Faculty Mentor(s)
Suzanne J. DeVries-Zimmerman, Geological & Environmental Science; Dr. Michael Philben, Geological & Environmental Science
Document Type
Poster
Event Date
4-12-2024
Abstract
Interdunal wetlands/slacks occur in Lake Michigan's coastal dunes where the wind scours the sand to the water table. Since May 2016 we have performed ecohydrological studies on the largest interdunal wetlands/slack, ~1.25 ha in size, lying within a deflated parabolic dune east of Lake Michigan at the Saugatuck Harbor Natural Area, Michigan. The slack’s hydrology is influenced by Lake Michigan-Huron, appearing and increasing in size and water depth with rising lake levels and decreasing in size to drying with low levels. Prior to 2014, the slack was completely dry and dominated by upland dune species due to low lake levels. In 2014, rising lake levels rewetted the slack. Pools of standing water and hydrophytic vegetation appeared and expanded. While the surface waters of the pools are often supersaturated with O2 due to photosynthesis, bottom waters at the sediment interface exhibit low O2 saturation, allowing for the accumulation of organic matter from algae and cyanobacteria as well as emergent wetland vegetation. Surface and groundwater sampling indicate denitrification and sulfate reduction processes in the wetlands. Average total alkalinity in the slack pools, determined by titration, ranged from 3.57 meq/L (winter 2021) to 2.55 meq/L (June 2023) with a low of 1.67 meq/L (July 2021). Beginning in July 2021 and continuing to summer 2023, the titration data exceeded the acceptance criteria for carbonate speciation, suggesting that accumulating organic matter and the associated organic acids were a potential source of non-carbonate alkalinity. Many total alkalinity models assume a carbonate-based system wherein non-carbonate/organic alkalinity is discounted. However, our research finds that the organic fraction of total alkalinity can be considerable. Hence, care must be taken in using total alkalinity values to assess the buffering capacity, especially with respect to CO2 calculations, for these freshwater systems.
Recommended Citation
Repository citation: Huff, Faith, "Potential Non-carbonate Buffering in an Interdunal Wetland/Slack Along Lake Michigan" (2024). 23rd Annual A. Paul and Carol C. Schaap Celebration of Undergraduate Research and Creative Activity (2024). Paper 41.
https://digitalcommons.hope.edu/curca_23/41
April 12, 2024. Copyright © 2024 Hope College, Holland, Michigan.
Comments
Funding was provided by the Richard C. Hoeksema Geological Sciences Undergraduate Research Fund, Global Water Research Institute and the Department of Geological and Environmental Sciences, Hope College.