Clear Lake Gets New Treatment to Stop Toxic Algae Blooms

For decades, Clear Lake in Northern California has faced a painful irony. It holds more fish per acre than any other lake in America, yet toxic algae blooms poison its waters every summer, making people and animals sick and shutting down recreation.

Now, scientists believe they've cracked the code to restore the lake's water quality.

On April 16, 2026, researchers tested a promising new treatment across 400 acres of the lake. They applied EutroSORB G, a clay-like material made from lanthanum-modified bentonite, designed to sink to the lake bottom and trap excess phosphorus in the sediment. Phosphorus is the main nutrient that fuels the harmful cyanobacteria blooms that have plagued the lake for years.

Dr. Alexis Fischer, a water quality specialist at EutroPHIX, led the team in mapping 66 sites across the lake to find where phosphorus concentrations ran highest. The material binds to phosphorus and prevents it from re-entering the water where it feeds the toxic algae.

"If the results are successful, they would support a larger future project at a scale that would be more appropriate for improving lake-wide water quality," Fischer explained. The team will return in three months to measure effectiveness, then again in one year.

The Ripple Effect

The stakes go far beyond water quality. Lake County depends on Clear Lake as its main source of drinking water and a cornerstone of local tourism. Every summer when algae blooms take over, beaches close and visitors stay away, hitting the local economy hard.

District 4 Supervisor Brad Rasmussen, who serves on the state's Blue Ribbon Committee for the Rehabilitation of Clear Lake, sees this as a turning point. "It is the oldest lake in North America," he said. "The county is committed to keeping that a top priority. It is a huge piece of our economic viability."

The phosphorus problem stems largely from agricultural runoff and the loss of over 90% of the lake's natural wetlands. Levees built decades ago cut off marshlands that once filtered nutrients before they reached the water. Jim Steele, a longtime ecologist who has studied the lake for decades, notes that research dating back to the 1990s identified phosphorus as the main culprit.

The initial demonstration cost $3 million in state funding. Treating the entire lake could run $200 million over 10 to 20 years, but even targeting the worst areas could make a dramatic difference for tens of millions.

Scientists and local officials gathered at the lake's edge in Lucerne to witness the treatment, a moment of hope after years of watching their beloved lake struggle. The lake that once thrived could thrive again.