Bay Scientists Forecast “Typical” Summer Conditions for Chesapeake Bay

Ecological forecast uses historical data for glimpse into near-term Bay health

Annapolis, Md. (June 1, 2006) – Moderate weather across the Bay watershed over the past several months will likely lead to “typical” water quality in the Chesapeake Bay this summer, according to an ecological forecast developed by a team of researchers and released today by the Chesapeake Bay Program.

Based on an analysis of spring weather conditions and twenty years of Chesapeake Bay monitoring data, the ecological forecast anticipates 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.

“The forecast indicates that recent weather conditions have washed average amounts of pollution from the land and will lead to typically poor water quality this summer,” said project leader and scientist William Dennison of the University of Maryland Center for Environmental Science. “The forecast calls for ‘typical' conditions when compared to health of the Bay over the past twenty years. We need to move the needle from ‘typical' to ‘vastly improved' if we are going to have a balanced, healthy Bay ecosystem.”

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. Scientists and researchers from the University of Maryland Center for Environmental Science and the Maryland Department of Natural Resources worked with colleagues from state and federal agencies to develop the forecast.

Additional on-the-ground water quality improvement measures are needed to temper poor summer conditions that have become the norm over the past twenty years. By upgrading sewage treatment plants, planting and conserving streamside forest buffers and minimizing runoff from developed and agricultural lands, Bay Program partners are working to bring the Bay back into balance.

Anoxia - or oxygen-deprived “dead zones” - is an annual problem for the deeper waters of the Bay during summer months. Scientists forecast that 2006 summer anoxic conditions will likely be slightly better than in 2005, but rank in the middle range of the past twenty years. The impact of low oxygen levels on the Bay's crabs, oysters, fish and other living resources is difficult to predict at this time, but will be closely monitored by Bay scientists throughout the summer.

While all types of algal blooms can harm water quality, scientists are especially concerned with “harmful algal blooms” that can impact human health. The forecast suggests a moderately-high likelihood of harmful algal blooms in the tidal Potomac River this summer. Scientists have drawn a relationship between annual and seasonal Potomac River flow and the likelihood of harmful algae (cyanobacteria, Microcystis ) blooms. Scientists forecast a bloom beginning in early summer, lasting for approximately one to two months. Contact with, inhalation or consumption of water with large concentrations of Microcystis and related algal blooms can cause illness in humans and death in livestock or pets. The public will be able to view real-time water quality information for the Maryland portion of the Bay throughout the summer at www.eyesonthebay.net.

The underwater grass forecast focuses on three key areas of the Bay - the Susquehanna Flats, the lower Potomac River and Tangier Sound. Small increases are predicted for Susquehanna Flats and the lower Potomac River. In Tangier Sound, scientists anticipate some recovery from a late-season loss of eelgrass last year.

Weather plays a large role in the health of the Bay's waters, as about three quarters of nutrient pollution entering the estuary comes from polluted rainwater runoff. Nitrogen and phosphorus, the primary nutrients, come from fertilizer, human and animal wastes, and emissions from cars and power plants. When it rains, excess nutrients wash into local streams and rivers from agricultural lands, city streets, rooftops and residential lawns. The excess nutrients then flow downstream into the Bay, where they cause an overabundance of algae, resulting in deteriorated water quality. Significant algal blooms can block sunlight from reaching underwater grasses, which provide valuable habitat to local aquatic life.

While the summer forecast is built upon relationships between past environmental pressures and resulting water quality, several overriding influences - such as changes in temperature, precipitation and river flow - could impact the accuracy of the forecast. Warmer or continued wet weather could contribute to worsening conditions, while cooler and drier weather could prompt improved water quality.

The summer 2006 dissolved oxygen forecast focuses only on the deepest waters of the Bay. The overall volume of water with less than adequate dissolved oxygen concentrations - called hypoxia - is much larger. Bay scientists, however, have been unable to establish a strong enough relationship between spring rains and pollution loads to forecast this larger area of relatively low oxygenated waters.