Algae are microscopic plants that are found in waterways. An algal bloom occurs when there is an excess of nutrients, particularly phosphorus and nitrogen. These nutrients often enter the waterways from runoff on lawns and farmlands.  When large amounts of these nutrients build up they overfeed the algae that exist normally in the environment and resulting in increased growth of algae and green plants. As more algae and plants grow, others die off from lack of oxygen creating even more nutrients; this causes the water to become murky and creates an unpleasant odor.

Most blooms in New England are either made up of diatoms, a common type of phytoplankton, or  blue-green algae, known as cyanobacteria. Cyanobacteria are responsible for many of the Harmful Algal Blooms (HABs) that cause ecological, economical and public health concerns in waterways, many times through the production of cyanotoxins.

Health impacts from cyanotoxins in drinking water may include fever, headaches, muscle and joint pain, blisters, stomach cramps, diarrhea, vomiting, mouth ulcers, allergic reactions, liver inflammation and hemorrhage, acute pneumonia, acute dermatitis, kidney damage, and potential tumor growth promotion. Swimming or recreating in waters with harmful algal blooms may lead to allergic reactions, including irritated eyes, ears and throat, gastrointestinal distress, and rashes and skin lesions. 

Groundwater wells do not typically produce cyanotoxins. However, there could be exceptions if your well is directly affected by surface water. If your well or spring is located within 100 feet of a lake, pond or stream, your well or spring may be under the direct influence of those bodies of water and susceptible to contamination. If you suspect an algae bloom is present switch to bottled water until the bloom has been treated or the conditions are no longer favorable to support the growth of the algae bloom.