November 2024 eNewsletter

Assessing Drivers of Spatial and Temporal Greenhouse Gas Dynamics in Laurentian Great Lakes Coastal Wetlands
.

“This CIGLR postdoctoral fellowship provided me with the chance to investigate important questions about our Great Lakes ecosystems, as well as explore topics that personally intrigued me. Additionally, it gave me a head start on data collection that I am now using to shape my future research program.” -Amanda Suchy, PhD

Coastal wetlands are crucial ecosystems for maintaining clean water. They effectively remove pollutants due to their high organic matter and low oxygen soils, which promote microbial processes that eliminate pollutants such as nitrogen. However, these same processes that make wetlands excellent at removing pollutants also produce greenhouse gasses like methane and nitrous oxide. Currently, the Laurentian Great Lakes lack comprehensive measurements of greenhouse gas emissions from its associated wetlands. 

Amanda Suchy, PhD (Central Michigan University) along with mentors Don Uzarski, PhD (Central Michigan University) and Casey Godwin, PhD (U-M, CIGLR) addressed this information gap by leveraging ongoing monitoring programs to gather greenhouse gas emissions data from more than 100 coastal wetlands throughout the Great Lakes basin. “To gather samples from a large number of wetlands, we leveraged the Coastal Wetlands Monitoring Program’s 2023 and 2024 summer sampling efforts,” said Suchy. “This program is a multi-institutional and international collaboration funded by the U.S. EPA, which assesses the condition of Great Lakes emergent marsh coastal wetlands larger than 4 hectares by sampling biota, water quality, and habitat.” 

Water samples containing dissolved gasses were extracted on site and later analyzed for methane and nitrous oxide concentrations. “So far, we have data from 67 wetlands sampled in 2023 and will have data from a similar number of wetlands sampled during summer of 2024,” said Suchy. “Additionally, we have been collecting dissolved gas samples every other month, including through the winter at six wetlands in Saginaw Bay, with data expected soon.”

Each sample was collected from an open water environment 10 meters from the wetland and from dominant vegetation zones within the wetland. “This approach allows us to compare greenhouse gas emissions between the wetland and open water, as well as between different types of vegetation within a wetland,” said Suchy. “So far, our preliminary analyses show methane concentrations that range from 192 to over 36,000 times the concentration expected if methane was only in equilibrium with the atmosphere. This indicates that the water is always supersaturated with methane. We also saw nitrous oxide concentrations that ranged from near equilibrium values to 10 times the expected concentrations.” 

To date, this study has revealed that vegetated wetland areas have higher methane concentrations compared to open water areas, whereas open water areas exhibit higher nitrous oxide concentrations. “We also discovered that wetlands experiencing higher levels of human impact exhibited increased greenhouse gas concentrations,” said Suchy. “These initial findings indicate that Great Lakes coastal wetlands can emit significant amounts of greenhouse gasses, highlighting the need for further research into the factors driving these emissions.”