Abstract

Utah Lake, located in north-central Utah, USA, is a freshwater lake with a large surface area, shallow depth, and phosphorus-rich sediment with significant water-sediment interaction. These factors cause unique phosphorus behavior relative to other lake ecosystems, governed by sediment-water interactions. We hypothesize that benthic sediments and suspended solids act, by sorption processes, to maintain water column P concentrations that are largely insensitive to P inflows. We conducted a Phosphorus Addition Experiment to characterize sorbed P fluxes in the lake. Our experimental procedure included bench-scale laboratory experiments testing Utah Lake water and sediment with dilute and augmented P levels, as well as in situ field experiments in large mesocosms with augmented P. We analyzed field data collected when spring runoff diluted in-lake P concentrations to observe dilution response in situ. We assumed that P present in a filtered water sample consisted of dissolved P, and that the P present in an unfiltered sample included sorbed, colloidal, biomass-associated, and particulate P as well as dissolved P. We found that filtered water concentrations returned to a common dissolved water column P concentration of approximately 0.01-0.03 mg/L after augmentation or depletion of initial P concentrations. Our experiments demonstrated that water column P concentrations in Utah Lake are relatively insensitive to external P loadings. Rather, strong sorption and precipitation processes maintain relatively constant dissolved water column P concentrations and compensate for changes in nutrient loads and lake volume. Our conclusions inform discourse regarding implementing phosphorus-input-limiting strategies in the restoration of the Utah Lake ecosystem.

Degree

College and Department

Ira A. Fulton College of Engineering; Civil and Environmental Engineering

Rights

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