Slight Improvements Observed In Chesapeake Bay's Health During Summer

On Nov. 9, the Chesapeake Bay Program announced that three key measures of Chesapeake Bay health showed minor improvements during the 2006 summer months compared to a year ago.

Summer dissolved oxygen levels, an essential measure of water quality for nearly all bay species, were somewhat better in 2006 than during the same period last year. However, the levels are still typical of the generally poor water quality that affects the Chesapeake every summer. According to bay scientists, vital underwater bay grasses may be showing areas of improvement, but important beds in the lower bay have not fully recovered from major losses in the late summer of 2005.

Researchers also examined the extent and duration of harmful algal blooms that regularly hit Potomac River waters and found mixed results. Researchers had predicted a moderately high likelihood of harmful algal blooms in the tidal Potomac River this summer. Scientists predicted a bloom that would begin in early summer and last one to two months. However, the harmful algal blooms started in late summer and lasted 1.5 months. The blooms reached 26 miles from the onset, which was measured at Blossom Point on July 26. The arrival of Hurricane Ernesto weather ended the growth.

In May, scientists and researchers released their 2006 ecological forecast for the bay, predicting "typical" conditions in three key areas relating to overall Chesapeake Bay health.

"Based on an analysis of spring weather conditions and 20 years of Chesapeake Bay monitoring data, the forecast anticipated the annual return of oxygen-deprived 'dead zones' in the bay's deeper waters, slight increases in beneficial underwater grasses and a moderately high likelihood of harmful algal blooms on the tidal Potomac River," said Bill Dennison, vice president of science application, University of Maryland Center for Environmental Science. He also is the chairman of the Bay Program's Tidal Monitoring and Analysis Workgroup (TMAW), which was largely responsible for the forecast.

Spring 2006 weather conditions were considered extreme, with lower than average rainfall from mid-February to mid-May. The region was deluged at the end of June with rainfall leading to the 100-year-flood mark in some areas. The remainder of the summer weather was "fairly average" until August, when the remnants of Hurricane Ernesto washed into the area, bay researchers said.

"Summer conditions are determined largely by the pollutant load washed into the bay by rain in the preceding winter and spring," according to Carlton Haywood, chairman of the Bay Program's monitoring panel and director of program operations for the Interstate Commission on the Potomac River Basin. "The health of the bay in the critical summer season will improve as we take action in the fall to reduce the level of pollutants in the watershed. Planting winter cover crops that stop pollutants from washing into local rivers with spring rains is just one of many practical actions we can take that will have a positive impact on the Chesapeake."

For more information, visit the Chesapeake Bay Program's Web site at

This article originally appeared in the 11/01/2006 issue of Environmental Protection.

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