Primary productivity is a measure of the rate at which solar energy is converted into chemical energy by photosynthetic organisms. Phytoplankton is used to assess primary productivity in Lake Tahoe. At low levels, primary productivity can become a limiting factor in the population size of organisms that depend directly or indirectly on this source of food. Conversely, extremely high primary productivity can result in nuisance algal blooms, degradation of drinking water taste and odor, low dissolved oxygen, and fish kills. It is suspected that activities associated with urbanization and watershed disturbance influence Lake Tahoe’s primary productivity through the release of nutrients and subsequent transport in runoff, or through the atmospheric deposition of nutrients. Drivers influencing the delivery of fine sediment and nutrients include urban development, anthropogenic and natural disturbance in the undeveloped portions of the watershed and local and regional climate. Many programs throughout the Tahoe Basin are aimed at reducing nutrient inputs into Lake Tahoe such as stormwater reduction and stream restoration projects. Primary productivity has been measured at Lake Tahoe by UC Davis since 1968. 

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