HELENA—Summer is in full bloom. Before you take a dip in the lake this summer, state agencies are urging Montanans to know the health risks of Harmful Algal Blooms, or “HABs.”

HABs are caused by blue-green algae that are native to Montana’s freshwater lakes and reservoirs. Scientists believe the blooms are occurring at more locations, with increased frequency and longer duration. Causes include warmer water temperatures, longer summer growing seasons and increased nitrogen and phosphorus runoff from a variety of human activities. Under certain conditions, HABs can produce toxins that damage the skin, liver and nerve cells. They can make people sick and kill pets and livestock.

Not all varieties of blue-green algae are harmful, but some can produce dangerous cyanotoxins. Blue-green algae blooms often look like pea soup, grass clippings or green latex paint. The algae are usually suspended in the water or aggregated into floating mats. Blue-green algae are single-celled organisms, so they will not appear thread-like or stringy like roots, mosses, water plants, or green algae.

Since 2017, Montana’s HAB program partners–the Department of Environmental Quality and the Department of Public Health & Human Services–have enlisted the public’s help to track suspected HABs.

“The goal of the Montana HAB Program is to educate people about the potential dangers of HABs, how to identify them and how to respond,” said Hannah Riedl, water quality specialist at DEQ. “Because we can’t be there to track rapidly changing conditions in every water body, we want people to be informed enough to make their own decisions. We also ask the public to be our eyes on the ground and report HABs. That way, we can respond quickly and hopefully prevent people, pets, and livestock from getting sick.”