Worcester Closes Indian Lake After Cyanobacteria Exceed Recreation Threshold

Worcester closed Indian Lake to public recreation on Aug. 4 after testing found cyanobacteria densities above the state recreational public-health threshold.

The city said the lake will remain closed until further testing shows safe conditions. Residents should stay out of the water, discontinue boating and fishing, and keep dogs and other pets away from the water until further notice.

What is prohibited at Indian Lake

The City of Worcester Department of Sustainability and Resilience said people should stay out of Indian Lake, stop using boats and fishing, and keep pets out of the water.

The closure affects a waterway with public recreation access in Worcester. Massachusetts Fish and Wildlife identifies Indian Lake as a 204-acre great pond in the northern part of the city, between Interstate 190 and Route 122A. The city manages a paved boat ramp at Morgan Park. Cartop boats can also be carried in at Indian Lake Park and Shore Park, and shore fishing is available at the public access locations under normal conditions.

What the city found

According to the city’s Aug. 4 notice, Worcester received cyanobacteria density testing results that exceeded the state recreational threshold. The dominant cyanobacteria identified were the genera Microcystis, Planktolyngbya and Aphanocapsa.

The city said those genera have the capacity to produce toxins harmful to humans and pets. The notice does not say that toxins were detected at Indian Lake, and it does not report illnesses or confirmed exposure connected to the closure.

Cyanobacteria, sometimes called blue-green algae, occur naturally in freshwater. When concentrations become high, some types can produce cyanotoxins that may harm people and animals through contact with or ingestion of contaminated water. Worcester’s monitoring guidance cautions that the presence of cyanobacteria alone does not establish that toxins are being produced.

Why the closure may continue

Massachusetts Department of Public Health guidance recommends issuing a recreational-water advisory when conditions such as visible cyanobacteria scum, cell counts above the state threshold or toxin levels above guideline values create a potential health risk.

DPH recommends rescinding an advisory after two successive samples, collected a week apart, show cell counts or toxin levels below the applicable quantitative guideline values. That means the Aug. 4 closure is based on current testing and is not a permanent determination about Indian Lake.

Worcester said it will continue testing and reopen the lake when it is determined to be safe. The city has not announced a reopening date.

What residents should do

Residents should avoid swimming, boating, fishing and other contact with Indian Lake while the closure remains in effect. Pets should be kept away from the water and from visible scum or other material they could ingest.

If a person or pet is exposed to water that may contain cyanotoxins, the city’s monitoring guidance recommends rinsing with tap water immediately. Do not let pets lick their fur after exposure. Owners should contact a veterinarian if an animal ingests lake water or surface material that may contain cyanobacteria.

Residents can monitor Worcester’s Cyanobacteria Monitoring Collaborative page and the city’s official announcements for sampling updates and any reopening notice. The monitoring page lists Indian Lake among the waterways tracked by the program and links to recent results.

The most recent monitoring record listed before the closure was dated July 18. That supplemental WCMC report rated both the Clason Beach and Morgan Park sampling locations at Indian Lake as elevated overall risk. The report says its methods are not certified by Massachusetts and that WCMC does not measure cyanotoxins, so it should not be treated as the Aug. 4 closure test.

Sources

• Indian Lake Closed due to Cyanobacteria — City of Worcester
• Guidelines for Cyanobacteria at Recreational Freshwater Locations — Massachusetts Department of Public Health