Skip to Main Content
July 24, 2003
Blue-green Algal Blooms Found on the Bush River.

A blue-green algal bloom consisting largely of Microcystis and Anabaena was identified by Maryland Department of the Environment (MDE) personnel on July 23rd on the Bush River, an upper western shore tributary to the Chesapeake Bay. In an area where the algae were concentrated along the shoreline from the winds and currents, algal concentrations of Microcystis were estimated at 1.6 million cells/ml, similar to initial samples collected on July 18th on Turner Creek (Sassafras River). Anabaena was also large fraction of the sample estimated at 264,000 cells/ml. About 1,800 fish that appeared to have been dead for several days, consisting largely of gizzard shad (Dorosoma cepedianum) were observed over a stretch of 2.5 miles of the Bush River.

Microcystis and Anabaena may contain toxins that can cause health problems in humans and animals that come in contact with or drink the water. Maryland Department of Natural Resources collected samples of Microcystis from the Sassafras River on July 22, 2003 and have submitted them to laboratories for analysis of toxin content. Results are expected in two to three weeks. Environmental conditions may be appropriate for the development of blooms in other parts of the upper Chesapeake Bay as the summer progresses. In hot weather, and especially in still water with high levels of nutrients, blue-green algae can grow and accumulate rapidly, causing a bloom. 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.
     
  • 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.
Blue-green algae naturally occur in tidal freshwater portions of the Chesapeake Bay and its tributaries. However, algal blooms may periodically use up oxygen, causing fish to suffocate and die. Affected waters may also appear as if a blue-green to yellow-green paint is floating on the surface of the water. Major blue-green algae blooms were last reported in the upper Bay region in 2000.

A Press Release regarding conditions on the Sassafras River was published by Maryland Department of the Environment July 22nd and may be referenced for further information on blue-green algal blooms in the upper Chesapeake Bay. A fact sheet on Microcystis and the 2000 bloom can be found on the Department of Natural Resources' website. Maryland Department of Natural Resources and Environment will continue to monitor the situation and publish updates to the website as necessary. To report a fish kill or fish health related event, please call the Fish Health Hotline at (888) 584-3110, 24 hours a day.