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Low levels of toxic algae remain in Tahoe Keys

Claire Cudahy
ccudahy@tahoedailytribune.com
Signs warning of potentially harmful algae blooms were posted in certain areas within the Tahoe Keys earlier this week.
Ryan Hoffman / Tahoe Daily Tribune |

Monitoring of toxic blue-green algae in several Tahoe Keys waterways is ongoing nearly two weeks after reports of the bloom came in to Lahontan Water Board.

Caution signs were posted early last week warning residents to steer clear of algae and scum when swimming and to keep pets and children away from the water. Initial testing by Tahoe Keys Property Owners Association’s water quality team showed low levels of Anatoxin-A and microcystins. Additional testing conducted by Lahontan Water Board from the waterways adjacent to properties on Aloha, Lido and Morro drives supported these results.

“We found low levels of Anatoxin-A at all three sites and microcystins at two sites,” said Doug Smith, supervising engineering geologist with the Lahontan Water Board. “We recommended to TKPOA that they keep the caution signs in place because of those levels. They are not up to the warning or danger level though.”

According to Smith, a combination of warm temperatures, sunlight and nutrient-rich water can result in a rapid growth of blue-green algae. Though a majority of blue-green algae is harmless, some produce toxins, which can cause illness in humans and animals that come in contact with it.

“We don’t know exactly all of the factors that cause it and what the reasons are that some blue-green algae are toxic and others are not,” said Smith.

Blue-green alga is not the only unwelcome aquatic organism to find its ways into the Tahoe Keys.

The 172-acres of warmer, calmer man-made lagoons in the Tahoe Keys have become prime habitat for aquatic invasive plants like Eurasian milfoil and curly-leaf pondweed, which now cover more than 90 percent of the channels.

However, with $2.4 million collected from 1,529 homeowners, TKPOA recently announced plans to ramp up treatment in hopes of reducing the weeds to a manageable level.

TKPOA water quality staff and Lahontan Water Board officials will continue to monitor the algae’s growth in the Tahoe Keys over the coming week.

As for when the toxic bloom will subside? That is a difficult question to answer, said Smith.

“It can vary widely. We could get a thunderstorm that mixes it all up, gets the water cold and kills it. It’s very hard to say. There are a lot of factors that go into it.”


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