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The elevation of Great Salt Lake has fallen to historic lows in recent years, exposing once submerged microbialites along the lake’s shores. Although prior studies have attempted to map microbialite locations, this has proved challenging, with mapped microbialite areas limited to accessible shoreline locations or via indirect sonographic evidence. Meanwhile, the importance of Great Salt Lake’s microbialites to the lake’s food chain has made quantifying the extent of microbialites exposed versus submerged at different lake elevations critical to lake management decisions. Low lake levels combined with seasonal high-water clarity have enabled microbialite reefs to be spotted in aerial and satellite imagery, even in deeper areas of the lake. In this study, satellite images were used to identify and map microbialite reef areas in Great Salt Lake and along its dry shores. In the south arm, submerged microbialites were easily recognized as dark green reefs against a light-colored benthic background (primarily ooid sand). Stationary microbialite mounds were distinguished from rip-up clasts or other dark-colored mobile material by comparing potential microbialite regions across several high-visibility timepoints. In this way, we identified 649 km2 (251 mi2) of putative microbialite reef area: 288 km2 (111 mi2) in the north arm, 360 km2 (139 mi2) in the south arm, of which 375 km2 (145 mi2) was mapped at a high degree of confidence. We also produced geospatial shapefiles of these areas. This map, combined with currently available lake bathymetric data, permits the estimation of the extent of microbialite reef exposed vs. submerged in various parts of the lake at different lake elevations. At the end of fall 2022, when lake level dipped to 1276.7 masl (4188.5 ft-asl) in elevation, we estimate that ~40% of the south arm microbialite reef area was exposed. 

Great Salt Lake hosts an ecosystem that is critical to migratory birds and international aquaculture, yet it is currently threatened by falling lake elevation and high lakewater salinity resulting from water diversions in the upstream watershed and the enduring megadrought in the western United States. Microbialite reefs underpin the ecosystem, hosting a surface microbial community that is estimated to contribute 30% of the lake’s primary productivity. We monitored exposure, desiccation, and bleaching over time in an area of microbialite reef. During this period, lake elevation fell by 1.8 m, and salinity increased from 11.0% to 19.5% in open-water portions of the outer reef, reaching halite saturation in hydrologically closed regions. When exposed, microbialite bleaching was rapid. Bleached microbialites are not necessarily dead, however, with communities and chlorophyll persisting beneath microbialite surfaces for several months of exposure and desiccation. However, superficial losses in the mat community resulted in enhanced microbialite weathering. In microbialite recovery experiments with bleached microbialite pieces, partial community recovery was rapid at salinities ≤ 17%. 16S and 18S rRNA gene sequencing indicated that recovery was driven by initial seeding from lakewater. At higher salinity levels, eventual accumulation of chlorophyll may reflect accumulation and preservation of lake material in halite crusts vs. true recovery. Our results indicate that increased water input should be prioritized in order to return the lake to an elevation that submerges microbialite reefs and lowers salinity levels. Without quick action to reverse diversions in the watershed, loss of pelagic microbial community members due to sustained high salinity could prevent the recovery of the ecosystem-critical microbialite surface communities in Great Salt Lake. 

The Geoscience Education Targeting Underrepresented Populations program is a National Science Foundation funded project designed to assess the effectiveness of a multifaceted approach to increase recruitment and retention in Earth & Environmental Science (EES) majors at Weber State University (WSU) in Ogden, Utah. This program integrates a combination of early outreach to high schools, concurrent-enrollment courses, a summer bridge program, structured early undergraduate research experiences, community engaged learning, and multiple pedagogies to support a diverse student population. The focus of this presentation will be on the place-based educational approach to teaching an Earth science summer bridge program and a first-year summer research experience. These programs overlap in both time and location allowing incoming students to have peer-to-peer interactions with current EES majors. The summer bridge program runs for two weeks and provides students with an introduction to the WSU campus, available student services, initial advising, and an early collaborative research experience focused on local natural hazards and the Great Salt Lake basin water resources. Students collect water samples from Great Salt Lake, local streams, and a groundwater well field on WSU’s campus. Students then analyze major element chemistry of those samples with the help of faculty and students in the EES department using lab facilities at WSU. The summer research program is a four-week summer program for freshmen and sophomores who have declared an EES major. Students conduct in-depth field and lab research project on the Great Salt Lake ecosystem, using real-time geochemical data collected from field observatories on Antelope Island State Park. Students work as a team with a faculty lead and senior peer teaching assistants to address a research question by analyzing field station data as well as collecting and analyzing environmental chemistry and microbiology samples from the lake, including alkalinity, inorganic and organic carbon, major ions, cell counts, and photosynthetic efficiency. The summer research students also act as peer mentors for students in the Summer Bridge. All students present their research finding to friends and family at a celebratory event on the last day of both programs. We will present on the successes and challenges of the program to date and our plans to assess various components and their overall impact on student recruitment and retention in our department.