Harmful Algal Bloom Season Beginning in California’s Waterways

With the summer season nearing and recreational activities on the state’s waterways set to increase, the State Water Resources Control Board is asking the public to be mindful of harmful algal blooms (HAB) in lakes and reservoirs, and to keep children and pets away from these HABs if they see one.

Increased water temperatures, slow moving water and excessive nutrients or organic matter cause cyanobacteria and some algae to rapidly multiply and form HABs. These HABs are blooms of cyanobacteria (blue-green algae) and are capable of producing toxins, which have the potential to negatively impact the environment, people, pets, wildlife, or livestock. Cyanobacteria are small microbes that live in nearly every habitat on land and in the water.

While visiting your local lake or river, be aware that cyanobacteria toxins can be present even though a bloom is not visible. HABs vary in color and may range from vibrant to dark green, blue-green, yellow, brown, black, or red. Not all HABs will appear on the water’s surface as some are at the bottom of a waterbody, and others float at various depths. Dogs, wildlife and children are most likely to be affected because of their smaller body size and tendency to stay in the water for longer periods of time.

Recreational exposure to cyanobacteria and associated toxins can cause eye irritation, skin rash, mouth ulcers, vomiting, diarrhea and 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. Symptoms of animal illness include: vomiting and/or diarrhea, lethargy, abnormal liver function test results, difficulty breathing, foaming at the mouth, muscle twitching and sometimes death.

The State Water Board and the nine Regional Water Boards (known as the Water Boards), in partnership with other programs and agencies, are actively supporting and coordinating a statewide HAB incident response, and have many publicly available resources. Recently the Water Boards, in conjunction with the California Environmental Protection Agency’s Office of Environmental Health Hazard Assessment and the California Department of Public Health, prepared a fact sheet to assist veterinarians to respond to incidents of suspected HAB exposure among domestic animals.

The fact sheet provides veterinarians with technical information on assessing exposure history, evaluating clinical signs, pursuing diagnosis and confirmatory testing, patient management, and reporting to proper authorities. The fact sheet is available on the California HABs Portal.

The California HABs Portal is a one-stop shop for HABs statewide and functions as a central website to share information, report a bloom, and track multiple blooms statewide. For more information, visit: http://www.mywaterquality.ca.gov/habs/

California HABs Have Met Their App

The Water Boards have collaborated with the BloomWatch App, which allows anyone observing a potential HAB to document it and send info to water managers. By using the app each user will be able to answer a few basic questions and take a few pictures of the potential HAB.

The app geotags and time stamps the data before sending all that information to the Water Boards, which alerts water managers and environmental health agencies about the potential bloom. Local agencies can then investigate the report, and post informative warning signs of the HAB if it is needed.

Enhance your recreation by adding some citizen science into the mix. Your use of BloomWatch may help prevent your neighbors from exposing themselves to a HAB and could even save a dog from dying. The BloomWatch App is available as a free download (Android, IOS).

What You Can Do to Prevent HABs

You can help prevent algal blooms in our waters by taking the following measures:

  • Be conservative with your use of water, fertilizers and pesticides on your lawn, garden or agricultural operation.
  • Avoid nutrient runoff by recycling any “spent” soil that has been used for intensive growing by tilling it back into gardens, or protect it from rainfall.
  • Create shade and filter out nutrients by planting or maintaining native plants around river banks.
  • Inspect and pump out septic systems every three to four years.
  • Prevent surface water runoff from agricultural and livestock areas.
  • Prevent erosion around construction and logging operations.

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

  • Keep pets and other animals out of the 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 these 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 these 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 the local county public health department.

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 webpage:

California Department of Public Health:

CA Office of Environmental Health Hazard Assessment: Information on Microcystin

U.S. Environmental Protection Agency: CyanoHAB website


About Kevin

Mayor - City of Oakley, Manager of Mainframe Operations and Optimization – USS-POSCO INDUSTRIES, Co-Founder and Board Member - Friends of Oakley A Community Foundation, Commissioner - Contra Costa Transportation Authority, Board Member - Tri Delta Transit, Transplan, San Joaquin Joint Powers Authority and RD 2137, Advisory Board – Opportunity Junction
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