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Recreating in Lakes & Streams

Officials offer advice on staying healthy while recreating in lakes and streams

LAKEPORT, CA – With warm weather in the forecast and recreational water sports gearing up, health and water resource officials across the state are reminding the public to be mindful of harmful algal blooms (HAB) in lakes, streams and reservoirs, and to keep children and pets away from these HABs if they see one.
HABHABs occur in water bodies throughout the world.   They can be recognized by several features, such as an oily or paint-like sheen on the water’s surface, benthic or floating mats, or a “pea soup” appearance of the water.   Recent HABs have been reported in Clear Lake, such as this one recently photographed from Monitor Point in the City of Clearlake.     Although HABs can occur anywhere in a body of water, in lakes they tend to be more concentrated in areas where water movement is limited and are downstream of wind and water currents and in rivers they can be found attached to the sediment on the bottom or floating along the shoreline or in backwater eddies.  

HABs are the result of a type of bacterium, known as cyanobacteria.    These microscopic organisms are an essential part of the environment and have existed for millions of years.  Typically, they live in balance with other living creatures.  When environmental conditions favor their growth, they can proliferate and accumulate in numbers that are sometimes visible to the naked eye, creating what is referred to as a Harmful Algal Bloom (HAB).  Some cyanobacteria are capable of producing toxins that can harm pets or people that come into contact with them.  Exposure can occur through direct skin contact, ingestion (eating or drinking), or breathing an aerosol of affected water.

It is important to distinguish cyanobacteria (often referred to as “blue-green algae”) from green algae and water plants that are not thought to pose potential hazards to health.   The State has created a visual guide with photos to help users recognize HABs and differentiate them from green algae or water plant growth. 

Direct exposure to a HAB, if it is toxin-producing, can result in eye irritation, skin rash, mouth ulcers, vomiting, diarrhea, or cold and flu-like symptoms.    Pets can be especially susceptible because they tend to drink while in the water and lick their fur after, increasing their risk of exposure and illness.  

This year, starting in late May, monitoring of water from shoreline sites around Clear Lake is being conducted by the Big Valley Rancheria and Elem Colony Bands of Pomo Indians.   No toxins have been detected this season to date.

The California Water Boards have collaborated with the BloomWatch App, which allows anyone observing a potential HAB to document it and send information to water managers.   In using the app, each user will be asked to answer a few basic questions and provide pictures of the potential HAB.  The public can also report the bloom directly to the California Water Boards by calling their free HAB Hotline 1-844-729-6466 or report the bloom through their online HAB Portal.

The Statewide Guidance on Cyanobacteria and Harmful Algal Blooms recommends the following for waters impacted by harmful cyanobacteria:

•    Keep pets and other animals out of the HAB-affected water. Do not allow them to drink the water or eat algal material (scum) on shore. If they do get in the water, do not let them drink the water, swim through algal material, scums or mats, or lick their fur after going in. Rinse pets in clean water to remove algal material and potential toxins from fur.

•    Do not drink, cook or wash dishes with untreated surface water from HAB-affected areas under any circumstances; common water purification techniques such as camping filters, tablets and boiling do not remove toxins.

•    People should not eat mussels or other bivalves collected from HAB-affected areas. Limit or avoid eating fish from these areas; if fish are consumed, remove the guts and liver, and rinse filets in clean drinking water.

•    Get medical treatment immediately if you think that you, your pet, or livestock has gotten sick after going in the water. Be sure to alert the medical professional to the possible contact with blue-green algae. Also, make sure to contact Lake County Public Health (707-263-1090).

Remember to always practice healthy water habits:
•    Heed all instruction on posted advisory signs
•    Avoid body contact with cyanobacteria
•    Keep an eye on children and dogs, ensuring that they do not approach areas with cyanobacteria growth
•    Do not drink untreated lake or river water.  Common water purification techniques such as camping filters, tablets and boiling do not remove toxins
•    Do not cook or wash dishes with lake or river water
•    Wash yourself, your family, and your pets with clean water after lake or river play
•    Consume fish only after the guts and liver have been removed and rinse filets
For more information, please visit:

California Harmful Algal Blooms Portal

California Cyanobacteria and Harmful Algal Bloom (CCHAB) Network
California Surface Water Ambient Monitoring Program Freshwater HAB 
California Department of Public Health

U.S. Environmental Protection Agency: CyanoHAB