It appears the push to keep Lake Tahoe blue is working.
In the last five months of 2022, the beloved alpine lake on the California-Nevada border was the clearest it's been since the 1980s, the UC Davis Tahoe Environmental Research Center (TERC) reported Monday.
TERC credited a native zooplankton resurgence for the lake's improved clarity. The zooplankton act as a natural cleanup squad, helping to enhance Tahoe's renowned blue water.
According to TERC, the lake's average annual water clarity in 2022 was 71.7 feet, compared to 61 feet the year prior. Between August and December 2022, average clarity depth improved to 80.6 feet.
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The improvement in the final months of 2022 coincided with the highest numbers of zooplankton Daphnia and Bosmina, TERC said.
"Daphnia and Bosmina largely disappeared from the lake after they were grazed down following the introduction of the Mysis shrimp in the 1960s," TERC Director Geoffrey Schladow said in a statement. "In late 2021, the Mysis population unexpectedly crashed, and it took 12 months for the Daphnia and Bosmina to build up their numbers and start their natural cleansing."
The ultimate goal is to restore lake clarity to the historic 97.4 foot mark.
Going forward, researchers expect water clarity to continue to improve in 2023.
"We expect the impact of Daphnia and Bosmina to grow over 2023, and clarity may return to 1970s levels—despite the expected large runoff from this year’s record snowpack," TERC official Brant Allen said in a statement. "These events support the hypothesis we put forward several years ago that the food web is a major factor in controlling lake clarity."
But the improvement could be short-lived as researchers expect the Mysis shrimp population to rebound. Clarity could diminish as the shrimp consume Daphnia and Bosmina.
"Future management actions should explicitly look at incorporating ways of controlling the Mysis population," Schladow stated. "We have a brief window of time to monitor the lake in the absence of Mysis and then track the impacts of their return on lake clarity."
Click here to view TERC's entire Lake Tahoe water clarity report.
