosion of colourful coral.
At least that’s the way it’s supposed to be. In the last few months, however, this incredible panorama of marine life has gone from Technicolor to black and white.
It looks like a pine forest that has been dusted by overnight snow flurries. But in fact, it’s a phenomenon known as coral bleaching. First detected in the early eighties off the Florida Keys and Panama, by the end of the decade widespread outbreaks had been recorded in Jamaica and the Virgin Islands in the Caribbean, as well as Australia and other locations the pacific. Up to this year, Belize and its neighbours had been spared, but by late August reports of bleaching were coming in from Texas, Mexico’s Yucatan coast and the Cayman Islands in addition to Belize.
The cause of coral bleaching appears to be related to a dramatic rise in water temperature. Melanie McField, a researcher with Belize’s Coastal Zone Management Project, has been monitoring the situation for several months.
Melanie McField, Marine Biologist
“Coral bleaching is normally attributed to elevated temperatures. Over the summer months we had a lot of calm weather conditions and hot sea and air temperatures.”
Scientists believe that the change in temperature disturbs the balance between the tiny coral polyps and the colourful algae, which inhabit them.
Melanie McField
“There is two theories as to actually why the coral would bleach. One theory states that the animal, the coral polyp itself, slows down its bodily functions, then the algae that lives inside the coral, then isn’t getting all the nutrients it needs and the algae itself takes off and leaves, so the algae will be abandoning the coral. The other theory is that the algae becomes stressed due to the elevated temperatures or the combination of factors that cause the bleaching, then it produces a toxic form of oxygen and then the coral expels the algae because of its toxicity. But either way, what’s happening is the algae is leaving the coral.”
Although it’s most common in relatively shallow areas, the bleaching off Belize is evident as deep as a hundred and twenty feet. It primarily affects the common mountain star coral, but can also be found on various lettuce type corals and certain species of brain coral.
Tony Rath, a marine biologist and photographer, has been diving for years of the Smithsonian Institution’s research station at Carrie Bow caye.
Tony Rath, Biologist/Photographer
“I’ve been diving in these waters for sixteen years and never have I seen coral bleaching to the extent that I see it now. As recently as two weeks ago I was diving in the same location and the bleaching wasn’t nearly as bad as it was today. I would estimate possibly between fifty and seventy percent of the corals are showing some type of bleaching.”
The evidence suggests that in many cases the bleaching process is reversible, that for a time, the coral can survive without their algae and then regain their fated glory.
Melanie McField
“We have reports from other locations where they may live for six months, they may recover. What will probably happen, and we’re already seeing some recovery on the reef from corals that we tagged six weeks ago. Some have recovered, some have partially died and some look the same.”
But coral bleaching or no, Belize’s diving remains fantastic. Stewart Krohn for News 5.
According to McField, following the 1995 bleaching there was an even worse outbreak in 1998. That, coupled with the effects of Hurricane Mitch, resulted in a fifty percent mortality rate in sampled coral colonies. Since that time there has not been another major bleaching event, but scientists have been doing research to see why some areas remained healthy while others succumbed. McField says that since we cannot control coral bleaching, it means that we must work that much harder to minimise the impacts that we can control, like pollution and excessive human intrusion on the reef.
