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.
