Public Health Urges Swimmers to Beware After Dog Dies, Person Sickened By Cyanobacteria on Local Rivers | Lost Coast Outpost

Environmental health officials are reminding community residents to keep an eye out for harmful algal blooms after a report was made about a person who became ill after staying in the South Fork Eel River north of Weott. State personnel are currently taking water samples at this point and will post warnings on the coast.

That news comes days after tests of confirmed cyanobacteria, also known as blue-green algae or noxious algal blooms (HABs), were found at a location in the main Trinity River trunk east of Willow Creek and likely contributed to the death of a dog earlier this month.

Cyanobacteria can be found in any body of freshwater and look like green, blue-green, white, or brown scum, foam, or mats floating on the water. Warm water and abundant nutrients can cause algae to grow faster than usual, and these floating masses of algae, or “blooms”, can produce natural toxins that are potent and dangerous. Dogs and children are most likely to be affected because of their smaller size and tendency to stay in the water for long periods of time.

Low runoffs along several local rivers, including the South Fork Eel, Van Duzen and Mad Rivers, combined with persistently high inland temperatures and record rainfall have created ideal conditions for this noxious alga to bloom rapidly.

Since 2001 there have been 12 documented dog deaths on site, in which the dogs died shortly after swimming in the Big Lagoon, the South Fork Eel River or the Van Duzen River. In each case, water samples confirmed the presence of cyanobacteria in the water.

Most of California’s algal blooms contain harmless green algae, but the many miles of local rivers with changing conditions are difficult to test and monitor. To stay safe, it’s best to assume that an algal bloom has the potential to contain toxins.

Symptoms in humans can include eye irritation, rash, mouth ulcers, vomiting, diarrhea, and cold or flu-like symptoms. After exposure to harmful algal blooms, symptoms in dogs may include lethargy, difficulty breathing, salivation, vomiting, urination, diarrhea, or convulsions.

The following guidelines are recommended for recreational users of all freshwater bodies
in the Humboldt District:

  • Discourage children, pets, and livestock from swimming or drinking in water that contains algae foam or mats.

  • Adults should also avoid wading and swimming in water with algal blooms. Try not to swallow or inhale splashed water in an algal bloom area.

  • If you don’t see algae deposits or mats, watch young children carefully and warn them not to swallow water.

  • Fish should only be consumed after the intestines and liver have been removed and the fillets rinsed in tap water.

  • Never drink, boil or wash dishes with water from rivers, streams or lakes.

  • See a doctor right away if you think you, your pet, or livestock may be poisoned by cyanobacterial toxins. Make sure to inform your doctor or veterinarian about possible contact with cyanobacteria or algal blooms.

  • Join or support one of the many catchment and river organizations.

To learn more about cyanobacteria and HABs, visit the California State website at

To learn more about cyanobacteria and algae in the South Fork Eel River, visit

To report a bloom, email or call 844-729-6466 (toll free). Blooms can also be reported using the bloomWatch app, which can be downloaded free of charge from iTunes or Google Play.

For information about conditions occurring in Humboldt County, contact the Humboldt County Department of Health & Human Services Division of Environmental Health at 707-445-6215 or 800-963-9241. Photos of suspected flowers can also be emailed to

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