GREAT LAKES RIVERMOUTH WETLANDS: IMPACTS OF LAKE LEVELS AND RIVER FLOWS ON WETLAND AREA

Great Lakes rivermouth ecosystems are biodiverse freshwater estuaries where lake water and river water mix, creating unique nutrient dynamics and wetland development. These coastal wetlands provide ecosystem services including recreation, food, and cultural value, and also hold intrinsic value as they are home to a wide variety of wildlife and plant communities. The understanding of the individual effects of lake levels and river flows on wetlands is well-established. However, the current understanding of the effect of dynamic interactions between river flows and lake levels on coastal wetland development is not well known. In this study, aerial photographs were interpreted to understand how wetland plant communities have changed on a decadal scale in response to long-term patterns in lake levels and river flows. Four rivermouth ecosystem sites on Lake Michigan were selected for this study, which varied in geomorphology and surrounding urban development. Wetland area and wetland vegetation type were delineated in ArcGIS from orthorectified historic photographs ranging from 1951 to 2016 at each site. Historic water level and streamflow data were also used to perform statistical analyses of rivermouth wetland response to fluctuations in lake levels and streamflow. The results showed less wetland area when both lake levels and river flows were high. The unique geomorphology of each site influenced wetland area and response to hydrologic drivers. The results of this study provide insight into the effects of climate change and anthropogenic stressors on Great Lakes wetland ecosystems and can help guide decision-making regarding wetland restoration, conservation, and urban planning.