For questions about the King County  Major Lakes Monitoring Program, please contact Sally Abella (206) 477-4605, or Debra Bouchard (206) 477-4650.

King County’s Toxic Cyanobacteria Monitoring Programs

In the fall of 1997, a toxic bloom of Microcystis aeruginosa in Lake Sammamish led to part advisories at Lake Sammamish State Park, Idylwood Park, and Marymoor Park. An extensive study conducted in 1999 revealed a toxin producing bloom despite the absence of a visible accumulation of cyanobacteria. Green Lake was closed due to a toxic algae bloom (shown in aerial view) in 1999.

These events prompted the King County Science and Technical Support Section to include cyanotoxin monitoring as part of its Swimming Beach Monitoring Program. This cyanotoxin monitoring effort is conducted at each of the 17 monitored swimming beaches. Samples are collected weekly from March through October.

The objectives of the King County Cyanobacteria Toxicity Monitoring Program are to:

  • Evaluate the presence of microcystins, a hepatoxin, and anatoxin-a, a neurotoxin, to protect human health
  • Estimate concentrations and geographic extent of the toxicity, should it be present
  • Establish relationships between microcystin and cyanobacteria species/abundance.

King County’s Cyanotoxin Monitoring Program takes a proactive approach by testing for toxins routinely, and when cyanobacteria blooms or scums appear, at public beaches. Working through Seattle-King County Public Health, a beach will be posted when cyanotoxins are measured at significant levels.

In addition, the King County Science Section is playing a major role in a regional wide monitoring of toxic algae. Beginning in 2009, King County, in conjunction with the State Department of Ecology, State Department of Health, Snohomish and Pierce counties, is participating in a tri-county project to understand and quantify the extent of toxic cyanobacteria blooms in our lakes. This project is funded through a grant from the Center for Disease Control (CDC).

King County’s participation in these cyantoxicity monitoring efforts will provide decision-makers with information and recommendations regarding recreational water use during cyanobacterial blooms and will lead to improved management of County lakes for the protection of human health.

Regulatory Status of Cyanotoxin Criteria and Guidelines

In 2005, the Washington State Legislature established funding for a Freshwater Algae Control Program (RCW 43.21A.667) through the Department of Ecology (Ecology) to assist local governments in the management of freshwater algae problems. As part of this program Ecology partnered with the Washington Department of Health (WaDOH) to develop recreational guidelines values for cyanotoxins. WaDOH has recommended a three-tiered approach using the recreational guidance values of 6.0 µg/L microcystins and 1 µg/L anatoxin-a for managing Washington Lakes (WaDOH, May 2008). More information about this three-tiered management approach can be found at the Washington State Department of Health webpage.

As Washington lakes and their watersheds are developed, and as periods of thermal stratification increase (see Status and Trends) more frequent and persistent problems are seen with algae throughout the state. The Washington Department of Ecology (Ecology) and many other jurisdictions are currently monitoring algae concentrations in waters across the state. To learn more about statewide efforts visit Ecology’s Toxic Algae Control home page.

Blue-Green Algae Blooms

Cyanobacteria, formerly called "blue-green algae", are simple, life forms closely related to bacteria. Although they are similar to algae, they are not true algae. Cyanobacteria are found throughout the world in freshwater and marine habitats. However, cyanobacteria "blooms" typically only occur in freshwater.

blue breen algae bloom

Nutrient-rich bodies of water such as eutrophic lakes, agricultural ponds, or catch basins, may support a rapid growth of cyanobacteria. When conditions are right, a "clear" body of water can become very turbid with a green, blue-green or reddish-brown growth within just a few days as shown in this picture of Anderson Lake in Jefferson County.

Toxic Cyanobacteria

Sometimes cyanobacteria blooms may produce toxins that are potentially lethal to animals, including humans. Cyanotoxins include a diverse range of toxic mechanisms as illustrated in Table 1. Poisoning from nerve toxins can appear within 15-20 minutes after ingestion. In animals symptoms from neurotoxin exposure include weakness, staggering, difficulty in breathing, convulsions and death (DOH 2000). In people symptoms may include numbness of the lips, tingling in fingers and toes, and dizziness. Liver toxin poisoning may take hours or days for symptoms to appear. Symptoms of liver toxin exposure include pain, diarrhea and vomiting in humans and death in animals.

Table 1. General features of cyanotoxins. (Modified from Chorus and Bartram 1999.

Toxin Group Primary Target organ in mammals Cyanobacterial genera
Microcystins Liver Microcystis, Anabaena, Planktothrix (Oscillatoria), Nostoc, Hapalosiphon, Anabaenopsis
Nodularian Liver Nodularia
Anatoxin-a Nerve Synapse Anabaena, Planktothrix (Oscillatoria), Aphanizomenon
Anatoxin-a (S) Nerve Synapse Anabaena
Aplysiatoxins Skin Lyngbya, Schizothrix, Planktothrix (Oscillatoria)
Cylindrospermopsins Liver Cylindrospermopsis, Aphanizomenon
Lyngbyatoxin-a Skin, G.I. Tract Lyngbya
Saxitoxins Nerve Axons Anabaena, Aphanizomenon, Lyngbya, Cylindrospermopsis
(LPS) Potential irritant; affects any exposed tissue ALL

Human health risk from exposure to cyanobacteria and their toxins during recreational water use arises through three routes of exposure (WHO):

  • direct contact of exposed parts of the body, including sensitive areas such as the ears, eyes, mouth and throat, and the areas covered by a bathing suit (which may collect cell material);
  • accidental uptake of water containing cells by swallowing; and
  • uptake of water containing cells by aspiration (inhalation).

It is not possible to determine whether it is producing toxins without special testing. Therefore the State is warning people (and their pets) to avoid contact with surface scums whenever a blue-green bloom is suspected (Ecology 2009).

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Updated: 3/12/2014 12:00:00 AM