U.S. Water News Online
WASHINGTON -- The drought in Africa may be partly to blame
for a decline in the coral in the Caribbean Sea, according to a team
of researchers who found coral-damaging fungi in dust blown across
``Coincidental with the decline of Caribbean coral reefs over the
past 25 years, there has been a sharp increase in the transport of
African dust to the western Atlantic,'' reported the team led by
Eugene A. Shinn of the U.S. Geological Survey Center for Coastal
With the long-term drought in Africa, combined with overgrazing in
many areas, the amount of dust carried across the oceans has been
increasing and is now estimated at several hundred million tons
And the threat may not be limited to corals, Shinn said in a
``We have moved into the realm of public health because the dust
is bringing lots of bacteria,'' commented Shinn, who said his
research team has now added a microbiologist to study what types of
microorganisms might be carried on the dust.
In 1989 some one-inch grasshoppers from Africa made it to the
windward islands in a dust storm. ``If they can make it, think of all
the other things that can make it,'' he said.
``Dust often reduces visibility in the Virgin Islands, sometimes
causes temporary closing of airports, and is easily verified as
African in origin by tracking dust clouds across the Atlantic with
... satellite data,'' the scientists reported.
``Our hypothesis is that some of the decline of the reefs in this
region is linked to the increase in dust transport,'' the team said
in a paper published in Geophysical Research Letters.
Aridity and desertification in northern Africa began increasing in
the mid-1960s, worsened in the 1970s and 1980s and then began to
lessen in the 1990s.
Major episodes of Caribbean coral mortality occurred in 1983 and
1987, which were also the two years of the greatest dust movement,
Shinn pointed out. He said iron and other minerals in the dust
affected the water conditions.
In the mid-1990s an epidemic struck sea fans in the Caribbean and
the cause w as found to be the soil fungus Aspergillus, the team
At the time the presence of Aspergillus was attributed to
increased runoff caused by deforestation on Caribbean islands, but
outbreaks also occurred around isolated islands that had no forests.
Shinn's team tested dust samples collected from the air arriving
at the Virgin Islands and discovered several species of fungi,
``African dust is an efficient substrate for delivering
Aspergillus spores; spores are absent when the air is clear,'' they
Coral damage, including bleaching of corals, has also been
attributed to rising water temperatures and the team agreed that this
is probably also a factor.
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