Publication Date
2021
Document Type
Thesis
Committee Members
Chad R. Hammerschmidt, Ph.D. (Advisor); Silvia E. Newell, Ph.D. (Committee Member); Mark J. McCarthy, Ph.D. (Committee Member)
Degree Name
Master of Science (MS)
Abstract
Excess phosphorus (P) and nitrogen (N) in the western basin of Lake Erie drive annual cyanobacteria blooms and associated hypoxia events. The Maumee River inputs ~5% of the water load into the western basin and ~50% of annual P loadings. I quantified seasonal variability of net P and metals fluxes from sediments in the Maumee River at four stations from Defiance, Ohio, to Maumee Bay. Upriver sediments were, on average, a total and filtered P sink throughout the year (−19 ± 7 and −6 ± 3, respectively; all fluxes represent `net flux’ reported in µmol m−2 h−1). At the river mouth, sediments were a source for total P in April (+91 ± 18), then shifted to a total P sink from August through October (−8 ± 5). In Maumee Bay, sediments were a total P source in May and October (+21 ± 5) but a sink during intervening summer months (−2 ± 1). Maumee River sediments were a sink for total aluminum (−92 ± 63), iron (−80 ± 35), copper (−0.26 ± 0.05), nickel (−0.27 ± 0.08), and vanadium (−0.24 ± 0.11); zinc flux was indistinguishable from zero (−0.03 ± 0.28); and a source for total manganese and filtered P (3.4 ± 0.8 and 17 ± 5, respectively). Sediments, on average, acted as a minimal net sink or source for filtered metals (−1.5–3.9). These results suggested that upriver sediments perform a valuable ecosystem service by removing P that otherwise could fuel cyanobacterial blooms in western Lake Erie. However, sediment P cycling requires further study at locations near the river mouth to determine whether the timing and magnitude of observed P effluxes contribute to cyanobacterial bloom formation. The results also highlight the seasonal and spatial variability of sediment behavior relative to P cycling along the river, emphasizing the need for more spatially and temporally intensive sampling to constrain internal river nutrient processing, which will help to accurately predict nutrient loadings and reduce HABs in Lake Erie.
Page Count
130
Department or Program
Department of Earth and Environmental Sciences
Year Degree Awarded
2021
Copyright
Copyright 2021, all rights reserved. My ETD will be available under the "Fair Use" terms of copyright law.
ORCID ID
0000-0002-5531-8919
