Coes Reservoir Closed due to Cyanobacteria

WORCESTER, Mass. - The City of Worcester Department of Sustainability and Resilience has determined there is a presence of cyanobacteria at Coes Reservoir in densities that exceed the recreational public health threshold and therefore may contain toxins harmful to humans and pets. All persons should stay out of the water, discontinue boat use and fishing, and keep pets out of the water until further notice.

Cyanobacteria are naturally occurring but can be harmful in high densities. On Aug. 7, 2026, the municipality received cyanobacteria density testing results that exceeded the state recreational threshold and are closing the lake to the public as a result. The dominant cyanobacteria present were identified as the genus Aphanizomenon and Woronichinia, which have the capacity to produce toxins. Due to these results, the Massachusetts Department of Public Health advises that the lake remains closed until further testing results show safe densities.

Indian Lake also remains under a health advisory for cyanobacteria. The municipality will continue to test both lakes for cyanobacteria and will reopen each lake when it is determined safe to do so.

Bell Pond beach and the municipality's pool and spray parks remain open.

For questions, please call the Department of Sustainability and Resilience at 508-799-8324 or visit www.worcesterma.gov/BlueSpace .