The assumption’s been thrown on its head with UC Davis scientist Shohei Watanabe conducting research in collaboration with researchers from NASA’s Jet Propulsion Laboratory and Canada’s Laval University. There were times when the lake was clearer, it was less blue and when lake was less clear, it was deep blue. During this period of clarity, the deep blue color of the lake will diminish. The blueness comes from the amount of algae in the water instead of clarity.
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Scientists reveal the reason why Lake Tahoe is blue, not because the water is clear, but because of the algal concentration, which determines the water color.
Until recently it was long believed that keeping the lake’s waters clear and clean is the best solution to preserve its unique blue shades.
When the results were combined with other measurements taken to determine the clarity of the lake, something surprising was discovered – blueness and clarity are not actually similar but vary opposite. The less nutrients, the less algae, and the bluer the lake.
“Blueness is one of the iconic values of Lake Tahoe and I think we were always assuming blueness equates to clarity”, Schladow said. Clarity is measured by observing the depth at which a dinner-plate-sized white disk remains visible when lowered into the water.
“Less nutrients washed into lake, nutrients that helped algae to grow”, Schladow says of the drought. The sediments that are gathered in the lake affects the overall clarity while the concentration of the algae affects the bluish color of the lake. This is also the time of the highest concentrations of clarity-robbing sediment particles, research suggests. Blueness is controlled by algal concentration, which in turn is controlled by the level of nutrients available to the algae.
Residents in Sierra Nevada, United States have always been particularly attached to their famous Lake Tahoe.
Or, benefits of the new research can be summed up more simply.
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“Though it’s really quite subjective, you can now put a number on blueness”, says Geoffrey Schladow, director of the UC Davis Tahoe Environmental Research Center, who worked with Watanabe on the study, in a phone interview.
