NEWS YORK TIMES: Mysterious New Diseases Devastate Coral Reefs
Griffis, Roger B
Roger.B.Griffis at noaa.gov
Wed Aug 20 19:12:32 UTC 1997
FYI
_______________________
August 19, 1997
NEWS YORK TIMES: Mysterious New Diseases Devastate Coral Reefs
Mysterious New Diseases Devastate Coral Reefs
By CAROL KAESUK YOON
[T] wo coral researchers were asked to examine the
reefs off the island of Bonaire in January after
divers noticed strange white lesions on the star and
brain corals in waters considered to be among the most
pristine in the Caribbean.
Under water, the researchers, Dr. Thomas J. Goreau and
James Cervino, found something they had never seen
before, huge patches of dead coral, bright white where
the skeleton had been exposed after tissue had died;
the skeleton itself was crumbling away.
"We were quite horrified," said Goreau, who along with
Cervino is with the Global Coral Reef Alliance, a
nonprofit organization for the protection and
management of reefs. "It looks like someone poured acid
over the top of the coral. The skeleton itself is
dissolved. I've been looking at reefs in the Caribbean
probably longer than anyone else alive and I'd never
seen it before. It's attacking at a speed and with a
level of damage that is unprecedented."
The researchers say rapid wasting disease, so named
because it can spread several inches across a coral
head in a single day, is all over the reefs of Bonaire
and since January has been spotted in Mexico, Aruba,
Curacao, Trinidad, Tobago, Grenada and St. John's in
the Virgin Islands, an area spanning 2,000 miles.
But more alarming than the spread of rapid wasting
disease is the fact that it is only one among many
mysterious new diseases that have been discovered
attacking corals around the world. In what they are
describing as an epidemic, researchers say that in the
last few years corals, some centuries old, from the
Florida Keys through the Caribbean to places as distant
as the Philippines, are quickly succumbing to diseases
never before seen.
Unlike the many other stresses on corals with which
scientists and the public have become quite familiar,
including bleaching, sedimentation, pollution and
rising sea temperatures, the rash of new diseases has
taken researchers by surprise.
"We're all stunned at the rapidity with which these new
diseases are occurring," said Dr. James W. Porter, a
marine ecologist at the University of Georgia in Athens
who last year discovered a new disease known as white
pox. "The problems are occurring at all depths, and the
numbers of species affected is increasing as well as
the number of individuals. It's definitely on the
rise."
Dr. Drew Harvell, an ecologist at Cornell University in
Ithaca, N.Y., whose graduate student in the
Philippines, Laurie Raymundo, recently found a disease
in all her study areas that they have been unable to
identify, said: "There seem to be more diseases than
anyone can keep up with. There are a lot of new names
and attempts to correlate symptoms with names and with
causes, but so far, heaven only knows what's going on."
Fewer than a dozen of the new diseases even have names
and those with names are still in the process of being
documented, leaving biologists to rely on word of mouth
to keep the growing number of maladies straight. As a
result, simply recognizing whether a coral is healthy
or sick can be extremely difficult, even for practiced
researchers.
Last month at a meeting of the Association of Marine
Laboratories of the Caribbean held in San Jose, Costa
Rica, Goreau spoke at a special daylong session devoted
to coral diseases, one of the first chances researchers
have had to exchange information on the problem.
"I showed about 50 pictures" of coral diseases, said
Goreau, "but it wasn't nearly enough. Most people are
saying, 'We're seeing all of these but we just didn't
know it before.' " For example, rapid wasting disease,
which exposes a white, crumbling skeleton, is easily
and often mistaken for anchor damage or parrotfish
bites.
Scientists say they have no idea why diseases are
exploding on corals now. Some speculate that multiple
stresses, like bleaching, sedimentation and pollution,
have pushed corals to the breaking point so that they
are now unable to fend off diseases that they have
fought off in the past. With the scant and scattered
information researchers have so far on where the
diseases are, there seems to be little sense to their
spread, with some pristine reefs succumbing to disease
while other much more polluted reefs remain healthy.
"It's a baffling situation," Goreau said. "Most
diseases are new. They don't correlate with each other
or any known environmental stress. In Bonaire, rapid
wasting disease is having a devastating impact, yet the
reefs there are so clean."
Others have suggested that perhaps erosion and the
dumping of sewage and other wastes into the sea has
brought a whole host of new pathogens in contact with
corals and some are taking hold. While the notion that
terrestrial pathogens might begin underwater attacks on
corals might seem far-fetched, researchers say there is
evidence that at least one of the newly emerging
diseases, sea fan disease, is caused by an organism
that invaded from land.
Discovered just four years ago, this disease of soft
corals is now widespread in the Caribbean and has been
shown to be caused by a highly opportunistic fungus
called Aspergillus. Adhering to sediment that has
washed into the sea, the fungi begin to grow when they
encounter a sea fan. Researchers say they are sure it
is a fungus brought from land because it cannot
complete its life cycle in the ocean. "It's a
terrestrial organism that has crossed the land-sea
barrier," Harvell said.
Researchers suspect a fungus is behind rapid wasting
disease and various bacteria are implicated in other
new coral diseases. But for the most part, definite
causes remain unknown.
Scientists say even corals in aquariums, like the
Waikiki Aquarium in Honolulu and the National Aquarium
in Baltimore, are being hit.
In order to make identification of diseases more
straightforward, some researchers are trying to develop
molecular tests for coral diseases. Dr. Harvell and
colleagues are working on a test for sea fan disease,
trying to develop a sort of DNA fingerprint of the
pathogen that would allow researchers who suspect that
a coral has the disease to test DNA from the infected
area and find out definitively if the fungus that
causes sea fan disease is present.
As scientists struggle to identify illnesses, cures for
sick corals appear to be a long way off. Some have
suggested simply applying antibiotics to the reefs.
Scientists warn, however, of the unknown hazards of
dispensing into the seas a drug that can destroy useful
bacteria as easily as harmful bacteria and that may not
do any good if the pathogens that are involved turn out
not to be bacteria at all.
Researchers have had the most luck treating black band
disease by vacuuming off the diseased band of tissue
that gives the illness its name. But the work is
extremely time-consuming, and that type of approach is
practically impossible for the most quickly spreading
and worrisome diseases.
"I couldn't imagine going out and treating a disease
like that," said Dr. Laurie Richardson, an aquatic
microbiologist at Florida International University in
Miami who studies white plague type 2, a disease that
swept through the upper Florida keys in 1995. In just
four months, it spread more than 100 miles, jumping
from one to 17 species of corals.
But while scientists lament having to stand back and
watch these diseases ravage coral populations, they
note that sometimes no treatment can be the best cure.
Once a disease is allowed to rage through an area, any
healthy, resistant individuals left behind can begin to
rebuild a tougher population.
Other inhabitants of reefs are beginning to come down
with diseases as well. Dr. Goreau said sponges,
coralline algae and sea urchins were also succumbing to
new illnesses, further threatening the health of reef
communities.
Coral reef biologists say they are further frustrated
by a lack of money for such quickly unfolding research.
"We've tried getting money from the National Science
Foundation," said Dr. Goreau. "You send a proposal and
wait a year or two for the review. You can't deal with
this kind of emergency science that way."
Researchers are now scrambling to document the extent
of these emerging diseases, the numbers and types of
corals attacked, and the level of virulence of these
pathogens. But with such basic information still
largely unknown, they are left with a mixture of dread
and hope.
Cervino, for one, is soliciting reports of new
outbreaks of coral diseases from observers around the
world. His e-mail address is: cnidariaearthlink.net.
"There are places where there are 200- and 300-year-old
coral colonies being devastated," said Dr. Esther
Peters, senior scientist at Tetra Tech, an
environmental consulting company in Fairfax, Va., "and
there are places where the corals are fine. I'm afraid
it is getting worse, but all is not lost yet."
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