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Show the redissolution of sodium chloride from the lake bed, particularly in the south arm. Notwithstanding slight fluctuations in relative ion ratios in lake water with changes in lake elevation, it is not believed that the overall chemistry of lake brines has changed greatly. It is believed that the lake model currently being verified and calibrated by USGS will provide answers related to the salt- load balance between the two main arms of the lake and change in salinity and chemistry. ( See Appendix H.) Accounting for Quantitieis and Locations of Salts The location and amount of salts in the open lake are determined through water sampling and modeling. ( See Appendix H.) Data on locations and amounts of salts elsewhere are less available. Given recent attention to the salt balance in the lake and emerging disputes over mineral ownership, DFFSL would like to know more about locations and quantities of salts in the system. This information also will be useful when considering potential recovery of the economic value of stockpiled and waste salt, and when planning for eventual reclamation. Nutrient Chemistry The biological productivity of the GSL is largely determined by the concentrations of plant nutrients in the water. Most often, nitrogen, phosphorous or combinations of these two nutrients control plant growth in freshwater lakes. Bioassay analyses of south- arm water of the lake have indicated that nitrogen concentrations most frequently control phytoplankton growth in the lake ( Stephens and Gillespie, 1976). Unlike the conservative major ions discussed previously, the concentrations of nutrients in the lake are more dynamic and controlled both by nutrient loading from tributaries and the atmosphere, as well as hydrological and biotic processes in the lake. Upon entering the lake, dissolved forms of nutrients that limit plant growth will readily be taken up by the phytoplankton passed through the food web and repeatedly recycled until organic matter sedimentation buries it in the lake bottom. Nutrients entering in particulate form may sediment out directly and not enter the lake's food web. Relatively little information is available about the flux of nutrients into the lake and the concentrations present in the water. Studies conducted by Sturm ( 1980) and Wurtsbaugh ( 1995) reported high total phosphorus. Sturm ( 1980) also reported exceedingly high nitrate concentrations while a Wurtsbaugh ( 1988) study indicated algal nitrogen limitation. This discrepancy may be due to problems with measuring nutrient concentrations in the GSL's brines and/ or different years when the measurements were made. Anthropogenic factors undoubtedly have a large influence on the concentrations and distribution of nutrients in GSL. When tributary waters pass through wetlands prior to entering the lake, substantial portions of the nutrients may be removed ( Home and Goldman, 1994). Because most of the GSL's wetlands have been created or enhanced by diking, this likely results in a substantial loss of nutrients to the lake. Conversely, domestic sewage effluents and agricultural wastes from the watershed are possibly increasing the nutrient 51 |