Student Author(s)

Grace Behrens, Hope College

Faculty Mentor(s)

Dr. Michael Philben, Geological and Environmental Sciences

Document Type


Event Date



Wetlands have a dual impact on the climate: a cooling effect caused by organic matter accumulation in anoxic sediments (removing carbon dioxide from the atmosphere); and a warming effect caused by methane emissions from these sediments. In this study, we analyzed the relative importance of both processes in interdunal wetlands in the Saugatuck Harbor Natural Area (SHNA). The SHNA wetlands are a unique ecosystem, dependent on high water levels in Lake Michigan. Thus, carbon accumulation in the wetlands may be ephemeral as the lake level falls. Our goal in this study was to evaluate the extent of carbon accumulation in the wetland sediments and to determine their potential methane emissions. To measure carbon accumulation, we collected sediment cores from seven slack pools within the wetland complex. The cores were split into 1-cm slices and their carbon and nitrogen content were determined using an elemental analyzer. Four of the five pools within the established wetland complex exhibited significant carbon accumulation (>25 g C m-2). Two incipient slacks with little established vegetation contained only minimal sedimentary carbon. We then measured the methane production potential of the slacks by incubating sediments from each pool in sealed bottles under an atmosphere of N2, to ensure anoxic conditions. Surprisingly, we detected methane production in sediment from all seven pools. In situ methane production at the incipient slacks is currently unlikely due to high oxygen concentrations but our results indicate that microbial communities in these sediments maintain the capability of methane production if oxygen is depleted. Ongoing research in these wetlands includes characterizing the microbial community.


This research was made possible through support by the Nicholas Ver Hey ’75 Geology Summer Research Fund.