Date of Award
Michigan’s wetlands, and their invaluable natural services, were declining at an alarming rate; therefore, the process of wetland mitigation was introduced in 1979 to offset this loss. From 2003-2006, a series of mitigated wetlands were installed to compensate for the wetlands removed during the construction of the M-6 highway south of Grand Rapids, MI. The objectives of my research were to determine whether these man-made wetlands function similarly to natural wetlands in terms of biological integrity, further develop methods for a macroinvertebrate-based index of biological integrity for inland wetlands, and provide pragmatic suggestions for wetland mitigation practices. Macroinvertebrate, plant, and water samples from mitigated and natural wetlands were collected. Macroinvertebrate samples were applied to appropriate bioassessment indices developed by Uzarski et al. (2009) while plant samples were applied to analyses developed by the Michigan Department of Natural Resources (Herman et al. 2001) to indicate biological integrity. Floristic quality analyses yielded varying results, yet the mitigated and reference wetlands were statistically similar in terms of invasive plant coverage, floristic quality index, and species richness. The macroinvertebrate index of biological integrity scores for the reference wetlands indicated significantly healthier ecosystems than their mitigated counterparts. The macroinvertebrate and plant bioassessments yielded different results, which is concerning since most agencies use floristic quality assessments as the primary means to evaluate wetlands. This divergence can be attributed to dissimilarities in ecosystem characteristics between mitigated and natural wetlands, some of which are successional processes and heterotrophic or autotrophic dominance. Suggestions for wetland mitigation practices include: wetland location chosen near large pre-existing wetlands to facilitate connectivity and interaction of more species, inoculation of less motile macroinvertebrate species for isolated wetlands to help expedite colonization, and prolonged maintenance of established wetlands to limit invasive species.
Neal, James N., "Evaluating the Success of Wetland Mitigation in West Michigan: A Macroinvertibrate-Based Approach" (2014). Masters Theses. 337.