Sewage casts pox on reefs
Human gut bacterium kills Caribbean
corals.
18 June 2002
JOHN WHITFIELD
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| 90% of Caribbean Elkhorn
coral has died in the past decade. |
| © Uni. of Georgia |
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Human sewage is behind a devastating coral disease, say US
researchers. The finding supports calls to tighten water-quality
regulations in the Caribbean.
Elkhorn coral (Acropora palmata) was once the
commonest in the Caribbean. Over the past decade more than 90%
has died. In 1999, the species was proposed for inclusion on the
US endangered species act.
Central to the coral's decline has been the disease white
pox. This can kill as much as 10 square centimetres of coral per
day, but its cause was unknown. "The tissue appears to melt away
from the skeleton," says marine ecologist James Porter of the
University of Georgia, Athens.
Porter's team grew microbes found in diseased coral from the
Florida Keys, Bahamas, US Virgin Islands and Caribbean Mexico
and infected coral in the laboratory with them.
One of the bacteria from pox-ridden coral, Serratia
marcescens, gave healthy coral white pox. S. marcescens
is in all human faeces, and sometimes causes disease in humans
and fish. This is the first time a gut bacterium has been found
to harm a marine invertebrate.
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| Corals with white pox
contain a bacterium found in human faeces. |
| © Uni. of Georgia |
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The new evidence suggests that sewage treatment should be
improved, says coral researcher John Bythell of the University
of Newcastle-upon-Tyne. "I've no doubt that Serratia
marcescens is one possible cause of white pox," he says.
There could be others, he cautions.
The worldwide decline in coral populations is often blamed on
climate change. Porter says his work shows that the local
environment is also critical. But, he warns, global warming may
yet play a part, by improving conditions for the bacterium.
Illegal cesspits
Elkhorn coral is "the giant redwood of the sea," says Porter.
Its large fronds "provide the three-dimensional structure in
which other plants and animals live".
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| Four years' worth of white
pox damage. |
| © Uni. of Georgia |
|
|
Its decline has coincided with the rise in Caribbean tourism.
Each year 4 million visitors augment the 90,000 inhabitants of
Florida Keys - its reefs are the biggest diving destination in
the world.
"Thousands of illegal cesspits still exist in this county,"
says DeeVon Quirolo, executive director of Reef Relief, a
conservation group based in Key West, Florida. "The problem has
been denial as to whether there is a problem." The bacteria-pox
link should help policymakers clean up the water reaching the
sea, she believes.
Sewage regulations introduced in the Florida Keys National
Marine Sanctuary last year have already resulted in new coral
growth on the reef, says Quirolo: "We're on the road to
recovery". |
