Toxic algal mat alert signage posted at General Creek trailhead on west shore

LAKE TAHOE, Calif. - A toxic algae mat alert sign has been posted at General Creek on the west shore after an algal mat sample collected by the California Department of Fish and Wildlife (CDFW) triggered a recommendation to post the signage.

The level of toxins measured in the dry weight of the algal mat material collected was enough for CDFW to post signage at the General Creek trailhead and other access points to alert recreators and dog walkers about the potential health risks.

Sample tests showed the presence of the cyanotoxin microcystin at levels that trigger the posting of warnings.

Recreators and dog walkers should note this situation and stay away from algal mats in the water. Do NOT let pets drink the water or eat algal mats in the water or on the shore. Keep children AWAY from algal mats and do NOT allow children to touch or eat algal mats. Algal mats can be attached to the bottom of the waterway, floating in the water, or washed up on shore. Swimming is allowed in areas without algal mats.

"There are different types of ways that algae can be sampled. Observations of the algae made by the sampling crew in the field help guide the type of sample they would collect. Typically if algae are floating in the water column (planktonic), a grab water sample would be taken. If a mat of algae appears growing from the lake/river substrate (bottom bed material) you would collect an algal mat sample," said Mary Fiore-Wagner, a senior environmental scientist with Lahontan Water Quality Control Board.

While harmful algal blooms (HABs) are caused by algae or planktonic, some algae grow attached to the bottom and can form algal mats. Some species can produce toxins, and if present, can pose a risk to humans and pets.

Do not play or handle algal mat material or let dogs in water with algal mats or near stranded mats. Learn more on how to recreate safely here: https://tinyurl.com/mujxp8zv.

Please contact the Lahontan Regional Water Quality Control Board at (530) 542-5425 if you have any questions.