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Nitrogen Fixation in Lakes: Response to Micronutrients and Exploration of a Novel Method of Measurement

Schmidt, Bethany Marie, Ms.
http://rave.ohiolink.edu/etdc/view?acc_num=kent1524172083482442

Abstract Details

2018, MS, Kent State University, 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 fixation is the acetylene reduction assay (ARA) using gas chromatography (GC). I examined a novel assay directly measuring dinitrogen gas using membrane inlet mass spectrometry (MIMS). The ARA method, although well established, has a long run time and does not directly measure dinitrogen. The MIMS assay has a much faster run time and measures nitrogen directly. However, the detection limit of the MIMS nitrogen fixation assay is unknown. To compare the detection limit of these two methods, an experiment was designed using a dilution series of a culture of the nitrogen fixing cyanobacteria Anabaena sp. While the ARA method was able to detect nitrogen fixation in all treatments, the assay using MIMS was only able to detect nitrogen fixation in the two treatments with the highest Anabaena sp. densities. Although the assay using MIMS is appealing in its quick run time and direct approach, the limit in its detectability of low nitrogen fixation rates may make it less favorable than the ARA method.
Darren Bade, Dr. (Advisor)
Mark Kershner, Dr. (Committee Member)
David Costello, Dr. (Committee Member)
82 p.
Ecology
Cyanobacteria; Nitrogen Fixation; Macronutrient and Micronutrient Limitation; Acetylene Reduction Assay; Membrane Inlet Mass Spectrometry; Method Comparison

Recommended Citations

Citations

  • Schmidt, B. M. (2018). Nitrogen Fixation in Lakes: Response to Micronutrients and Exploration of a Novel Method of Measurement [Master's thesis, Kent State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=kent1524172083482442

    APA Style (7th edition)

  • Schmidt, Bethany. Nitrogen Fixation in Lakes: Response to Micronutrients and Exploration of a Novel Method of Measurement. 2018. Kent State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=kent1524172083482442.

    MLA Style (8th edition)

  • Schmidt, Bethany. "Nitrogen Fixation in Lakes: Response to Micronutrients and Exploration of a Novel Method of Measurement." Master's thesis, Kent State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=kent1524172083482442

    Chicago Manual of Style (17th edition)

kent1524172083482442
424
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This open access ETD is published by Kent State University and OhioLINK.