Sonoma County officials posted caution signs at beaches up and down the Russian River on Wednesday alerting visitors to positive test results for a potentially dangerous, naturally occurring neurotoxin linked to harmful algae, a problem surfacing around Northern California this summer.
Water samples collected at three local beaches turned up very low levels of a substance called Anatoxin-a, which is produced by certain species of blue-green algae, Sonoma County health officials said.
It’s the third year in a row the algae-related toxin has been detected in the river.
The most-recent samples were taken Monday and the test results received Wednesday, Sonoma County Health Officer Karen Milman said.
Though the level of toxin in the water “was just at the ability to detect it,” the finding triggers precautionary alerts under state guidelines, she said.
Rivergoers should be particularly watchful of dogs, which are actually attracted to harmful algae, according to studies, and, by virtue of their relative body size and habits when around fresh water, are particularly susceptible to exposure.
But swimmers, waders, tubers, paddle boarders and others who may have direct contact with water, as well as parents of small children, should take precautions to ensure they do not put themselves or their offspring at risk, health officials said.
That means avoiding ingesting river water or cooking with it, washing off after swimming and avoiding hand-to-mouth contact.
“Be aware and take precautions to protect themselves, particularly their pets, but also know that the river is open,” Milman said.
The news, if not entirely surprising, is disappointing for business owners dependent on the river, coming at high season for tourism.
After three consecutive years, and with the toxin levels so low, many said they thought most visitors would continue to enjoy local beaches and boating, though some unknown number will stay away, they said.
“I think the newness of these warnings has warn off, so people realize that the risk is low,” said Dan Poirier, co-owner of Johnson’s Beach & Resort in Guerneville.
John Menth, a county parks lifeguard who also runs his own paddle boarding rental and tour company, said he was at Healdsburg’s Veterans Memorial Beach on Wednesday when county personnel came to post the caution signs.
Some arriving visitors “turned right around and left,” he said, forecasting some impact on river business.
But he and others said they hoped people would understand they are not at risk “if they don’t go down there and drink the water.”
The Russian River notification comes in the wake of a broader alert from the North Coast water quality regulators about the potential for harmful algal blooms in fresh water bodies around the region — including Lake, Mendocino and Humboldt counties — as a result of summer conditions that include warming water temperatures and slow-moving water.
Algae-related toxins already have been reported at several sites around Northern California this year, including in Clear Lake and in Upper and Lower Blue Lakes, all in Lake County.
Blue-green algae is reportedly widespread in Clear Lake, though samples that tested positive for toxins in early July were at very low levels, mostly from the most southerly parts of the lake, according to Sue McConnell, a program manager with the Central Valley Regional Water Quality Control Board, with jurisdiction over most of Lake County.