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August 29, 2003
Blue-green algal bloom hotspots: Sassafras River, Upper Bush River and middle Potomac River and tributaries.

On August 28th, surface scums and shoreline accumulations of blue-green algae, dominated by Microcystis aeruginosa, were most evident in the Sassafras River and tributaries from the river mouth to Galena and Georgetown during an aerial survey of the upper Chesapeake Bay. Betterton Beach on the Sassafras River remains closed as a result of persistent blue-green algal blooms. Additional testing since July 22nd by Dr. Wayne Carmichael's Wright State University laboratory and Delaware's Department of Natural Resources and Environmental Conservation showed four positive tests for microcystin toxin from the waters of Tucker Creek and the main Sassafras River down to Betterton Beach.

Boat surveys by Maryland DNR on the Bush River found similar thick algal blooms in the upper reaches of this river system. Two toxin tests on water collected from the Bush River were conducted by Dr. Carmichael's Wright State University laboratory and were positive for microcystin. MDE reports today, August 29th, and additional citizen observations indicate blue-green algae are also concentrated in the middle Potomac River this week as far south as Route 301 bridge at Morgantown.

No surface concentrations of blue-green algae were observed on the Chester River, Fairlee Creek, Bohemia River, Lower Elk River, Northeast River, Lower Patapsco, Lower Magothy, Severn below Round Bay and the Lower South River.

Boat surveys were conducted Tuesday and Wednesday (August 26th and 27th) on the Severn, Magothy and Chester Rivers. There was no visible evidence of blue-green algal blooms in these rivers. Aerial surveys on August 28th supported the findings. Some nontidal ponds adjacent to the Bay were observed to have algal blooms, most notable is a pond between Fairlee and Worton Creeks in Kent County.

Monitoring surveys are extensive in their coverage of the tidal waters of our Bays. Aerial surveys further enhance our ability to observe the health of the Bay. However, the coverage is not exhaustive of all Bay waters. Pockets of blue-green algal blooms may be encountered during boating and other recreational activities. Cases of human illness this year have included itching, rashes and stomach discomfort from contact with or ingestion of bloom waters. 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 the 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.

The Maryland Department of Natural Resources will continue to monitor all Microcystis blooms throughout the state. For up to date information on all of Maryland's harmful algal blooms and water quality, please visit Eyes on the Bay.