By PAUL RECER, AP Science Writer
WASHINGTON
(AP) - A one-two-three punch of hurricanes and flooding rains
in North Carolina in 1999 will upset for years the natural balance
of Pamlico Sound, a nursery for crab, shrimp and other sources
of seafood, a study shows.
In just six
weeks in 1999, North Carolina was battered by three hurricanes,
Dennis, Floyd and Irene, and some areas were inundated with rains
so heavy that there were floods not expected to be matched again
in 500 years.
The floods
of fresh water flowed into Pamlico Sound, flushed out the salt
water and caused the fish to swim away, while killing those that
couldn't, researchers report on Tuesday in the Proceedings of
the National Academy of Sciences.
There was
a vast die-off of blue crab, oysters and clams. Bacteria and other
bottom dwelling organisms that form the foundation of the food
chain were devastated.
Nutrients
washed in by the flood caused a bloom of algae, creating areas
of the sound devoid of oxygen. It took a whole year for oxygen
levels to be restored to some waters.
"There
have been great changes in the system and there could be effects
that last for years," said Hans W. Paerl, a University of
North Carolina at Chapel Hill researcher and the first author
of the study. "The effects certainly are not over yet."
Nonetheless,
he said, "the Pamlico system is still very productive,"
with many fish and shrimp returning.
Paerl said
researchers are concerned about what will happen to Pamlico Sound
if, as predicted, more hurricanes come roaring in from the Atlantic
and once more flood the watershed that feeds into the sound.
"We've
been able to dodge a bullet, but if we get increased hurricane
activities over the next two decades, as some predict, we don't
know how much the sound can take," said Paerl.
Researchers
are still studying the effects and believe that some of the key
elements of the food chain still are disrupted.
Larry Crowder,
a marine sciences researcher at Duke University, said that the
floods wiped out a generation of crabs, the one-year-olds that
would have been harvested in 2000.
"They
were no-shows in 2000," said Crowder, a co-author of the
study. "The catch was down to about a third of what is typical.
Even right now, the blue crab numbers are as low as we've ever
seen them."
Crowder said
studies also suggest there is a sharp decline in bottom-feeding
fish, such as spot, croaker and flounder, while other fish, such
as menhaden and bay anchovy, seem unaffected.
"When
the system went from salt water to fresh water for two months,
it killed everything on the bottom," said Crowder.
Catches of
some fin fish have dropped by 50 percent in 2000, while it was
a bumper year for shrimp and for some species that could escape
the fresh water and return to the sound with the salt water.
A shortage
of crab, however, is apt to affect other fish, such as striped
bass, that feed on the crab, said Crowder.
"It will
probably take several years to recover," said Crowder.
Pamlico Sound,
second in size on the East Coast only to Chesapeake Bay, is a
major nursery for crab, oyster, shrimp and many other fish. As
a result, the changes in Pamlico could affect areas far beyond
its waters, the researchers said.
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