This summer, as scientists with the state and federally funded Chesapeake Bay Program follow their annual ritual of reporting on the size of the low-oxygen "dead zone" in the Chesapeake Bay, they will be using a more relaxed standard of what "low oxygen" means.
Some environmentalists are concerned that the Environmental Protection Agency's move will weaken water-quality standards in a way similar to what the Ehrlich administration tried this spring, before backing off last month under heavy criticism.
"It appears to be another attempt at progress by redefinition rather than progress by consistent, measurable progress," said Erin Fitzsimmons, Chesapeake regional coordinator for the Waterkeeper Alliance.
But Richard Batiuk, associate director for science at the bay program, said the EPA's decision to change the definition of "low oxygen" after more than 20 years was made because scientific research showed deeper parts of the bay naturally have less oxygen because water circulates less at the bottom.
Instead of using a blanket standard of 5 mg of oxygen per liter of water as a benchmark for healthy water, from June 1 to Sept. 30 the EPA will use a sliding scale for most of the bay, ranging from 5 mg on the surface, to 3 mg at depths greater than about 40 feet, to 1 mg at depths greater than about 60 feet.
Batiuk said this approach is more accurate and defensible in court, if challenged by polluters who object to having to install expensive pollution-control equipment to meet the old standards. Oxygen-starved dead zones that harm marine life are caused, in part, by power plant pollution and farm fertilizer washing into the bay.
Researchers have found that centuries ago, before any farms or towns were developed around the Chesapeake, the water at the bottom of the bay had oxygen levels well below 5 mg per liter, Batiuk said.
"Water-quality standards must be legally enforceable," Batiuk said, adding that all of the states in the bay watershed are moving toward matching standards for oxygen content. "Maryland is legally obligated to meet those standards, and if those standards are not attainable, it might mean it needs to shut down all of its sewage treatment plants and keep out all of the cars ... and still it couldn't meet the standards."
