How can I protect myself from potential harmful algal bloom?

If you see a potential harmful algal bloom, there are things you can do to protect yourself, family and pets. There is no way to tell if an algal bloom is toxic just by looking at it. The California Water Boards recommends that you practice Healthy Habits while enjoying the outdoors at your local lake, river, or stream.

Healthy Water Habits

  • Heed all instructions on posted advisories if present
  • Avoid algae and scum in the water and on shore
  • Keep an eye on children and pets (dogs)
  • If you think a HAB is present, do not let pets and other animals go into or drink the water, or eat scum and algal accumulations on the shore
  • If you think a HAB is present, reduce potential for inhalation of sprays or mists by avoiding areas downwind of the bloom, and activities near the bloom that could kick up spray, such as boating at higher speeds, water skiing, or splashing.
  • Don’t drink the water or use it for cooking
  • Wash yourself, your family, and your pets with clean water after water play
  • If you catch fish, throw away guts and clean fillets with tap water or bottled water before cooking
  • Avoid eating shellfish if you think a HAB is present

How do I know if there is a HAB in the water?

Sometimes the bloom is easily visible, forming a "scum" or discoloration on the water surface. Other times, it is less visible, floating beneath the surface or on the bottom of a water body (benthic). Blooms can appear green, blue, yellow, red, or brown. Cyanotoxins, produced by cyanobacteria, cannot be visually detected in water or tissues. Several guidance documents are available to aid identification of algae and cyanobacteria (Fact Sheet & SOP - Bloom Observation Guide - Google Docs), and the California Freshwater HAB Field Guide is available to assist in monitoring.

How can I report a suspicious bloom, or an animal illness or human illness potentially related to a bloom?

Reporting any suspected HAB or potential HAB-related illness helps authorities understand where problems are occurring and to respond appropriately. HAB coordinators can also be contacted by phone [call: 1 (916) 341-5357 or call toll free: 1 (844) 729-6466] or email (

Learn more about Human Health Impacts, Domestic Animal Impacts and Fish and Wildlife Impacts.