Songlin Cheng (Committee Co-chair), David Dominic (Committee Member), Rebecca Teed (Committee Co-chair)
Master of Science (MS)
Crystal Lakes are a group of four interconnected lakes, located in southwestern Clark County, Ohio. Several studies have looked at separate geochemical and isotopic information at this location. However, no one has thoroughly studied the relationship between the algal community, geochemistry, and carbon isotope fractionation within Crystal Lake. The fractionation of carbon isotopes of dissolved inorganic carbonate is greatly affected by the process of photosynthesis; the amount of photosynthesis is affected by the amount of algae in the aquatic community; the amount of algae is affected by the available nutrients in system. Therefore, there should be a correlation between the nutrients in the water column, the amount of algae, and the extent of carbon isotope fractionation. If such a correlation is found, it could be used as a proxy for paleonutrient availability. To determine this correlation, water samples were collected via submersible pump every 1.5 meters at approximately the deepest location in Crystal Lake. Several parameters that are important indicators of photosynthesis, such as dissolved oxygen and pH, were measured in situ. The collected samples were analyzed for nutrient and chlorophyll content; samples were also sent out for carbon isotope analysis. The measured values of δ13C in Crystal Lake are highest in areas of photosynthesis, and decrease in the hypolimnion where decomposition of accumulated biomass occurs. There is a clear trend between carbon isotope fractionation and photosynthetic indicators, such as dissolved oxygen and pH. Trends between several nutrient concentrations and fractionation was also observed. Samples with δ13C values less than -10 per mille V-PDB have pH values below 8 and little dissolved oxygen (0-1 mg/L). Samples with δ13C values between -9 and -6 per mille V-PDB have pH values greater than 8, dissolved oxygen levels between 5-20 mg/L, silica concentrations below 3.25 mg/L, magnesium concentrations below 27 ppm, and calcium concentrations above 60 mg/L. Samples with δ13C values above -6 per mille V-PDB have a pH between 8-9, dissolved oxygen levels between 10-30 mg/L, silica concentrations above 3.25 mg/L, magnesium concentrations above 27 ppm, and calcium concentrations below 60 mg/L. More research is needed to corroborate these trends and expand our understanding of the affect of nutrient concentrations on carbon isotope fractionation.
Department or Program
Department of Earth and Environmental Sciences
Year Degree Awarded
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