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Press release from the Humboldt County Department of Health and Human Services:

Environmental health officials are warning community residents to be on the lookout for harmful algal blooms after a dog died on Thursday, July 23, a short time after swimming in a slow, stagnant pool of water off the Eel River near Scotia.

Typically, warnings about cyanobacteria and harmful algal blooms (HABs) come out between late July and early August, coinciding with low flows and sustained high temperatures in the inland areas which may contribute to cyanobacteria growth in local rivers and lagoons.

While most cyanobacteria do not affect animals or people, some are capable of producing toxins that can be harmful. Dogs 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.

Freshwater HABs can appear as dark green, blue-green, black, orange or brown water or can occur as mats and sometimes create scum or foam on the riverbed or on the water. However, toxins produced by HABs may be present without visual indicators.

Officials recommend the following guidelines for recreational users of fresh water 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 toxins. Be sure to tell the doctor or veterinarian about possible contact with cyanobacteria or algal blooms.

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

Since 2001, there have been 14 documented dog deaths locally where the dogs died shortly after swimming in Big Lagoon, the South Fork Eel River or the Van Duzen River. In each instance, water samples confirmed the presence of cyanobacteria in the water. In July 2021, the confirmed presence of cyanobacteria in the Trinity River east of Willow Creek is believed to have contributed to a dog’s death that had occurred weeks before. The most recent documented event was in 2024 when two dogs died a short time after swimming in a small pool off the Eel River near Fernbridge in early September.

To learn more about cyanobacteria and harmful algal blooms, visit the state of California’s website at mywaterquality.ca.gov/habs/index.html.

To report a bloom, e-mail CyanoHAB.Reports@waterboards.ca.gov or call 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 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 blooms can also be emailed to envhealth@co.humboldt.ca.us.