Aquatic Sciences Meeting, Albuquerque 2001

PC11 Human Activities and Aquatic Ecosystems

Date: Thursday, February 15, 2001

Location: Southwest Hall

Liu, M, S, University of California at Davis, Davis, USA, msliu@ucdavis.edu

Reuter, J, E, Univeristy of California at Davis, Davis, USA, jereuter@ucdavis.edu

Goldman, C, R, University of California at Davis, Davis, USA, crgoldman@ucdavis.edu

SEASONAL SIGNIFICANCE OF ATMOSPHERIC DEPOSITION OF PHOSPHORUS AND THE SOURCES OF DEPOSITION FOR LAKE TAHOE, CA-NV

Increases in nutrient inputs, especially phosphorus, into Lake Tahoe are contributing to the rapid decrease of the Lake’s famous clarity. Atmospheric deposition is estimated to be responsible for 20-30% of the annual external phosphorus inputs into Lake Tahoe. Seasonally, atmospheric fallout is more significant because the deposition of phosphorus can increase during the dry months when stream flows are very low. This phosphorus source also falls directly on the water surface into the photic zone, increasing its availability to algae. Bulk deposition measurements along Lake Tahoe’s north shore were collected from July through September 2000. Preliminary analysis reveals that during this period, atmospheric deposition (predominantly dry) provided several times more phosphorus than streams. Approximately 50% of the total phosphorus was immediately biologically available. The phosphorus collected this summer may be slightly higher than long-term deposition data at Ward Creek, possibly due to collection differences. Future analysis of this summer’s samples by electron microscopy will give clues to the sources of fallout materials and their relative importance. Road dust and wind-blown soil are predicted to be major summer sources.

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Aquatic Sciences Meeting, Albuquerque 2001

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