Montana Harmful Algal Blooms (HAB) — NOAA Great Lakes Outlook

The current reading for this indicator updates live on the Montana Gateway dashboard. The data feed below is fetched from NOAA HAB Program · EPA / state environmental agency via the public /api/algal-blooms endpoint.

Harmful algal blooms (HABs) are excessive growths of cyanobacteria (blue-green algae in freshwater) or other algae (red tide, brown tide along coasts) that can produce toxins like microcystin, brevetoxin, or domoic acid. Blooms can poison drinking water, kill fish, and cause respiratory irritation for people on shorelines. The 2014 Toledo water crisis — microcystin contamination of drinking water for ~500,000 people — was caused by a cyanobacteria bloom in western Lake Erie.

• Do not swim, drink, or let pets enter water that looks like spilled paint, has green or red scum, or smells musty.
• If exposed, rinse skin and eyes with clean water immediately. Watch for nausea, vomiting, or skin rash.
• If your drinking water comes from a surface water source (lake, reservoir, river), check your water utility's daily advisories during bloom season.
• Report a suspected bloom to your state environmental agency (EPA / DEQ / DNR) with photos and GPS location.