The blue-green algae that bloomed in tidal rivers throughout the upper Chesapeake Bay last month was toxic, an independent laboratory has confirmed, but so far has not harmed wildlife or caused human health problems, state officials said yesterday.
Some strains of the algae, identified as Microcystis aeruginosa, can cause skin problems and flu-like symptoms in humans and can sicken or kill livestock or pets that drink it. Tests performed at Wright State University in Dayton, Ohio, confirmed the presence of the algae's toxin, said Rob Magnien, director of tidewater ecosystems assessments for the Maryland Department of Natural Resources. But, he said, it would have been harmful only in high concentrations.
The algae, which bloom in fresh or mostly fresh water, began appearing in the Elk, Bohemia, Northeast, Patapsco and Sassafras rivers, two Kent County creeks and in parts of the Potomac in early August. The state Department of Health and Mental Hygiene warned residents to stay away from the bloom.
"We knew from the beginning this was a potentially toxic species," Magnien said. "That's why the health department issued advisories to stay away from it."
Magnien said the algae appeared to be dissipating after recent storms and winds, but seemed to be making a comeback in the Sassafras after temperatures rose and winds calmed Friday.
Microcystis is a common algae that thrives in the summer months. It usually flares up when nutrient levels are particularly high. It could have been triggered by this summer's heavy rainfalls washing nutrients into bay tributaries, scientists said.
More information is available on the DNR Web site: www.dnr.state.md.us.