Green Lake algae scum found; water only harmful where scum is found
Toxic algae has been found in accumulated scum along the shores of Green Lake; however the lake is not closed and remains open to most activities.
King County Department of Natural Resources … tests have revealed that the toxins are currently found in the scummy algae that accumulate in some places along the lakeshore.
People and pets should not wade or play in the lake where the scum has accumulated. Dog owners should be especially cautious not to allow animals to drink from the lake in these areas. If there is water contact for a pet, it is important to rinse well to remove all algae.
The lake remains open to fishing, boating, stand-up paddling boarding and other recreational activities. While Seattle Parks and Recreation’s lifeguarded beaches remain open. The last day of operation for East Green Lake Beach is August 24. The last day of operation for West Green Lake Beach is September 1.
A warm, dry summer has promoted the algae bloom, and continued warm weather continues to promote it. Blooms have been known to last into November in particularly warm autumns, and typically disappear as the weather gets colder.
The lake was closed in 1999, 2002, 2003, 2012 and most recently in fall 2013 for toxic algae blooms. Intense blooms of blue-green algae have occurred in Green Lake since 1916.
Treating the lake with alum inactivates the phosphorus that is released from the bottom sediments and prevents stimulation of the algae growth. Green Lake was successfully treated with alum in 1991 and 2004. The water quality improved for several years following treatment on both occasions, and has been mostly good since 2004.
Green Lake is home to cyanobacteria, also known as 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.
Symptoms of illness from liver toxin are flu-like and may include abdominal pain, diarrhea and vomiting. If symptoms occur after ingesting lake water, park users should consult a health care professional immediately. Pets are at highest risk.
For more information on cyanobacteria, please visit Washington Department of Health toxic algae website.
(Photo of Green Lake by Alin Moni. Pretty sure that’s not the algae making all those beautiful colors.)
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