Paleoecological interpretation of the diatom succession in the recent sediments of Utah Lake, Utah

A diatom flora preserved in 250 sample levels of a 5 meter sediment core from Utah Lake, Utah, was found to be composed of 155 taxa. Dominance at different sample levels shifted among Melosirea granulata (Ehr.) Ralfs, Cyclotella meneghiniana Kutz., Diploneis smithii (Breb.) Cl., Amphora ovalis var. pediculus (Kutz.) V. H., Fragilaria construens var. venter (Ehr.) Grun., Stephanodiscus niagarae Ehr., and Fragilaria construens (Ehr.) Grun. Techriiques are described for both the successful diatom extraction from the core, as well as preparation and mounting of permanent slides using Hyrax as a mounting medium. Previously published geochemical analyses of the core, using atomic absorption spectrophotometry to determine concentrations of Ca, Fe, P, Na, and Al, are used to correlate past lake conditions with diatom frequencies. By the use of known lake phenomena and geo­chemical data, time lines were assigned to the upper part of the core. The settlement of Utah Valley in the year 1849 is thought to have occurred at about the 300 cm depth in the core. The consistently heavy draw-down and fluctuation of lake level following the year 1910 is thought to have contributed to the dominance of carp (Cyprinus carpio Linn.) and consequent heavy amounts of sus­pended materials present in the lake. The presence of quartz sand at about the 470 cm level of the core is presumably due to the formation of a shoreline established during an exceedingly low level of the lake more than 210 years ago. The current interpretation of the available data is that the lake has progressed from a deep-water mesotrophic lake to a shallow-water eutrophic body of water.