If you though Lake Tahoe gets its signature blue tint from the purity or the clarity of the water, think again. A team of researchers have just found that the shade is given by the low amount of algae that the water contains.
It’s a discovery that has taken the scientific community completely by surprise as no one expected to find this answer when they set out to investigate the matter.
Shohei Watanabe, a postdoctoral researcher and member of the University of California, was the researcher who came up with the idea of creating a “Blueness Index” that would help experts measure what are the factors that contribute to the lake’s specific blue tint. He proposed using data from one of NASA’s Jet Propulsion Labs as well as an instrument that’s good at capturing light.
Geoffrey Schladow, the UC Davis Tahoe Environmental Research Center’s director and one of Watanabe’s colleagues, gave a statement saying that “Though it’s really quite subjective, you can now put a number on blueness”.
Field experts have been fighting for decades for conservation efforts that were believed to help them restore the water’s former clarity and blueness. But the new study has shown that clarity and color have nothing to do with one another. What the researchers found is that the fewer algae the lake has, the bluer its color appear to be.
Watanabe stressed in his report that the findings don’t mean that the clarity of the lake should be dismissed and ignored, bur rather that the algae concentration as well as the nutrient input should be kept closely under control in order to really keep Lake Tahoe clear and blue.
The paper also informs that the clarity of the water is controlled by sediment, whereas the blueness of the water is controlled by the algal concentration. In turn, the algal concentration is determined by the amount of nutrients (phosphorus and nitrogen in particular) that the algae have available.
Since Lake Tahoe is bluer when its level of nutrients is low, it currently has the perfect conditions to hold on to its blue tint as drought in the area has greatly cut off the flow of water (which brings sediment and nutrients with it) that’s coming into the lake from various rivers and creeks.
Schladow explained that the fewer nutrients wash into the lake, the less algae will grow. He went on to add that Mother Nature has shown us all what happens when nutrients find their way into the lake, but Lake Tahoe has shown us all what it requires in order to stay clear and blue. And we should respect that.
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