Spring 2021 eNewsletter

Featured Research: Graduate Research Fellow Update
The Influence of Extreme Water Levels on Coastal Wetland Extent across the Laurentian Great Lakes

Olivia Anderson, Central Michigan University

Graduate Research Fellow (CMU), Olivia Anderson. Photo credit: Olivia Anderson.

Great Lakes coastal wetlands (GLCW) are immensely productive ecosystems that provide many ecosystem services for the Great Lakes region: they protect water quality by filtering and retaining excess sediments and nutrients, protect shorelines against flooding and erosion, and provide habitat for numerous species including fish, birds, and anurans. Services like these rely on robust plant communities that are hydrologically dependent on the Great Lakes. However, in recent years, the hydrologic regime of the Great Lakes has been shifting. The concern is not simply a rise from low to high water (given that Great Lakes water levels normally vary across years, seasons, and hours), but a shift in the frequency and magnitude of fluctuations away from historic patterns. For example, an extended low period occurred across the 2000s and early 2010s, whereas beginning in 2015, water levels of the Great Lakes have been reaching all-time highs. Wetlands can moderate the impact of increased water levels via migration when shoreline barriers like roads are absent. However, because there is a lag period between water level shifts and wetland migration, water levels could change faster than wetlands can migrate. This could result in decreases to wetland extent and integrity, subsequently diminishing the ability of GLCW to provide ecosystem services.

Olivia Anderson is a biology master’s student at Central Michigan University (CMU) and a 2020–2021 CIGLR Graduate Research Fellow recipient. With her advisor Dr. Donald Uzarski, co-mentor Dr. Casey Godwin (CIGLR), and committee members Dr. Anna Harrison (CMU) and Dr. Benjamin Heumann (CMU), Olivia has developed a study to better understand how GLCWs shift with extreme changes in water levels. This research will provide insight on how water levels may influence GLCW size and, as a result, GLCW ecosystem services, providing further support for coastal wetland protection and restoration in the Great Lakes region.

Coastal Wetland Monitoring Program (CWMP) data (greatlakeswetlands.org) are the foundation of Olivia’s study. Not only does this EPA-funded program span the entire Great Lakes region (U.S. and Canada), but it also covers both the recent low- and high-water periods of the Great Lakes from 2011–2020. The CWMP samples for water quality, vegetation, fish, birds, anurans, and invertebrates to gauge the level of disturbance among wetlands. All sites are sampled on a five-year rotation, and there are over 600 sites that have vegetation data (Olivia’s dataset). Wetlands that are sampled must be larger than four hectares, be dominated by herbaceous or emergent vegetation, and have a surface connection to a Great Lake.

Figure 1. Example of a drastic visual change in wetland size featuring Petobego Pond in Traverse City, MI, from April 2012 (left) to May 2018 (right).

“Observational data suggest that various wetlands across the region have moved closer to shore or decreased in size from 2011–2020,” says Anderson (Figure 1). For an empirical analysis, Olivia is using transect data from CWMP vegetation sampling to generate variables that describe wetland vegetation extent, proximity to the shoreline, and inundated extent. “By relating these variables to water levels, I will be able to demonstrate how wetland size varies along a gradient of water elevation.”

In addition to using CWMP transect data, Olivia also hopes to generate wetland extent variables using satellite imagery, which would allow for comparison of the field collected data methods to imagery methods. “Fieldwork locations are not always accessible and easy to sample,” says Anderson. “It also takes a lot of effort to implement a long-term sampling project for a multi-year trend analysis. Using satellite data, on the other hand, is much more time efficient, cost effective, and covers more area.” If the imagery and transect results are comparable, Olivia’s study could be expanded to other sites within and across GLCWs as well as other regions.

“I intend to improve understanding of how Great Lakes coastal wetlands have shifted with water level rise and lay a foundation for continuing to track trends in how wetland extent is affected by changes in long-term water levels across the Great Lakes,” says Anderson.

Olivia Anderson was a 2020-2021 CIGLR Graduate Research Fellowship recipient. She is pursuing an M.S. degree in Biology from Central Michigan University working with advisor Dr. Donald Uzarski. This fellowship enabled Olivia to focus on research and development of her study; expand her professional network by collaborating with CIGLR, specifically her co-mentor Dr. Casey Godwin; and present a poster at the upcoming 2021 IAGLR conference.