Though it may appear to be harmless “green stuff” floating in the water, algae blooms can be toxic for humans and their pets. Working with Montana’s Department of Environmental Quality, the Bureau of Land Management’s Butte Field Office is cautioning visitors to Hauser Lake near Helena to avoid the algae, thick as pea soup, which has shown up at some of its sites.

No reports of illness have been reported at the BLM’s Hauser sites, but Butte Field Manager Scott Haight said users should exercise caution when recreating in and around the water at Hauser Lake, particularly at its White Sandy Recreation Site.

“We have posted multiple signs at our facilities, advising people about what to watch out for and what to avoid,” Haight said, noting that no BLM sites have been closed due to the blooming algae.

Harmful Algal Blooms, or “HABs,” are caused by blue-green algae native to Montana’s freshwater lakes and reservoirs, according to a recent news release from Montana’s DEQ. Potential 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 and animals sick, and at worst, exposure can be fatal.

For more information about the White Sandy site, contact the Butte Field Office at (406) 533-7600.