Agencies testing for toxic blue-green algae on South Shore of Lake Tahoe

Officials are waiting for test results to determine if toxic blue-green algae is present in Lake Tahoe.
Justine Dhollande / Tahoe Daily Tribune
INCIDENTS IN CALIFORNIA Click here to view a map of reported incidents in California. Click here for more information on harmful algal blooms.

Officials are awaiting test results to determine if a toxic form of algae is present on the shoreline of Lake Tahoe.

A person reported late Wednesday, Aug. 21, that their dog had died after swimming in the lake near the Tallac Historic Site on Tahoe’s South Shore, according to Doug Smith, assistant executive officer with the Lahontan Regional Water Quality Control Board.

Staff from Lahontan and El Dorado County visited the site the following day to take samples from the area where the owner said the dog was swimming. 

In many cases a potentially harmful blue-green algal bloom is visible on the surface of the water. Staff did not see signs of a bloom, but they proceeded to take multiple samples, Smith told the Tribune.

The test results are expected around the end of the week. Those results will dictate what action, if any, will follow.

“The test results will drive what we do next,” said Lisa Herron, public affairs specialist with the U.S. Forest Service Lake Tahoe Basin Management Unit. The historic site and adjacent Kiva Beach, which is one of a handful of dog-friendly public beaches in Tahoe, are located on Forest Service land. 

As a precaution, signs have been posted in the area near the Tallac Historic Site alerting visitors of the possible presence of toxic algae. 

The caution signs at the bottom of this photo are posted at the Tallac Historic Site.
Justine Dhollande / Tahoe Daily Tribune

However, Smith said he regularly visits Kiva Beach with his dog and has seen zero signs of toxic algae.

“I don’t see any reason to not take my dog out to Kiva,” he said.

The important point, he added, is to be on the lookout for surface scum that is green and/or blue in color and resembles spilled paint. If there is algae in the water then it is best to avoid it.

Can be fatal for dogs

Blue-green algae, also known as cyanobacteria, occurs naturally in bodies of freshwater, but under certain conditions the algae can grow rapidly in what’s known as a bloom, according to the California Water Quality Monitoring Council.

Some algae produces harmful toxins that can pose health risks to humans and animals. In some cases, exposure can prove fatal in animals.

Dogs are especially susceptible to harmful algae because they consume more water while swimming and playing in the water, according to the Monitoring Council. And unlike humans, they are not as easily deterred by the sight and smell of the algae.

Symptoms of exposure to toxic algae include excessive salivation, vomiting, fatigue, staggered walking, difficulty breathing, convulsions and liver failure, according to the Centers for Disease Control and Prevention. In serious cases, the exposure can prove deadly within hours or days.

If your pet experiences symptoms after possible exposure to blue-green algae, contact your veterinarian immediately.

Source: California Water Quality Monitoring Council

Health risks posed by blue-green algae grabbed national attention earlier this month when local news station WECT reported that three dogs died just hours after playing in a pond in North Carolina. The report said blue-green algae was responsible for the animals’ death.

Another dog in Georgia died days later after swimming in a lake, according to local station WXIA-TV.

There were 25 domestic animal deaths and eight human incidents of illness related to harmful algal blooms in 2017, according to the California Water Quality Monitoring Council.

It is unclear if exposure to algae was responsible for the death of the dog in South Lake Tahoe. Smith said an autopsy was not performed and the dog has since been cremated.

“It’s really unfortunate and sad that the dog passed away,” Smith said.


The occurrence of blooms is increasing in California. The Monitoring Council notes that stagnant water, sustained high temperatures and increased intensity and duration of sunlight can lead to ideal conditions for algal blooms.

For those reasons, Smith said Tahoe does not fit the bill for an ideal site to host a toxic algal bloom.

“You wouldn’t expect to find it in the splash zone,” Smith said, referring to the area of shoreline where the dog was reportedly swimming.

An example of a more ideal location is the Tahoe Keys.

Earlier this month caution advisory signs were posted at lagoons in the Keys after routine water monitoring by the Tahoe Keys Property Owners Association detected low concentrations of cyanotoxins.

Continued testing found elevated levels of the cyanotoxins in some areas, per an Aug. 20 update.

According to the advisory, children and dogs should avoid areas with visible surface blooms in the Keys.

California Water Quality Monitoring Council
California Water Quality Monitoring Council

As of Monday afternoon Smith said the Lahontan Board was unaware of any additional reports of harmful algae in the Tahoe Basin.

Earlier this month, Alpine County notified the public that elevated algae levels were detected in Red Lake and Indian Creek Reservoir. The county advised the public to avoid contact with both bodies of water.

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