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People urged to avoid contact with water in Charles River because of toxic algae

Algae bloomed among kayaks in Broad Canal in Cambridge.
Algae bloomed among kayaks in Broad Canal in Cambridge.(Jessica Rinaldi/Globe Staff)

The Charles River Watershed Association is warning people to avoid contact with river water after discovering toxic algae this week.

River paddlers notified the association Monday that they saw blue-green algae, or cyanobacteria, growing in the river, said Lisa Kumpf, an aquatic scientist at the association. Scientists from the association then confirmed cyanobacteria were blooming in the water.

“We are officially issuing a public health advisory for toxic algae found at sites from the [Boston University] Bridge to the Museum of Science,” the association said in a statement on Wednesday.

People and pets should keep out of the water, the association said. Boaters should rinse and wash themselves thoroughly if they touch the water.

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A toxic algae has prompted warnings for boaters and swimmers in the Charles River.
A toxic algae has prompted warnings for boaters and swimmers in the Charles River.(Jessica Rinaldi/Globe Staff)

“Every effort should be made to avoid contact with the water. People should rinse off with fresh water immediately if they or their pet comes into contact with the water. If you believe you or your pet is experiencing adverse health effects, contact your doctor or veterinarian immediately,” said Marc A. Nascarella, the director of the Massachusetts Department of Public Health’s environmental toxicology program.

The DPH recommended that signs be posted along the river to warn people not to touch the water. Algae blooms are typically blue or green but can also look brown or red, Nascarella said.

“In most circumstances, direct contact with algae causes skin and eye irritation, and ingesting or inhaling small amounts are likely to cause gastrointestinal symptoms. In some circumstances, exposure to toxins has been reported to cause serious illness, or, in rare circumstances, death,” Nascarella said.

Cyanobacteria bloom in the Charles River every summer, but the association will not know if this year’s bloom is particularly severe until the DPH finishes testing the algae in a few days.

This past week’s weather conditions encouraged the algae to grow, the association said. Cyanobacteria are naturally occurring, and Boston’s summer conditions allow for algae to thrive.

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“It’s a combination of factors,” Kumpf said. “High phosphorus levels give cyanobacteria a lot of nutrients, so the recent rain last week that probably washed up a lot of stormwater and phosphorus nutrients combined with high heat from over the weekend allowed cyanobacteria to bloom and thrive in that hot environment.”


Alyssa Lukpat can be reached at alyssa.lukpat@globe.com.