Doyle W. Stephens’s research while affiliated with United States Geological Survey and other places

Great Salt Lake (Utah, USA) is one of the world's largest hypersaline lakes, supporting many of the western U.S.'s migratory waterbirds. This unique ecosystem is threatened, but it and other large hypersaline lakes are not well understood. The ecosystem consists of two weakly linked food webs: one phytoplankton-based, the other organic particle/benthic algae-based. Seventeen years of data on the phytoplankton-based food web are presented: abundances of nutrients (N and P), phytoplankton (Chlorophyta, Bacillariophyta, Cyanophyta), brine shrimp (Artemia franciscana), corixids (Trichocorixa verticalis), and Eared Grebes (Podiceps nigricollis). Abundances of less common species, as well as brine fly larvae (Ephydra cinerea and hians) from the organic particle/benthic algae-based food web are also presented. Abiotic parameters were monitored: lake elevation, temperature, salinity, PAR, light penetration, and DO. We use these data to test hypotheses about the phytoplankton-based food web and its weak linkage with the organic particle/benthic algae-based food web via structural equation modeling. Counter to common perceptions, the phytoplankton-based food web is not limited by high salinity, but principally through phytoplankton production, which is limited by N and grazing by brine shrimp. Annual N abundance is highly variable and depends on lake volume, complex mixing given thermo-and chemo-clines, and recycling by brine shrimp. Brine shrimp are food-limited, and predation by corixids and Eared Grebes does not depress their numbers. Eared Grebe numbers appear to be limited by brine shrimp abundance. Finally, there is little interaction of brine fly larvae with brine shrimp through competition, or with corixids or grebes through predation, indicating that the lake's two food webs are weakly connected. Results are used to examine some general concepts regarding food web structure and dynamics, as well as the lake's future given expected anthropogenic impacts.

Hydrologic, sediment, and biological data were collected in the middle Green River basin in eastern Utah from 1991 to 2000 in an effort to monitor the effects of irrigation drainage on wetland areas and streams, aid in the development of remediation plans, and evaluate the effectiveness of selenium remediation efforts at Stewart Lake Waterfowl Management Area (WMA). Data consist primarily of selenium concentrations in surface water, ground water, bottom sediment, and biological samples. Supporting hydrologic data include field measurements of temperature, pH, specific conductance, water levels in wells, and discharge at surface-water sites. Selected water samples also were analyzed for major ions, trace elements, nutrients, and gross alpha and beta radiation. The concentration of selected selenium species is reported for several bottom-sediment samples from Stewart Lake WMA and the concentration of total selenium in suspended-sediment samples from the area are included. Well logs for six wells installed at Stewart Lake WMA are presented along with trace-element data for several biological samples collected at selected sites throughout the middle Green River basin.