A water sample collected on July 28th from the Bush River system, upper Western Shore of Chesapeake Bay, tested positive for microcystin toxins at Dr. Wayne Carmichael's Wright State University laboratory. Water samples were dominated by the toxigenic phytoplankton species Microcystis aeruginosa. Toxin concentrations reported this week were greater than World Health Organization drinking water quality guidelines (1 µg/L) for human health safety from long term, chronic toxin exposure. However, toxin levels are lower than concentrations observed in September 2000 samples from another blue-green algal bloom event on the Sassafras River (see HAB News from August 13, 2003: "Microcystin toxin present in the Sassafras River blue-green algal bloom; DNR Press Release.").

The sample collected from the Bush River on July 28th, 2003, showed an average microcystin concentration of 107 µg/g dry weight of algae and 31.3 µg toxin/L of water volume. These levels are approximately 10-times greater than the toxin concentrations found in samples collected from the Sassafras River on July 22nd. Toxin levels of four samples collected from the Sassafras River on September 12, 2000, ranged from 591 to 1041 µg/g dry weight of algae; those microcystin levels were considered moderate to high concentrations.

Maryland Department of Natural Resources is working in cooperation with Department of the Environment, Department of Health and Mental Hygiene and Department of Agriculture to continue monitoring the blue-green algal bloom conditions in the Bay. The Maryland DNR website Eyes on the Bay further provides locations for tracking active algal blooms and near real-time water quality conditions throughout the Chesapeake and Coastal Bays.