Health and Wellness

High Levels of Bacteria Found in Upper Mystic Lake


High levels of cyanobacteria (blue-green algae) were detected in the Upper Mystic Lake during a recent water sampling conducted by the Massachusetts Department of Public Health, town Public Health Director Natasha Waden reports.

This kind of algae can be toxic if ingested in high doses and can cause skin irritation after wading or swimming. The Arlington Board of Health strongly advises residents not to swim or stand in the water and urges pet owners to keep their animals away from the water.

Contact with high levels of the cyanobacteria algae has been found to contribute to eye, ear and skin irritation. During an algae bloom, the amount of algae and toxin in the water can become elevated and exposure can be potentially harmful to people and animals. Ingestion of elevated concentrations of the algae and its toxin can lead to more serious health effects (e.g., muscle cramps, twitching and liver damage).

The state collected the sample from a part of the lake in Winchester last week, following a report from a resident that algae had bloomed in the body of water. Arlington officials received notification of the high levels of cyanobacteria on Monday, July 10, and provided a news release two days later.

Cyanobacteria algae grows naturally beneath or on the surface of many bodies of water. Under certain conditions — such as warm weather and an abundance of nutrients in the water — the algae may experience a significant amount of growth that results in dense, floating mats of it throughout the water. This is commonly referred to as an “algae bloom.”

“To prevent sickness and skin irritation, we strongly advise community members and those with pets to avoid contact with Mystic Lake,” Waden said in the release. “We will be monitoring this situation closely and will let the public know as soon as it’s safe to resume activities in the lake.”

The state will continue to collect samples weekly until cell counts drop to safe levels, at which point the Arlington Board of Health will notify the community.

Ironically, a U.S. Environmental Protection Agency report card released in June reported the water quality at the Upper Mystic Lake during 2016 at A-plus.

Involved in collecting samples are the Mystic River Watershed Association, based in Arlington, and the Massachusetts Water Resources Authority.

Photo courtesy Mystic River Watershed Association

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