As summer temperatures intensify, vivid streaks begin appearing in Clark County’s lakes and rivers.
The culprit is cyanobacteria, a microscopic aquatic and photosynthetic bacteria, otherwise known as blue-green algae, said Lizbeth Seebacher, who oversees the state Department of Ecology’s algae control and invasive aquatic species programs.
Cyanobacteria can cause rashes, abdominal pain, diarrhea, respiratory illness, seizures — and even death.
Despite this name, cyanobacteria aren’t true algae, or eukaryotes, but instead relatives of bacteria. Like true algae, however, they contain chloroplasts that turn light into energy. The bacteria colonies often look the same as nontoxic green algae.
Cyanobacteria grow naturally in all water body types, salty or fresh. In Clark County, harmful blooms typically appear in Vancouver, Lacamas and Round lakes, said James Morrill, Clark County Public Health environmental health specialist.
Did you know?
Cyanobacteria, microscopic bacteria forming harmful algae blooms, are some of the oldest known organisms on Earth. They date back 3.5 billion years, making them nearly as old as some of the planet’s oldest rocks, which are roughly 4 billion years old.
The blooms vary in color — blue, green, gold and reddish-brown. The scum can look slimy, foamy or clumpy.
Harmful cyanobacteria blooms occur when the weather warms up, typically in late summer and fall. But in the past few years, the region has experienced hot weather as early as spring.
In addition, the growing human population and agricultural activity can create excess nutrients that flow into nearby bodies of water. These “nutrients” aren’t the good kind, but uncontrolled runoff of fertilizers and leaks from septic systems. Even washing cars where the soapy water can reach lakes and rivers can feed cyanobacteria.
When property owners remove aquatic vegetation that consume nutrients, such as phosphorus and nitrogen, more are available to feed the harmful blooms.
Cyanobacteria produce liver and neurotoxins that are harmful to both humans and animals, including fish species. Exposure can be as minimal as splashing or swimming in contaminated lakes and rivers, or it can be as direct as consuming contaminated fish or water.
Blooms can also deplete oxygen in water, which can suffocate fish and other aquatic life.
Pierce and Thurston counties have the highest number of reported harmful blooms in the state, Seebacher said.
In 2021, dogs across Washington became severely sick or died from contact with harmful algae blooms, including in the Columbia River in Southwest Washington, she said.
Laboratory testing is the only way to tell if a bloom is toxic. Clark County Public Health monitors the county’s designated swim beaches between Memorial Day and Labor Day and lists test results at www.clark.wa.gov/public-health/public-beaches. It posts warnings at water bodies where toxins are detected. Test results from rivers and lakes statewide are on the Washington State Toxic Algae website, www.nwtoxicalgae.org.
Morrill’s advice for swimmers, boaters and paddleboarders: “When in doubt, stay out.”
