Snohomish County Surface Water Management (SWM) recently found potentially toxic blue-green algae in Lake Stevens, prompting the posting of cautionary signs at boat launches and public areas around the lake. The bloom of algae was reported by citizens and samples were taken from the northwest shore and the Wyatt Park boat launch for testing. Testing results show that the liver toxin microcystin, which can sicken people and animals, has exceeded the State’s recreational guideline of 6 parts per billion. This is the first time high levels of toxins were found at Lake Stevens even though the lake was tested for toxins throughout the summer and fall.
The County and City, in coordination with the Snohomish Health District, has posted Caution signs at the public access areas of the lake. The signs warn the public not to swim in the lake, drink the water, to keep pets away from the water, to clean fish well, and to avoid areas with algae when boating.
Blue-green algae are microscopic organisms that are naturally present in lakes and streams. The algae can become abundant in shallow, undisturbed surface water that receives a lot of sunlight. When this occurs, they form blooms that discolor the water or produce surface scums. The Lake Stevens blooms appear green or blue, as if paint were lying on the surface of the water.
Some blue-green algae produce toxins that could pose a health risk to people and animals when they are exposed to them in large enough quantities. Health effects could occur when surface scums or water containing high levels of blue-green algae toxins are swallowed, through contact with the skin, or when airborne droplets containing toxins are inhaled while swimming, bathing, or showering with lake water. At this time of year, pets who may drink lake water are at the highest risk for exposure.
The County’s SWM will continue to monitor the lake weekly to track the progress of the bloom. The Caution signs will be removed from the public areas when lab results and further testing show toxin levels in the lake are below the State guideline standards for recreational usage in the lake.
For most information the County has set up a web site to provide information on Lake Stevens and some frequently asked questions at www.lakes.surfacewater.info.