Has Lake Davis been polluted?

Some authorities say that the lake is not now, and never has been, polluted. Core samples going back many years, taken by the United States Department of Agriculture in conjunction with the University of California, Davis, prove that the cyanobacteria are natural parts of the food chain in the lake and the riparian zone which surrounds it. It is known that many Native American settlements were near the lake, and the native Pomo prized the lake for its large population of fish, which could not be supported without large quantities of algae.