CAUTION signs have been posted along public access points along the lake to advise the public of the possible presence of toxic algae in Lake Stevens. This year Lake Stevens has seen a few spot blooms of algae around the shoreline of the lake. Most occurrences have been small sized and dissipate within hours of sighting. As the weather continues to get warmer there is a concern that these may become more frequent and the duration lasting longer.
The City of Lake Stevens and Snohomish County Surface Water Management (SWM) have been on the lookout for algae blooms occurring this year on Lake Stevens. Most of the observed algae have been harmless filamentous algae which appear as green and brown free-floating mats. Recent blooms of potentially toxic blue-green algae were also detected in isolated parts of the lake from December through mid March this year. It is being advised to not do water sports or allow pets in the water near where algae scum is floating on the water surface.
Known as cyanobacteria, certain species of blue-green algae can produce toxins that affect the health of people and animals that recreate in lake water. Pets that drink lake water are of special concern. Blue-green algae scum looks like streaks or patches of blue, green, or even white paint floating on the surface of the water that will quickly dissipate if agitated.
Water samples were taken within hours of the initial confirmation of blue-green blooms. Since toxin testing takes several days and the blue-green algae blooms may come and go, CAUTION signs were posted at the public access locations around the entire lake. The signs are expected to remain posted until algae blooms are not present over several weeks.
This year the City and County approved the implementation of an algae treatment using aluminum sulfate (also known as Alum) to reduce the phosphorus in the lake. Phosphorus is the primary source of nutrients in the lake for algae growth. It is expected that this treatment will occur in late spring/early summer. In addition to this, the State Department of Ecology authorized funding an education program that will be jointly developed by the Snohomish County Conservation District, Snohomish County, and the City to encourage citizens to reduce phosphorus pollution. As a large part of the phosphorus entering the lake comes from activities performed by people at their homes, it is expected that this will help in the long term to reduce continued nutrient problems within the lake.
To find out more information, track conditions at Lake Stevens, report blooms, or sign up for email toxic algae updates visit the County’s web site at: http://www.lakes.surfacewater.info.