Scientists with King County will be working with their colleagues from Seattle Parks and Recreation today to test experimental methods for collecting large mats of algae responsible for the toxin that has led to a recreational closure of some activities on Green Lake earlier this month.
Beginning at approximately 10 a.m. today, Oct. 9, King County and Seattle staff will attempt to use floating absorbent pads and a wet/dry shop vacuum to collect the floating algae in an effort to remove the algae blooms that are the source of a cyanobacterial toxin that has been present in elevated levels in Green Lake.
The collection is expected to occur in the northeast end of the lake, near the boat rental building. Because the toxin is concentrated in an accumulation of algae scum, King County scientists will focus on collecting and removing the algae scum accumulations.
Seattle Parks closed the lake to some activities Oct. 2 because of the presence of a cyanobacterial toxin in amounts exceeding the Washington Department of Health’s draft recreational guidelines.
The lake remains closed to wading, swimming and “wet-water boating” activities like sailboarding, with caution also going out to dog owners not to let dogs drink from the lake.
The lake is open to fishing and boating – activities in which users are unlikely to ingest the water. The closure will be in effect until the algae bloom has completed its lifecycle. This could be weeks or months, depending on the fall weather and how it affects the algae in the lake.
King County scientists will continue to take water at least once a week, and Seattle Parks will reopen the lake when the evidence of toxin falls below the draft recreational guideline.
Water quality testing is performed by the King County Environmental Laboratory under the auspices of the Washington Department of Ecology’s algae program.
Green Lake is home to photosynthetic cyanobacteria, or “blue-green algae” that are regularly present in small numbers. When nutrients are plentiful and the weather is warm, the conditions are right for an algae bloom to take place. Winds can concentrate the buoyant cyanobacteria into accumulations or scums along the shoreline, which may increase the amount of toxin that could be ingested by pets or people using the lake recreationally.
For more information on cyanobacteria, please visit King County’s Major Lakes Monitoring webpage or the Washington Department of Health toxic algae website.