Toxic algae mats – Stay safe this summer

As the summer continues and days get hotter, water in lakes and streams warms, potentially triggering algae blooms. While algae is an integral part of all water ecosystems, some algae blooms, especially those with cyanobacteria species mixed in, can present a danger to humans and pets.

“Both algae and cyanobacteria are natural parts of the ecosystem. They produce oxygen and are a food source,” explained Meghan Sullivan, from California Department of Parks and Recreation. But in the right conditions with nitrogen and phosphorus, warm water and lower water flows, algae and cyanobacteria can grow rapidly.

It can be difficult to visually determine if a toxin producing species is present in a mat, noted Sullivan. Early in the year, snow melt typically keeps the water temperatures low and flows high, discouraging rapid growth for blooms. Later in August and September, as flows drop, water warms, and more sunlight hits the channels, it can create perfect conditions for big algae and cyanobacteria blooms. As cyanobacteria blooms and decays, it can release toxins which cause health problems, especially for children and dogs due to their smaller body mass. Because these are cyanotoxins, treating the water by boiling it or using direct filtration does not remove toxins from the water.

Algae mats containing cyanobacteria may be on the bottom or detach and float on the water’s surface which allows them to move around with wind and currents, according to the State Water Resources Control Board (SWRCB). Sometimes the harmful algal blooms are easily visible, forming a “scum” or discoloration on the water surface. Other times, it is less visible, floating beneath the surface or attached at the bottom of a water body. To reduce risks of potential toxins, avoid the mats and scummy water.

“If the water is scummy and very green, don’t go in it,” said Sullivan. “Dogs should be on a leash when in a State Park anyway, and it helps to keep them from eating, drinking, or jumping into the water where the algae blooms are.”

Cyanobacteria occurs throughout the North Fork of the American River, Folsom Lake, and Lake Natoma, but biologists have identified areas with consistent populations of cyanobacteria creating potentially harmful algal blooms at Oregon Bar, Ponderosa Bridge, Mineral Bar, and Shirttail Creek near Yankee Jims.

SWRCB recommends taking key safety precautions when recreating near water that may have cyanobacteria: prevent children from playing with or handling algae mats; prevent pets from drinking water or eating scum, foam or algae; avoid swimming in areas of algae mats or scummy water; wash the family and pets off with clean water and prevent dogs from licking themselves until they are washed; and when fishing, throw away the guts and then clean fillets with tap or bottled water before eating.

Signs of toxic algae exposure include: sore throat or congestion; coughing, wheezing, or difficulty breathing; red, or itchy skin, or a rash; skin blisters or hives; earache or irritated eyes; diarrhea or vomiting; headache and abdominal pain. People should consult their physician if they believe their symptoms are from toxic algae exposures.

Pets may show similar symptoms to humans but also tremors and seizures, loss of energy and appetite, stumbling and skin irritation.  Consult a veterinarian if a pet shows signs of exposure. More information can be found at https://mywaterquality.ca.gov/habs/