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Updated 3:00 PM August 7, 2008
 

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Large dead zones predicted for Gulf, Chesapeake Bay

Record-setting "dead zones" in the Gulf of Mexico and Chesapeake Bay appear likely this summer, forecasts from a U-M researcher indicate.

Donald Scavia, a professor at the School of Natural Resources and Environment (SNRE), makes the annual forecasts using models driven by nutrient load estimates from the U.S. Geological Survey.

In this year's Chesapeake Bay Hypoxic Volume Forecast, Scavia predicts a summer hypoxic volume of 2.4 cubic miles, the sixth-highest on record. Hypoxia refers to the loss of oxygen in water, which then leads to conditions unsustainable for aquatic life.

If the upper value of the forecast range of 3 cubic miles is reached, it will be the highest on record. The bay is about 200 miles long on the East Coast and stretches from Maryland to Virginia. It supports thousands of species of plants, fish and animals. The bay's oxygen levels are critical in determining the health of its ecosystem.

Given recent massive flooding of cities and farms in the Mississippi River basin, the Gulf of Mexico Hypoxia Area Forecast is for the dead zone to cover between 8,400-8,800 square miles of bottom waters along the Louisiana-Texas coast. If the prediction bears out, it will be the largest on record.

"The growth of these dead zones is an ecological time bomb," says Scavia, who also is director of the Michigan Sea Grant program based at SNRE. "Without determined local, regional and national efforts to control them, we are putting major fisheries at risk."

The best way to shrink the dead zones, Scavia says, is to reduce the amount of nitrogen and phosphorous flowing into these water basins.

Scavia originally developed the model to estimate the nitrogen-load reductions needed to reach particular hypoxia goals. Several years ago, he discovered that the model also could forecast the dead zone size for an upcoming season, based on the average January-May nitrogen loads for the Chesapeake Bay and average May-June loads for the Mississippi River basin.

Scavia and fellow researchers continue to refine gulf and Chesapeake Bay models, as well as develop hypoxia forecast models for Lake Erie, home of another iconic dead zone.

In these five-year studies, they are studying why dead zones occur in coastal waters and why the zones have returned to Lake Erie, how to detect the cause and ways to stop the spread before the fishery and tourism industries suffer.

In the 1960s and 1970s, the Lake Erie dead zone was a key driver for enacting the Clean Water Act and stimulating the environmental movement, Scavia says. In recent years, Erie dead zones have reappeared and expanded.

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