Additional testing by the King County Department of Natural Resources and Parks shows toxic levels of the cyanobacteria blue green algae scums at the lake continue to rise. Test results from samples taken on Tuesday indicate that the toxic levels in algae accumulations in some locations are higher than what was previously recorded, and are well above what is considered safe for recreational use by the Washington Department of Health’s draft recreational guidelines.
The lake remains closed to wading, swimming and “wet-water boating” activities like sailboarding. Children should not wade in the lake or play at the shoreline.
Dog owners are especially encouraged not to allow pets in the lake or to drink from the lake. The signs of toxicity in pets could be much more rapid in onset and include staggering, acute respiratory distress, convulsions and sudden death.
“Pets are the most vulnerable to the algae at Green Lake at this point,” said Seattle Parks and Recreation Acting Superintendent Christopher Williams. “Most people are not in the lake at this time of year, but dogs may still find it appealing. If a dog inadvertently goes in the lake where a scum has accumulated, it should be washed off with water from a tap as soon as possible.”
The lake is open to fishing and boating — activities in which users are unlikely to ingest the water. Eating the fish in the lake is most likely still safe, but should not be on a frequent basis. Scientists believe the toxins mostly concentrate in the internal organs of the fish, but not as much in the muscle tissue. Anyone fishing and eating fish from Green Lake should remove internal organs and wash their catch very well before cooking.
The highest levels at the lake on Tuesday were 419 micrograms per liter in a particularly heavy scum near the boat rental dock. The Washington Department of Health’s draft recreational guidelines call for 6 micrograms per liter or lower. The test was performed by the King County Environmental Laboratory under the auspices of the Washington Department of Ecology’s algae program.
“Blue green algae is buoyant and it accumulates along the shorelines because it is pushed by the wind across the lake surface,” said Sally Abella, Lead Scientist for the Freshwater Monitoring Unit of the Water and Land Resources Division at King County Department of Natural Resources and Parks.”That’s how it becomes concentrated along the shorelines. That will happen even with light, steady winds.”
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.
Warm, dry weather will promote the continuation of the bloom. Blooms have been known to last well into winter, particularly after a warm autumn. Typically, the blooms disappear as autumn progresses and the temperatures get colder.
King County scientists will continue to monitor the lake on a weekly basis. Parks will reopen the lake when three consecutive tests show the toxin has fallen below the draft recreational guideline.
Green Lake is home to photosynthetic cyanobacteria, or blue-green algae that are regularly present in small numbers. When nutrients are available and the weather is warm, the conditions are right for an algae bloom to take place. Winds 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.
The lake was closed in 1999, 2002 and 2003 for toxic algae blooms. Intense blooms of blue-green algae have occurred in Green Lake since 1916.
Testing from areas outside the scum accumulations indicates that away from the scums, toxicity is below the recreational guideline – at a level of 1 microgram per liter.
Symptoms of illness from cyanobacterial toxins can include skin rash and eye, nose and mouth irritation from contact with contaminated water. Swallowing the toxins can cause sore throat, wheezing, flu-like illness with fever, headache and muscle aches, abdominal pain, diarrhea, vomiting, and in severe cases, liver damage. Use clean water to promptly rinse skin that has been in contact with lake water. If symptoms occur after ingesting lake water, park users should consult a health care professional immediately.
For more information on cyanobacteria, please visit King County’s Major Lakes Monitoring webpage or the Washington Department of Health toxic algae website.