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Potentially Harmful Algal Bloom on Charles River 8/20 Update

August 20, 2015

Water samples collected on Aug. 17 at the Weld Boathouse and the public dock near Community Boating showed that levels of cyanobacteria (blue-green algae) had decreased and were now below the state's guideline level. 

On Aug. 13, state health officials notified the Cambridge Public Health Department that a water sample collected at Magazine Beach in Cambridge showed cyanobacteria concentrations roughly double the state’s guideline level. The algal bloom was believed to extend from the Weld Boathouse near Harvard Square downstream to the Charles River Dam near the Museum of Science, according to the Charles River Watershed Association.

Microcystin toxins—commonly released by cyanobacteria—were not detected in any Charles River water samples taken this week or last.  

The Massachusetts Department of Public Health will do a second round of testing during the week of Aug. 24-28. If these new samples have levels of cyanobacteria below the guideline level, the algal bloom advisory will be lifted. The Cambridge Public Health Department will announce test results next week.

Until the advisory is lifted, the Cambridge Public Health Department recommends that people and pets avoid contact with the algal bloom. For tips and resources, see the Aug. 14 advisory from the Cambridge Public Health Department.

For more information, contact the Massachusetts Department of Public Health at 617-624-5757 or visit www.mass.gov/dph/environmental_health. You can also contact the Cambridge Public Health Department at 617-665-3838.

Suzy Feinberg, MPH
Public Information Officer

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