More than a third of the Chesapeake Bay was a low-oxygen "dead zone" during monitoring this month, meaning the nation's largest estuary is on pace to have one of its most unhealthy summers on record, according to data released yesterday.
"The things we love to eat out of the bay will not do well with this kind of summer," said Bill Dennison, 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."
"Dead zones" form when farm fertilizer and other pollutants high in nitrogen and phosphorus are washed by rain into the bay. These compounds feed an explosive growth of algae, which die and rot. Bacteria devouring this 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 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, a federal- and state-funded agency that coordinates monitoring.
July 2003 figures
The water wasn't as starved for oxygen as in July 2003, when researchers found 40 percent of the bay's main stem had fewer than 5 milligrams of oxygen per liter of water. That year ended up the worst on record, with a summer average of 31 percent of the bay lacking healthy levels of oxygen. The next worst was 1987, which averaged slightly less than 31 percent; and 1998, which averaged 30 percent, Jasinski said.
As the twice-monthly monitoring continues - with another team of researchers setting off in a boat yesterday morning from Solomons - researchers fear that the season-end numbers will end up close to these dismal lows. This suggests that after more than two decades of work to restore the bay, not enough is being done to halt worsening conditions, especially in the summer, when hot weather feeds bacterial growth and turns the bay into an incubator for decaying algae, researchers said.
"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, in a long wormlike shape stretching from above the Bay Bridge south to near the Potomac River. 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, explaining that more rain washes more pollutants into the bay.
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 pollution.
"Until we have significant increases in funding to help farmers reduce agricultural runoff, this trend will only get worse," McGee said.
State payments would help farmers plant trees bordering waterways and crops in the off-season to catch runoff. More farmers also need to create and follow nutrient management plans to limit the fertilizer applied to their fields, she said.
Researchers with the Maryland Department of Natural Resources and University of Maryland Center for Environmental Science send out boats to monitor oxygen levels in the bay once a month in the winter and twice a month in the summer.
The research vessels cruise the length of the bay with a crew of three or four biologists, who drop electronic meters into the water attached to cables at 22 locations, said Bruce Michael, DNR's director of tidewater ecosystem assessment.
The Chesapeake Bay Program predicted in May that this would be a bad summer, and data coming from another research cruise this month will help contribute to the analysis, Jasinski said.
"These low oxygen levels mean we still have a lot of work to do to restore the bay," said Michael. "Just upgrading sewage treatment plants won't do it. We need less fertilizer on lawns and farms, upgrades of septic tanks, storm water control systems - all of these things will reduce nutrient pollution."