U.S. Water News Online
ANNAPOLIS, Md. -- More than a third of the Chesapeake Bay
was a low-oxygen "dead zone" during monitoring in July, meaning the
nation's largest estuary is on pace to have one of its most unhealthy
summers on record, according to data.
"Dead zones" occur when fertilizer from farms and other pollutants
high in nitrogen and phosphorus are washed by rain into the bay. They
an explosive growth of algae, which die and rot. Bacteria devouring
the decaying mass consume oxygen, suffocating marine life.
A research cruise from the bottom of the bay in Virginia to its
origin at the Susquehanna River in northern Maryland from July 11 to
July 15 found that about 36 percent of the bay's central stem had
less than 5 milligrams per liter of dissolved oxygen -- the level
that rockfish and other aquatic life need.
This figure, when combined with earlier readings, puts the bay on
pace to have oxygen levels about the third- or fourth-worst they have
been in the 20 years the numbers have been closely monitored, said
David Jasinski, data analyst for the Chesapeake Bay Program, an
agency that coordinates the monitoring.
"The things we love to eat out of the bay will not do well with
this kind of summer," said Bill Dennison, an ecologist at the
University of Maryland Center for Environmental Science. "Oxygen is a
crucial part of the environment for the fish and crabs and oysters,
and having low oxygen or no oxygen is just as devastating for them as
bulldozing a forest is for other creatures."
"It's a system that's been kicked out of whack," Jasinski said.
"The fish and crabs are stressed by these low oxygen levels, but it
doesn't necessarily sign their death warrant."
About 7 percent of the bay in early July had oxygen levels of less
than 0.2 mg per liter of oxygen, classified as "anoxic" or almost
zero-oxygen, Jasinski said.
Much of the worst areas are at the deeper sections of the bay;
water closer to the surface tends to be healthier.
Larry Simns, president of the Maryland Watermen's Association,
said the low oxygen levels are much harder on oysters than on striped
bass (rockfish). These fish are being caught in good numbers this
summer, because they can swim away from the dead zones to survive.
"The only reason this isn't the worst summer ever is that there's
been very little rain," said Simns, a commercial fisherman. "If we
had a lot of rainfall in June and July, we'd be in really worse
shape," he said, saying that more rain washes more pollutants into
Beth McGee, senior scientist with Chesapeake Bay Foundation, said
the last few years of poor oxygen levels mean that the state should
approve more funding to help reduce farm runoff, the No. 1 source of
"Until we have significant increases in funding to help farmers
reduce agricultural runoff, this trend will only get worse," McGee
Delaware, Maryland, New York, Pennsylvania, Virginia, West
Virginia and the District of Columbia are in the Chesapeake Bay's
Those states agreed earlier this year to limit outflows of
nitrogen and phosphorous from wastewater treatment plants that drain
into the Chesapeake Bay in an effort to reduce such biological "dead
The U.S. Environmental Protection Agency estimated that the new
limits would stop about 17.5 million pounds of nitrogen and 1 million
pounds of phosphorus from entering the bay each year.
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