Lakes close because of toxic algae every year, especially as temperatures climb in summer.
Pierce County’s Lake Tapps is the latest example. Authorities warned people not to swim in the northeast part of the lake last week.
In King County, caution signs remain up at Mallard Lake in White Center, where a sample showed toxicity at levels higher than the state’s guidelines advise on July 10.
Warmth, light and nutrients from runoff can cause growths of so-called cyanobacteria to flourish. It appears as blue-green scum in or on the water and can make people and animals sick if ingested. It has killed dogs in recent years.
Debra Bouchard, with King County’s Water and Land Resources Division, says the first thing to know is to stay out of the water if you see any kind of scum in it. She says they’ve seen toxic blooms that are smaller than a silver dollar.
"And kind of clumps along the water. Sometimes, depending on if it’s been windy and the water’s been turned up, it can look like green flecks distributed throughout the water column. Or if the water’s really still and it’s a smaller, shallower lake, it can look like somebody spilled paint along the top surface of the water,” Bouchard said.
The state Department of Ecology has a website where people can report blooms they see and think might be toxic. A lab in King County will test samples sent in by the public if there’s sufficient concern of a health risk
Lizbeth Seebacher, with the state Washington State Department of Ecology’s freshwater algae control program, says it’s best to reach out first by email or phone. In past years, the program has run out of funds before the end of the algae season.
“For example, 2015, our drought year that was very, very warm. That was our worst year so far, with regard to blooms. So there were something like 470 samples sent in that year,” Seebacher said.
The website to check for closures and information on reporting is www.nwtoxicalgae.org. Once confirmed, local authorities can post signs to warn of the risk or close affected beaches.