TABLE OF CONTENTS
FRONT PAGE
NEXT ARTICLE
PREVIOUS ARTICLE
RELATED STORIES
Water testing and a flight over North Carolina's Pamlico Sound -- the
nation's largest lagoonal estuary -- provided new evidence that the
catastrophic flooding and runoff following Hurricane Floyd will damage the
sound and connected waters.
Both commercial and recreational fisheries could be hurt along much of the
southeastern U.S. coast between Virginia and northern Florida, according to a
University marine scientist.
The first direct assessment of potentially adverse marine life conditions
took place Oct. 6. During the survey, researchers observed low oxygen in the
sound and strikingly different colored water.
"The chocolate-colored sediment plume associated with flood discharge from
Floyd has now extended into Pamlico Sound and also is making its way down Core
Sound," said Hans Paerl, Kenan professor of marine sciences.
"We found low oxygen `dead zone' conditions in bottom waters in a region
of the sound under the influence of the sediment plume," Paerl said. "This is
obviously not a good development. In addition, nutrient enrichment associated
with the plume has the potential for triggering fall and early spring
phytoplankton blooms which could further fuel the low-oxygen
conditions."
If the excessive freshwater discharge continues into next spring,
scientists should detect a low-density freshwater "lens" covering denser
saltwater, much like oil floating on vinegar in unshaken salad dressing, he
said.
Resulting isolation of salty bottom water prevents oxygen replenishment
from the atmosphere, leading to development of the oxygen-deficient dead zone.
Algal blooms can exacerbate the condition, because decaying blooms will
ultimately sink to the bottom, further contributing to oxygen depletion. Bottom
water with little or no dissolved oxygen would prove uninhabitable to finfish
and shellfish.
"It's also possible that nuisance algal blooms -- in particular
potentially toxic blue-green algae -- normally seen in the freshwater portions
of our estuaries will get a foothold in the surface waters of the sounds," he
said. "We are particularly concerned about Core Sound, as this is one of North
Carolina's most prized fisheries habitats."
Because water entering the Pamlico Sound system, the second largest
estuary in the United States, remains for about a year, nutrients and
pollutants washed into the system will be there long enough to affect an entire
growth cycle of algae, Paerl said. That will give a broad spectrum of algal
species the opportunity to reproduce rapidly.
Most water leaving the sound leaves by evaporation instead of through the
three narrow inlets -- Okracoke, Oregon and Barton's - that connect it with the
open ocean, he said. The sound acts like a giant bathtub trapping polluted
fresh water.
"We need to carefully and thoroughly monitor the situation immediately not
just for North Carolina's sake but also because the Pamlico Sound system
provides a nursery and refuge for the entire Southeast coastal fishery," the
scientist said. "At present, we can only speculate on the rate of development
and expansion of the dead zone and the ecosystem's ability to recover from this
catastrophic event."
In a joint effort between the Institute of Marine Sciences, the Duke
Marine Laboratory and the National Oceanographic and Atmospheric
Administration's Beaufort Fisheries Laboratory, North Carolina scientists have
begun a series of cruises to obtain long-term hydrographic, water quality and
algal growth measurements and document the sound's recovery. N.C. Sea Grant is
supporting the initial work.
Mark Sobsey of the School of Public Health and N.C. Division of Marine
Fisheries staff will test water samples for microorganisms that can cause human
disease. Pat Tester of the NOAA Fisheries Laboratory also will sample water and
monitor satellite images of turbidity, color and algal abundance.
Among the many marine species that could suffer are clams, oysters,
scallops, crabs and a variety of commercial and sport fish species, Paerl
said.
"Because of human conversion of the forests and wetlands to farmland and
urban and industrial acreage during the past few centuries, the natural
nutrient filtering capacity of the sound's watershed has been greatly reduced,"
he said. "That makes the receiving waters more prone to nutrient and other
contaminant pollution following a catastrophe like Hurricane Floyd."
Pamlico Sound's lagoon-like enclosed shape, which has made it an ideal
nursery for fish, also makes it extremely sensitive to pollution, because
substances entering the system tend to stay for a long time. In contrast,
Chesapeake Bay -- only slightly larger than Pamlico -- is a more forgiving
system since more bay water exchanges with the coastal ocean at its wide
entrance near Norfolk.
Despite its toll, some good may eventually come from Floyd, including
renewed awareness of the importance of forests and wetlands as pollutant
filters and recognition of the environmental risks associated with intensive
agricultural and urban development in coastal river flood plains, Paerl
said.
To UNC-CH Home Page