Ephemeral 'Surface Scums' Detected At Indian Lake

WORCESTER, MA — Don't be alarmed if you see scum floating on top of Indian Lake this week.

Worcester's Sustainability and Resilience department has confirmed the presence of "surface scums" at the lake that could contain harmful cyanobacteria. The scums, however, are "short-lived and ephemeral."

"Initial testing results do not indicate levels of concern," the department said in an Instagram post Wednesday. "The city will issue a PSA if harmful levels are detected."

Indian Lake is one of the major water bodies the city monitors for contaminants. The lake received a "good" water quality score in 2023. Shore Park Beach was only closed once in 2023 due to elevated e. Coli levels, but cyanobacteria levels never came close to being a public health threat.

That's likely because the city installed an aluminum sulfate dosing station at a brook that feeds the lake to prevent algal growth. The city also dosed the lake with copper sulfate in August when there was a spike in cyanobacteria density. Cyanobacteria grow due to a combination of excess nutrients, warm weather, sunlight and slow-moving water.

People and pets who ingest cyanobacteria may experience symptoms ranging from gastrointestinal distress and irritated skin to neurological damage in larger quantities. Both of Indian Lake's beaches are closed, with the city estimating a July 1 opening date for swimming season.