Cyanobacteria blooms have been reported on two Rindge water bodies, according to the Department of Environmental Services.

On Wednesday, Lake Monomonac and Pool Pond had reports of cyanobacteria. Lake Monomonac had a reported sighting, with photograph, of a cyanobacteria bloom off Fourth Street on the Winchendon side of the lake. The report has not been confirmed through water testing. While the bloom was first seen on the Winchendon side of the lake, all lake-goers should be aware, as blooms can move with the wind and current.

A confirmed bloom was seen and tested on Pool Pond in Rindge. Samples were collected near Cleaves Road and the public boat launch on May 27 and analyzed May 28. The Cleaves Road test sample was above the minimum amount of cells per milliliter for safety. The bloom is a dense blue-green surface accumulation.

Cyanobacteria, sometimes referred to as “blue-green algae,” naturally occurs in most lakes, but can be harmful in high quantities. According to the New Hampshire Department of Environmental Services, it is most common in the summer and fall due to the combination of sunlight, warm water and excess nutrients. Many species of the bacteria can grow in colonies that form a “bloom” on the water that looks like a scum floating on top of the water or near the surface. While the blue-green color is best known, the blooms can range in color, including green, blue-green, yellow, white or black. 

When visible blooms are present, an advisory is put in place that the water is not suitable for wading, swimming or drinking. Exposure to the algae can cause nausea, vomiting, diarrhea, skin irritation, stomach cramps, sore throat, headache, muscle and joint pain, mouth blisters, liver damage and fever in humans and animals. Cyanobacteria blooms can be fatal to animals who drink the water or lick themselves after swimming. Anyone who has been in contact with the algae should wash it off with fresh water. Exposure can happen through ingestion, inhalation or skin contact.

The New Hampshire Department of Environmental Services tests bodies of water with cyanobacteria warnings weekly. Warnings are in effect until the bloom has passed, and water tests show fewer than 70,000 cyanobacteria cells per milliliter.

People can report suspected blooms through the New Hampshire Department of Environmental Services Cyanobacteria Bloom Report Form. The Department of Environmental Services has a Healthy Swimming Mapper for the most-current information about bloom status and severity.