The eutrophication potential of Lake Mead, with primary emphasis on Las Vegas Bay, was determined with Selenastrum capricornutum. Nutrient limitation profiles were determined for three sampling stations in Las Vegas Bay and one in Boulder Basin. After heavy metals were chelated with EDTA, P was identified as the primary limiting nutrient with N the secondary limiting nutrient for S. capricornutum. Productivity potential was highest in upper Las Vegas Bay near the sewage inflow. Toward the mouth of the bay and in Boulder Basin, progressively lower potentials were defined. Productivity potential could not be predicted from the filtered samples because the nutrients bound up in the indigenous biomass remained on the filters. Autoclaving followed by filtration prior to assay enabled S. capricornutum to produce yields relative to the productivity observed in the lake.