Chesapeake Dead Zone: Slightly Smaller This Summer

The annual forecast of the Chesapeake Bay's health predicts that this summer's "dead zone" of oxygen-depleted, or hypoxic, water will be slightly smaller than in recent years. However, it is still significant, according to a University of Michigan researcher and his colleagues, who conducted the research with National Oceanic and Atmospheric Administration (NOAA) support.

Their prediction that the nation's largest estuary will have a dead zone of about 1.37 cubic miles is about 10 percent below the long-term average.

The Chesapeake's hypoxic region is fed by fertilizers and livestock waste, which contribute nitrogen and phosphorus nutrients.  As a result, fish and shellfish either leave depleted waters or die.

"The size of the annual Chesapeake Bay dead zone has changed little over the past decade, which underscores the need for persistent management action to reduce the amount of nutrients flowing into the bay. The Environmental Protection Agency must keep states' feet to the fire," said aquatic ecologist Don Scavia, director of the University of Michigan's Graham Sustainability Institute, according to a statement on the University of Michigan website.

The scientists created models at the University of Michigan and the University of Maryland's Center for Environmental Science, using nutrient-level estimates and stream-flow data provided by the U.S. Geological Survey. USGS estimates that 58 million pounds of nitrogen ran into the Chesapeake Bay from January to May 2015, which is 29 percent below average conditions.

That result is attributed to low river flow and below-normal nutrient run-off from the Susquehanna River this spring, researchers said. Other causes behind dead zones are nutrient-rich waters that create algae growth, which consumes oxygen; and wind speed and direction, precipitation amounts, and temperature.

The size of the Chesapeake's dead zone has been measured annually since 1950.