UPDATED, Sept. 3: The Arlington Board of Health issued a public-health advisory Aug. 27 for Spy Pond because of a visible algal bloom, and five days later added one for Hill's Pond at Menotomy Rocks Park.

In response, on Friday, Sept. 3, Spy Pond was chemically treated for aquatic invasive species. Swimming, boating and fishing were not permitted on treatment day, but can resume on Saturday, Sept. 4. Note that there is a five-day ban on using Spy Pond for irrigation after the treatment is applied.

The board strongly advises residents not to swim or stand in the water at Spy Pond and especially urges residents to keep pets away from the water because of the risk associated with a visible algal bloom.

Such a bloom is an overgrowth of algae in a water body that could affect water quality and aquatic life. Some blooms produced by bacteria can create toxins, which may also harm people, animals and the local environment.

Read the full advisory at arlingtonma.gov/health >>

Contact with high levels of a harmful algal blooms 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)

This news announcement was published Friday, Aug. 27, 2021, and updated Sept. 1, to add Hill's Pond, and Sept. 3.