The troubled waters of Indian Lake have been plagued by blue-green algae, necessitating frequent treatment, at times forcing beaches to be closed and keeping swimmers from wading in to escape the heat. That has happened again, with the city issuing a public health advisory and ordering the lake, which hosts a couple beaches, closed after the discovery of high levels of blue-green algae 

The lake will remain closed until additional laboratory tests reveal lower levels.

"Individuals and their pets are encouraged to avoid coming in contact with the lake until further notice," the city said in a statement. "The city will be working with environmental health specialists to monitor water quality and determine the length of the closure."

Blue-green algae, or cyanobacteria, are microscopic and naturally occurring in water bodies. Growth of the natural-occurring algae is aided by certain environmental conditions, including warm weather, sunlight and excess nutrients in the water. The latter can come from sources such as phosphorous and nitrogen, which are found in lawn fertilizers, storm water runoff, wild animal waste and agricultural activities.

The city said all recreational lakes and ponds are monitored for cyanobacteria, 

All recreational lakes and ponds in Worcester are monitored for cyanobacteria. The city said it will continue to monitor all bodies of water for any potential problems.

Health concerns from harmful algae blooms and their toxins vary depending on the type of exposure and the amount of toxin present. Among the health risks:

Contact with these algae can cause skin and eye irritation Ingesting small amounts can cause gastrointestinal symptoms while ingesting large amounts may cause liver or neurological damage Inhaling water spray with algae in it can cause asthma-like symptoms

 The public is advised to take the following steps until further notice:

Do not swim in the lake Do not allow pets in the water Fishing is prohibited Do not swallow water Rinse skin off immediately after contact

· Small children and pets are more susceptible to the effects of toxins than adults