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(continued from previous) Limnological characteristics of Lake of the Ozarks, Missouri II: Measurements following formation of a large reservoir upstream. 1988. J.R. Jones and M.S. Kaiser. The main objective of this study was to determine if water quality in LOTO changed after the completion of Truman Reservoir. The hypothesis was that Truman Reservoir would act as a settling basin, decreasing the amount of inorganic suspended sediment entering LOTO. Lower turbidity would allow more light to penetrate into the water column and lead to more algal growth, especially up-lake. Data were collected during the summers of 1980-1986, with samples coming from the six previously monitored sites as well as two additional main lake sites (18- and 28-mile markers). Data showed that shifts in water quality were minimal and the strong longitudinal gradient in the main lake was still present during 1980-1986. Because inorganic suspended sediment measurements were limited to only one summer prior to the completion of Truman Dam, changes in suspended sediment concentrations could not be quantified. Monitoring of surface water near the dam on Truman Reservoir revealed lower phosphorus and inorganic suspended sediment values than measured at the up-lake LOTO site. As expected, Truman Reservoir was acting as a settling basin with outflows containing moderate levels of nutrients and suspended sediment. It was theorized that releases from Truman Reservoir scour the Osage River bed, increasing the phosphorus and inorganic suspended sediment concentrations in water moving down-lake.
When water quality data were adjusted to account for differences in seasonal inflow, sites across the lake were determined to have higher chlorophyll concentrations (about 25% higher), even though phosphorus levels had dropped by about 26%. Secchi transparency values across the lake remained relatively unchanged after the completion of Truman Reservoir. Along with potential shifts in the algal community, lower inorganic suspended sediment concentrations in LOTO may account for increased algal production. In Missouri, both inorganic suspended sediment levels and algal biomass determine Secchi transparency. Because algal chlorophyll concentrations increased across the lake during 1980-1986 while Secchi measurements remained unchanged, it seems reasonable to surmise that inorganic suspended sediment levels decreased. In essence, the increased clarity associated with decreased inorganic suspended sediment was countered by increased algal biomass, which was made possible by the more favorable light environment that resulted from lower inorganic suspended sediment levels.
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