Eutrophication of surface waters--Lake Tahoe

A survey was made of nutrient and other chemical constituents of surface waters from developed and undeveloped land areas, sewage effluents, seepage from septic tank percolation system and refuse fills, drainage from swamps, precipitation, and Lake Tahoe water. Algal growth stimulating potential of the samples were bioassayed with Selenastrum gracile as a test organism. Algal response to nutrients was measured by maximum growth rate and maximum cell count in a 5-day growth period. Ponds simulating the shallow portions of the lake were used for continuous flow assay of the biomass of indigenous lake organisms produced by sewage effluent. Flask assays and chemical analyses were made over two years on three major creeks. Twenty-eight other creeks and precipitations were monitored by chemical analysis. Evaluating the eutrophication potential, Lake Tahoe is nitrogen sensitive and responds to it in proportion to its concentration.