Officials warn about toxic algae in North Coast rivers, lakes

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Sunscreen, hats and insect repellent aren’t enough. Add awareness of toxic algae to the arsenal of defensive tools people should have when heading to rivers and lakes for summer fun.

State Water Resources Control Board officials issued a warning last week for the North Coast, noting that high temperatures and continuing drought conditions increase the likelihood of potentially lethal algal blooms in area streams, rivers and lakes. Blue green algae, actually a cyanobacteria that gets its energy from photosynthesis and has a plantlike appearance, was responsible for three dog deaths in Sonoma and Mendocino counties last year.

Not all cyanobacteria produce toxins, but it’s difficult to tell, and water testing has been limited in scope.

The goal is public education, said Carolyn Ruttan, invasive species program coordinator for the Lake County water resources department. “It’s no different than teaching your child to wash their hands after using the toilet.”

Children and dogs are most susceptible to becoming ill because they’re more likely than adults to ingest water when swimming or playing in and along rivers and lakes. Depending on the type of toxin, symptoms can include nausea, liver or kidney failure and convulsions.

Cyanobacteria have been around for some 3 billion years, Ruttan said, but have become more prevalent and problematic in the past 10 to 15 years.

“We think it could be climate change, but we don’t know for sure,” Ruttan said. Agricultural waste, whether from commercial fertilizers or cow manure, is a known contributor to algal growth.

Clear Lake suffers regularly from algal blooms and this year is no different, Ruttan said, but so far, the blooms don’t appear to have produced toxins in dangerous amounts. Testing is periodic, however, and limited to 18 sites around the 68-square-mile lake.

A testing program was launched by the Elem and Big Valley Indian tribes following a dog’s death in 2013, said Sarah Ryan, environmental director for the Big Valley Rancheria. That dog died of microcystin toxicity, which causes liver failure. It’s the same toxin that killed at least 21 California sea otters in the Monterey Bay in 2010 and shut down Toledo’s tap water supply in 2014. The dogs that died in Sonoma and Mendocino counties last year were killed by anatoxin ­— a fast-acting neurotoxin.

Tests conducted in 2014 in Clear Lake found levels as high as 17,000 parts per billion for microcystins, Ryan said. The amount considered safe is below 0.8 ppb, she said. So far, tests this year have all been below the safe level, she said. No anatoxin has been detected.

Safety measures against the toxins include avoiding ingesting river or lake water, washing off after swimming and keeping children and dogs away from algae. But it’s not enough to avoid the obvious blooms, Ryan said.

“The toxins can be there and you don’t see a bloom,” she said.

You can reach Staff Writer Glenda Anderson at 707-462-6473 or On Twitter @MendoReporter

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