LAKE COUNTY, Calif. – The summer’s high temperatures have contributed to an algal bloom that’s impacting Clear Lake, with recent testing of 30 sites on the lake finding concerning levels of cyanotoxin.
On Thursday, Lake County Water Resources reported on the lake-wide algae bloom.
“Due to the very warm weather and the extended light periods this time of year, the shallow waters of Clear Lake are a perfect environment to encourage growth of aquatic plants, planktonic algae (floating green algae) and cyanobacteria (blue-green algae),” the agency reported.
While officials said that much of what currently is seen on the lake is harmless, cyanobacteria – if it grows in enough abundance – can produce cyanotoxins, which can be a health hazard to humans, livestock and pets.
Water Resources said algae and cyanobacteria are naturally occurring in all water bodies on planet earth, explaining that the algae and cyanobacteria in Clear Lake can grow in large amounts using sunlight, warm air temperatures and food from nutrients like phosphorus and nitrogen).
“Phosphorous is the main nutrient driving these blooms, and the majority of phosphorus comes from the nutrient-rich bottom sediments of the lake,” Water Resources said in its report, adding that Clear Lake is very old and relatively shallow, and has accumulated a thick layer of sediments during its existence.
Water Resources said that Clear Lake is different from the young and vibrantly blue reservoirs in California such as Pillsbury, Folsom, Berryessa and Shasta because it can’t draw down its nutrient- and algae-rich water due to the restrictive Grigsby Riffle rock formation at the Cache Creek outflow.
As a result, every year the algae and phosphorus accumulate in the lake, settle into the sediments, and are ready to be used for next summer’s algae blooms. “This is an ongoing cycle,” Water Resources said.
Meantime, the Big Valley Band of Pomo Indians and Elem Indian Colony are continuing regular lake water monitoring at approximately 30 Clear Lake sites.
On Thursday, Lake County Public Health Officer Dr. Gary Pace said that the results from preliminary testing conducted on Tuesday found cyanotoxin at the “warning” level at nine sites: Elem Indian Colony shoreline, Austin Park in Clearlake, Keeling Park in Nice, Sulphur Bank Mercury Mine shoreline in Clearlake Oaks, Buckingham, Jago Bay, the CL-4 site located in the center of the lake’s Oaks arm, Lily Cove and Lucerne.
Pace said lab testing results will be available by early next week, and results will be made public.
Cyanobacteria can pose health risks, particularly to children and pets. As such, Pace urged boaters and recreational users to avoid direct contact with or use of waters containing cyanobacteria in Lake County.
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County officials report on lake-wide algal bloom, cyanotoxin testing results
- Elizabeth Larson
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