Wildfire smoke, ash may leave lasting impact on Lake Tahoe

Published: Oct. 4, 2021 at 7:21 PM PDT
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RENO, Nev. (KOLO) - The Caldor Fire slipped by the southern end of the Tahoe Basin, largely missing the neighborhoods there, but it also filled the Basin with smoke for weeks. Then the ash from more distant fires took its place. The skies will clear eventually, but the ash will remain, much of it in the water.

Just what that will mean for Tahoe and other alpine lakes in the west isn’t known, but scientists, including a team from UNR are working to find out. They have an idea what they will be looking for. Dr. Facundo Scorco studied the effects of wildfire smoke at another lake in northern California in 2018.

“It changed completely the structure of the algae there and all the animals living in the lake.”

They will be looking for similar impacts at Tahoe. The key to the vulnerability of it’s legendary clarity has always been the growth of algae and that depends in surprising ways on sunlight. If smoke clouds the sky and falling ash the lake that would seem to retard the growth of algae. It’s not that simple. It turns out ultraviolet light keeps algae in check and when it’s blocked algae blooms.

“In a counterintuitive way you might actually stimulate production because the ultraviolet light isn’t suppressing the algae that’s growing in the waters,” says Sudeep Chandra, UNR Biology professor and co-chair of the Tahoe Science Advisory Council.

Of course, not all of the ash is falling from the smoke. It will also find its way to the lake with runoff from rain or snow melt, especially in the southern end of the lake.

“Around big precipitation events we’re going to see a lot of particle loadings into the lake,” says UNR’s Dr. David Hanigan. “Also dissolved chemicals will come out of this.”

“You might actually have cascading influences up the food web,” adds Chandra. “You might have things change the invertebrates that are feeding on the algae and supporting the fishery. Currently these are unknowns up at the lake. We don’t have much information that connects wildfire smoke or direct runoff to changes in the biology of the system and then maybe into the fishery.”

Those are answers waiting for all western lakes, but with Tahoe’s long history of research there may be no better time or place to find them.

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