NORTH COAST, Calif. – State and local public health and environmental health officials are warning recreational users of all bodies of freshwater in Humboldt, Mendocino and Lake counties to avoid contact with cyanobacteria harmful algal blooms, or HABs.
The cyanobacteria, commonly known as blue-green algae usually starts to appear in inland areas in late July or early August, coinciding with warmer weather and slower flowing water.
Most algal blooms in California contain harmless green algae, and most cyanobacteria algae do not affect animals or people. Nevertheless, health officials said it is important to stay safe and avoid contact.
A small number of cyanobacteria algae species are capable of producing toxins that can be harmful to animals and humans. Officials said dogs and children are most likely to be affected because of their smaller body size and tendency to inadvertently ingest the water or algal material.
Cyanobacteria can be present in any fresh water body. It looks like dark green, blue-green, black, orange or brown scum, foam or mats on the riverbed or floating on the water. Warm water and abundant nutrients can cause cyanobacteria algae to grow more rapidly than usual causing “blooms.”
The presence of cyanobacteria toxins has been confirmed in previous years in some water bodies within Humboldt, Mendocino, and Lake counties including the Eel River, South Fork Eel River, Van Duzen River, Trinity River, Big Lagoon, Stone Lagoon, and Lake Pillsbury.
It is, however, difficult to continuously test and monitor the many lakes and miles of our local rivers. For this reason, officials said it is important for everyone who thinks they see cyanobacteria to report it using the information provided below.
This cyanobacteria warning is being issued by the North Coast Regional Water Quality Control Board in cooperation with the Humboldt County Department of Health & Human Services, Mendocino County Environmental Health, Lake County Public Health Division and the U.S. Army Corps of Engineers San Francisco District.
Together, they recommend the following guidelines for recreational users of freshwater areas:
– Keep children, pets and livestock from swimming in or drinking water containing algal scums or mats.
– Adults should also avoid wading and swimming in water containing algal blooms. Try not to swallow or inhale water spray in an algal bloom area.
– If no algal scums or mats are visible, you should still carefully watch young children and warn them not to swallow any water.
– Fish should be consumed only after removing the guts and liver and rinsing fillets in tap water.
– Never drink, cook with or wash dishes with water from rivers, streams or lakes.
– Get medical attention immediately if you think that you, your pet or livestock might have been poisoned by cyanobacteria algae toxins. Be sure to tell the doctor or veterinarian about possible contact with cyanobacteria algae.
– Join or support one of the many watershed and river organizations.
Cyanobacteria feed on nutrients and organic matter. Human activities can have a big effect on nutrient presence in rivers, streams and lakes. Nutrients found in fertilizers, animal waste and human waste can stimulate blooms.
Excessive water diversions can reduce flows and increase water temperatures, which concentrate conditions that support cyanobacteria growth.
To help prevent algal blooms in our waters, there are several steps people can take:
– Be conservative with the 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.
To learn more about cyanobacteria algae and harmful algal blooms, including how to identify cyanobacteria algae, please visit the State of California’s “My Water Quality: Are harmful algal blooms affecting our waters?” webpage at: http://www.mywaterquality.ca.gov/habs/index.html.
To report a bloom, e-mail This email address is being protected from spambots. You need JavaScript enabled to view it. or call 1-844-729-6466 (toll free).
Blooms can also be reported via the “BloomWatch” app which is available for free download on iTunes or Google Play.
For information on conditions occurring within Humboldt County, contact Humboldt County Environmental Health at 707-445-6215 or 1-800-963-9241. Photos of suspected blooms can also be emailed to This email address is being protected from spambots. You need JavaScript enabled to view it..
Cyanobacteria warning issued for North Coast rivers and lakes
- Lake County News reports
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