Key Chesapeake Measures Show Slight Improvement

Annapolis, Md. (November 9, 2006) - Three key measures of Chesapeake Bay health showed minor improvements during the 2006 summer months compared to a year ago, according to data released today by the Chesapeake Bay Program.

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. Vital underwater bay grasses may be showing areas of improvement, according to Bay scientists, but important beds in the lower Bay have not fully recovered from major losses in the late summer of 2005. Researchers also looked at the extent and duration of harmful algal blooms that regularly hit Potomac River waters and found mixed results.

In May, Bay 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 twenty 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 and chair of the Bay Program's group that 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 then 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.

“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, chair 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 .”

The forecast, compared with the actual observations are highlighted below:

Dissolved Oxygen

Forecast: Anoxia - or oxygen-deprived “dead zones” - is an annual problem for the deeper waters of the Bay during summer months. Scientists expected that 2006 summer anoxic conditions would rank in the middle range of the past twenty years. Scientists forecast that the average anoxic volume would be 1.08 km3.

Actual: The 2006 forecast was exceptionally accurate. In fact, 2006 ranks as the 7 th best year for anoxia in the past 21 years. On average, the amount of anoxia in the Bay's mainstem this summer was 0.93 km3, or 1.79 percent. This figure is a significant improvement from 2005, which was the fifth worst summer on record. However, the volume of anoxic water, even if better than average, is still worse than the long term goal, which is to reduce anoxia to close to zero.

Underwater Bay Grasses

Forecast : Slight increases in underwater bay grasses were forecast for the northern Bay and lower Potomac Rivers, along with a partial recovery of eelgrass in Tangier Sound.

Actual: The beds in the Northern Bay may have increased more than expected and the beds in the Potomac River had mixed results. The aquatic grass in Tangier Sound may have experienced some recovery in 2006. Final survey results enabling a conclusive assessment of the forecast will be available in early 2007.

Harmful algal blooms

Forecast: The forecast suggested 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.

Actual: In actuality, there was an onset of harmful algal blooms in late summer, as opposed to early summer. The bloom lasted 1.5 months and reached 26 miles from the onset measured at Blossom Point on 26 July. The arrival of Hurricane Ernesto remnants ended the growth.

Scientists and researchers from the University of Maryland , the Virginia Institute of Marine Science and the Maryland Department of Natural Resources worked with colleagues from Federal and other state agencies to develop the Summer 2006 forecast as well as conduct monitoring of conditions throughout the summer. “The forecast provides resource managers and the public with an improved context for understanding Bay water quality conditions and offers additional guidance to Bay restoration leaders,” concluded Haywood. “However, if we are going to have a balanced, healthy Bay ecosystem, we need to break this ‘typical' cycle and begin to show vast improvement.”