City update on toxic green scum on Echo Lake

Nutrient-rich bodies of water may support a rapid growth of cyanobacteria.
When conditions are right, a body of water can scum over with a green, or blue-green growth
as shown in this photo of Anderson Lake in Jefferson County.
Photo courtesy King County

Echo Lake Algae Bloom

By City of Shoreline Staff

On September 14, 2012, City staff noticed an algae bloom on the west side of Echo lake and collected a sample.  The sample showed high levels of toxic algae called microsystins, a liver toxin.  The high levels of the toxic algae resulted in a beach closure and the posting of danger signs.  Two subsequent sampling dates showed levels below the Department of Health threshold.  

Currently Echo Lake remains at a Warning level, until the algae is no longer visibly present on the surface.

The City continues to sample and monitor the lake, until the bloom clears, or until test results are consistently within Department of Health’s guidelines.  Signs have been posted around the lake and will remain until we can assure the lake is clear of blooms.  With the current weather pattern, it is difficult to say how long we can expect the bloom to persist.

The City of Shoreline’s swimming beach monitoring program checks for algae near the swimming beach on Echo Lake every other week during summer months.   Our program also provides for opportunistic sampling anywhere on the lake and any time that a bloom is noticed.

Algae Blooms

The algae blooms of concern are commonly known as blue-green algae, or cyanobacteria. Blooms are a result of a combination of high nutrient levels, warm temperatures and stagnant water.  (Common sources of excess nutrients can come from soaps, fertilizers and mammal waste.)

There are many types of cyanobacteria. Some produce toxins that are poisonous to mammals.  There is NO WAY to tell whether the algae is toxic just by looking at it. If you suspect an algae bloom at any time, you should contact the City to have a sample tested.

The toxin found this summer in Echo Lake is microcystins, a liver toxin. People and pets should avoid ingesting and coming into contact with the water. It can cause serious illness. If a pet or you come into contact, wash the exposed area. If an animal becomes sick, the pet should be taken to the vet.  People should seek medical attention if they ingest water and then become ill.

King County provides an overview of monitoring and the toxin.

Beach Closure Determination

Several lakes have been closed this summer. A map of current closures. The last time Echo Lake was closed was in 2009.

More information can be found here.