[Coral-List] FW: Reef coral in Caribbean is dying off, study finds
mrobbart at pbsj.com
Thu Jul 31 16:39:30 EDT 2003
Thought you might find this interesting.
Martha Lane Robbart
Reef coral in Caribbean is dying off, study finds
80% decline in cover in 30 years is widespread, unexpected, scientists say
By David Kohn
July 18, 2003
Coral reefs across the Caribbean have suffered an 80 percent decline in
cover during the past three decades, a far more devastating loss than
scientists had expected, according to a study released yesterday.
"It's depressing," said marine biologist Isabelle Cote, one of the authors
of the study, which appeared in this week's Science. "We all knew that we
had a bad situation on our hands. But nobody expected it to be this bad."
The researchers gathered information from 65 previous studies of 263 sites
and analyzed it to construct a regional picture.
They discovered a sharp drop in the coral almost everywhere in the
Caribbean, from Florida to South America. Coral covered about 50 percent of
the average reef in the early 1970s but only 10 percent now.
Other researchers were surprised by the findings.
"Everybody sees a bit of the problem in their area. For someone to say the
whole Caribbean is in a downward slide, that's a shock," said Clive
Wilkinson, who runs the Global Coral Reef Monitoring Network. Caribbean
reefs cover almost 10,000 square miles, about 10 percent of the world's reef
He said 10 percent coverage indicates a reef that's not healthy. Reefs
consist of dead coral, which serves as a foundation for living coral, algae
and other organisms. On healthy reefs, living coral covers 60 percent or
more of the surface.
Like their counterparts around the world, Caribbean coral reefs are subject
to a variety of threats, most of which stem from humans.
For example, overfishing in Jamaica has sharply decreased the number of
parrotfish and surgeonfish, which feed on seaweed. In turn, that leaves more
seaweed to compete with coral for space on the reefs. On many Caribbean
reefs, seaweed has largely choked off coral.
Increased water temperatures due to El Nino and global warming have also
killed coral, scientists say. Coral exists in a symbiotic relationship with
microscopic algae, which produce energy for their hosts. But when the water
temperature rises too high for more than a week or so, the algae produce
free radicals that damage the coral.
In response, the coral expels the algae. But without algae, the coral
starves. This is known as "bleaching" because, without the colorful algae,
the coral turns white. In 1998, warm water killed about 10 percent of the
world's coral, the report said.
Over the past 20 years, several diseases have killed Caribbean coral
species. Pollution has taken its toll, too, including agricultural runoff,
mud and silt from cleared forests and raw sewage that can smother coral,
according to Cote, a professor at the University of East Anglia in Britain.
Because of the Caribbean's geography, its coral is particularly sensitive to
"The problem with the Caribbean is it's a big lake," said Wilkinson. "So
everything that comes into there from the Mississippi, from Mexico, Central
America, South America and even as far as the Amazon, all this runoff and
pollution doesn't drain out quickly."
Another problem: Compared with other reef regions, the Caribbean has a large
human population, which catches more fish and produces more pollution.
The disappearance of coral could have wide-ranging implications. Reefs
provide habitat for millions of species, some of which might prove useful to
humans, Cote said.
The anti-AIDS drug AZT, for example, is derived from a Caribbean sponge that
lives on reefs. But there are other more immediate concerns, including drops
in tourism and fish harvests. Healthy reefs also serve as a wave break,
protecting shores from tropical storms.
The current decline is "unprecedented," according to Caribbean coral
researcher Bill Precht, who has studied the region for 25 years in Belize,
Jamaica, Florida and the Bahamas. Precht has done historical research,
drilling cores of ancient reefs going back 3,000 years. "What is going on
with Caribbean reefs, this is the first time this has happened," he said.
The key now is to pinpoint which problems are causing the worst harm, Precht
said: "Humans are clearly the vector. The question is how are we the
Although Wilkinson said extinction was unlikely, some researchers do not
rule out the possibility. Without help, some of the Caribbean's 70 to 100
coral species could easily disappear altogether, said University of Kansas
coral researcher Bob Buddemeier.
"It's grim. The people aren't going to go away. The climate is going to get
worse. A lot of these countries don't have the wherewithal to protect the
reefs. If we're lucky, we can stabilize things where they are now."
Copyright (c) 2003, The Baltimore Sun
Link to the article:
More information about the Coral-List