RELATIONSHIPS AMONG HYDROGEOMORPHOLOGY, WETLAND DISTRIBUTION AND WATER LEVELS OVER TIME IN ESTUARINE ENVIRONMENTS

Estuaries are dynamic systems characterized by hydrologic mixing, where water, energy, sediment and nutrients from both river and receiving water unite to form a unique yet variable environment. Water levels in estuaries are thus defined by, and subject to, streamflow from the river and sea-level fluctuations. Long-term fluctuations in water levels affect hydrogeomorphic structure, as well as wetland structure, distribution, and composition. A better understanding of these dynamics will help us to comprehend the processes that govern changes in wetland distribution, and thus the breadth of the ecosystem services that estuarine wetlands provide. To this end, this study examined how wetland plant communities have changed through time in relation to long-term changes in water levels, and therefore hydrogeomorphic structure, using historic air photo interpretation in three freshwater estuaries on Lake Michigan that are functionally similar to saltwater estuaries of the Northeast. Additionally, through using historic water levels to determine effects on wetland plant communities, observed patterns are being used to inform our predictions for the future in light of climate predictions. Previous studies and preliminary data from this study show that higher water levels are correlated with less emergent vegetative cover, suggesting that wetland impacts will depend on local water levels and hydrogeomorphic structure. However, armored and altered sites show different results compared to unmanaged sites, with water levels in unaltered sites responsible for more natural year-to-year variations in hydrogeomorphic structure and wetland distribution. It is important to realize not only the extent to which humans are affecting estuarine systems, but also the interplay between water levels, hydrogeomorphology, and wetland ecology within these systems themselves, so as to better understand the necessary steps for restoration.