LAKE COUNTY ? A 15-year study of the mercury levels in Clear Lake and the effects on the lake”s ecosystem made its official debut Tuesday.
The University of California, Davis study, titled “Mercury Cycling and Bioaccumulation” in Clear Lake, appeared in Ecological Applications, a publication of the Ecological Society of America. United States Geological Survey Lead Scientist Tom Suchanek, who co-authored the study, presented it to the Lake County Board of Supervisors Tuesday morning, and then held a reception at the Lake County Museum.
The study began in 1992. It details mercury levels in Clear Lake during a 3,000-year period and compares them to levels surrounding mercury mining at the Sulfur Bank Mine. Suchanek said it was the first study of the effects of a mercury mine on a lake and its ecosystem, specifically having to do with the production of methylmercury.
Suchanek said methylmercury, as opposed to elemental mercury, is dangerous to humans and animals, and accumulates in the muscle tissues of fish.
“In comparison with all sites around the world and with lakes all over the world, Clear Lake, even though it has higher concentrations of mercury in the water ? total mercury in the water ? the methylmercury is much lower,” Suchanek said.
Methylmercury is produced when elemental mercury interacts with bacteria in the lake”s sediment. Suchanek said one of the reasons there is less of the toxic material in Clear Lake is that the mercury that leeches into Clear Lake from the mine is bonded with sulfur, making it difficult for bacteria to break down.
Other reasons include Clear Lake”s shallowness and resulting warmth, according to Suchanek. He said methylmercury production is prolific in cold, low-oxygen layers that form at the bottoms of lakes that are 50 feet deep or more.
“During the time that we were working, there were some indications that people wanted to dredge the lake to make it a better habitat for trout or other kinds of fish. We believe that would be a real mistake,” Suchanek said.
Methylmercury accumulates in plankton, insects and fish, and is becomes more concentrated the higher it gets in the food chain. Suchanek said the highest accumulations were found in largemouth bass, which are at the top of the lake”s food chain, found in the Clearlake Oaks arm of the lake.
The study can be downloaded free of charge at www.esajournals.org/toc/ecap/18/sp8.
Contact Tiffany Revelle at trevelle@record-bee.com, or call her directly at 263-5636, ext. 37.
