Publication Date
2024
Document Type
Thesis
Committee Members
Stephen J. Jacquemin, Ph.D. (Committee Chair); Silvia E. Newell, Ph.D. (Committee Co-Chair); Katie Hossler, Ph.D. (Committee Member)
Degree Name
Master of Science (MS)
Abstract
Excess anthropogenic nitrogen (N), primarily from agricultural field fertilization, causes nutrient runoff that stimulates harmful algal blooms (HABs) in western Lake Erie. As a critical tributary to Lake Erie, nutrient loading from the Maumee River drives the intensity of the annual summer HABs in the western basin. Knowledge gaps around rates of N transformations in the Maumee River currently hinder the calibration of in-river parameters in Soil and Water Assessment Tool (SWAT) models for the Maumee watershed. To address these gaps, this research quantified rates of ammonium uptake, ammonium remineralization, nitrification, and bacterial respiration alongside physicochemical parameters of the river. Monthly sampling was conducted along the Maumee River at International Park (river mile 4.53), Mary Jane Thurston (river mile 31.88), and Independence Dam (river mile 59.31) over the course of a year. Ammonium uptake rates ranged from 1.2 to 8.7 µmol N L-1 hr-1 for water samples incubated under light conditions and from 0.2 to 1.9 µmol N L-1 hr-1 under dark conditions, while ammonium regeneration ranged from <0.01 to 12.0 µmol O2 L-1 hr-1. Bacterial respiration rates averaged 525.0 ± 28.5 µM O2. Respiration and both NH₄⁺ uptake & regeneration rates correlated overall with seasonal temperatures and biomass. Respiration rates closely followed temperature, with warmer months having the highest rates. November 2022 samples exhibited higher rates of respiration and both NH₄⁺ uptake & regeneration at all sites as chlorophyll was >200 µg/L during the fall river bloom. Despite not being at peak temperature in the study, the highest rates of microbial activity in April and May., with the lowest observed during the coldest months, January and March. The timing of peak rates at the three sites along the river-to-lake continuum shifted with biomass, indicating the importance of parameterizing the SWAT model with models with spatially and temporally dynamic values. These findings will help refine the SWAT model to account for seasonal variations within the Maumee River, thereby informing more effective nutrient management strategies to protect the ecological health of Lake Erie.
Page Count
96
Department or Program
Department of Biological Sciences
Year Degree Awarded
2024
Copyright
Copyright 2024, all rights reserved. My ETD will be available under the "Fair Use" terms of copyright law.
