2021 - Nature’s Filter: Wetland water quality before and after restoration in Plymouth, MA

Grant Award Year: 
Principal Investigator: 
Christine Hatch
Research Description: 
Natural and restored wetlands are among the most biodiverse ecosystems present in Massachusetts, providing unique habitat for species ranging from insects and endangered native fishes to coastal and songbirds, and plants which thrive in environments that range from completely saturated year-round to dry. Because this niche environment is crucially important for ecosystem services (including, but not limited to verdant habitat and food supply for a large diversity of plant, animal and insect species, water filtration, slowing and spreading of floodwaters, limiting erosion, storage of carbon and other nutrients, temperature buffering, pollinator habitat and forage lands, and water storage), significant attention has been paid to conserving and restoring wetlands and their optimum function wherever possible. Cranberry production has been a popular and profitable venture in southeastern Massachusetts for the past 150-200 years. In recent decades, the economic viability of cranberry farming in Massachusetts has declined due to increasing operating costs and growing competition from newer farms with more productive varietals in the Midwest and Canada (Hoekstra et al., 2019). Farmers looking for a green exit strategy to retire their farms are considering ecological restoration as an alternative to abandoning farms. There is evidence to suggest active restoration (farms that have been manually reconfigured and planted to encourage wetland species growth, hydrologic characteristics and hydric soil enhancement or mixing) begin to resemble a natural wetland faster than those simply left without human intervention (Living Observatory, 2020). Soil organic content, water table depth, plant assemblages and nitrate concentrations in actively restored wetlands more closely resemble natural wetlands than abandoned fallow, retired cranberry farms (which often results in recolonization of these former wetlands by upland species such as pitch pines due to an overly-deep water table beneath quickly-draining agricultural sand layers). While these characteristics are promising for active restoration, it is not known how quickly changes in water table and redox conditions will affect water chemistry. Therefore, it is important to quantify the rate of change after wetland restoration, to provide more robust predictions for restoration timescales and success. Of particular interest to this study is the improvement in water quality provided by functioning wetlands, in particular contrast to the net nutrient export (and potential for problems caused by excess nutrients) typically found in outflows of functioning cranberry bogs (Ballantine et al., 2017). We have a unique opportunity by partnering with the MA DER Cranberry Bog Program, which seeks to restore retired cranberry bogs into freshwater wetlands, and Living Observatory, a non-profit consortium of researchers and educators that share field sites, data, and knowledge of these systems (Living Observatory, 2020). For this work, we will quantify hydrologic conditions (water table elevations, using direct-push piezometers, and streamflow measurements), and test water samples for nutrient and other chemical concentrations. We plan to quantify the change in water quality from a fallow cranberry farm (4-years post-harvest) to a newly restored wetland (1-year post restoration) to provide a first look at nature’s filter in action. We foresee a continued interest in wetland restoration in Massachusetts as more cranberry farms are retired. Proof of positive changes in water chemistry play an important role in facilitating wetland development; so quantification of these properties can document the success of these efforts.