MS, Kent State University, 2018, College of Arts and Sciences / Department of Biological Sciences

Chapter 2 Abstract: Anthropogenic changes in the availability of nutrients in freshwater systems can affect the growth and composition of the cyanobacterial community through changes in biological processes. Limitations on these biological processes are used to develop management plans for reoccurring algal blooms. Nitrogen fixation is a biological process that converts inert dinitrogen gas into biologically available ammonium. In freshwater systems, certain cyanobacteria possess this ability to fix nitrogen, giving them an advantage under nitrogen-poor conditions. Nitrogen fixation and cyanobacterial growth could be limited by phosphorus, but pollution has often created situations where phosphorus is in excess. The process of nitrogen fixation is also dependent on the presence of multiple micronutrients, which are involved either as cofactors or in maintenance of cells. This dependence on micronutrients leads to the question of whether micronutrients could limit nitrogen fixation and cyanobacterial growth when phosphorus is abundant. To investigate the response of nitrogen fixation rates to micronutrient enrichment, I conducted macronutrient (phosphorus) and micronutrient (iron, boron, molybdenum) addition bioassays using water samples collected from 8 field sites in northern Ohio. In 5 of the 8 sites sampled, nitrogen fixation rates were significantly increased by additions of phosphorus. Micronutrient limitation was only observed in 1 of the 8 sites, with the molybdenum addition further increasing rates of nitrogen fixation. If micronutrient limitation on nitrogen fixation rates is absent or rare in northern Ohio, nitrogen fixation may serve as a hinderance in nitrogen control practices for the reduction of cyanobacteria growth within freshwater systems. Chapter 3 Abstract: The ability to detect low rates of nitrogen fixation in freshwater systems may differ depending on the method of analysis used. A traditional technique to measure aquatic nitrogen fixatio (open full item for complete abstract)

Committee: Darren Bade Dr. (Advisor); Mark Kershner Dr. (Committee Member); David Costello Dr. (Committee Member) Subjects: Ecology