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May 28, 2004
Bush River: Bush River Microcystis bloom intensifies.

A water sample collected from the Bush River and examined by Maryland Department of the Environment on 5/26/04 measured 500,000 cells per milliliter of the cyanophyte (commonly called bluegreen algae) Microcystis aeruginosa. On 5/27/04 Maryland Department of Natural Resources (DNR) collected a water sample during routine water quality monitoring that contained 1.4 million cells per milliliter and described the water as having the appearance of green paint spilled on the surface. The early stages of the bloom were first detected on 5/11/04 during routine water quality monitoring by the Maryland DNR (see HAB News from May 13, 2004: "Bush River: First tidewater bloom of Microcystis detected for 2004.").

Although there have been no reported cases of human illness, people should take common precautions to reduce the risk of illness or discomfort related to blue-green algal blooms:

  • The public should not swim in areas where blue-green algae bloom is evident. Do not drink water from any area with appearance of a blue-green algae bloom. Some strains of Microcystis produce toxins; gastrointestinal discomfort, heachache, diarrhea and potential liver damage may occur from ingesting concentrated bluegreen algal bloom waters.


  • If contact is made with problem water, simply wash off with fresh water. In some cases, skin irritations may occur after prolonged contact. If irritations persist, see a physician or local health care provider.


  • Keep pets and livestock away from bloom areas. Blue-green algal blooms may contain toxins that could be harmful or fatal to pets and livestock.


  • Microcystins are not known for being prone to bioaccumulation in the food chain and there are no known cases of fish-born illness from fish or shellfish taken in such bloom waters.

The Bush River was a site for a persistent summer algal bloom during 2003 beginning in late July when cell concentrations of Microcystis were 1.6 million cells/ml, Anabaena spp. was abundant (264,000 cells/ml) and a fish kill was observed (see HAB News from July 24, 2003: "Blue-green Algal Blooms Found on the Bush River."). The Bush River was just one of numerous locations where the hepatotoxin microcystin was detected in association with summer cyanophyte blooms in 2003 (see HAB News from October 30, 2003: "Microcystin toxins found across Maryland's Chesapeake Bay in summer 2003.").

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 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.