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Living shorelines and nitrogen mitigation on Martha's Vineyard, MA
Citation:
Schoell, M., S. Ayvazian, A. Pimenta, A. Gerber-Williams, Marty Chintala, D. Grunden, D. Cobb, C. Strobel, AND K. Rocha. Living shorelines and nitrogen mitigation on Martha's Vineyard, MA. Restore America's Estuaries, Long Beach, California, December 08 - 13, 2018.
Impact/Purpose:
Coastal environments along the Atlantic seaboard protect coastal communities from severe storm damage. Currently, these ecosystems are being adversely impacted due to many climatic factors and excessive nutrient enrichment. Many sorts of novel remediation techniques are being examined to mitigate these impacts to our coastline, including the use of living shorelines, which uses biodegradable materials such as coir fiber 'logs' and oyster shell bags. We tested the efficacy of using this approach along an eroding shoreline at Felix Neck Sanctuary on Martha's Vineyard, MA. While the study is on going our preliminary results indicate that rates of nitrogen removal were greater at the living shoreline sites than the non-living shoreline sites. This restoration work provides novel information about the utility of this technique and is relevant to environmental managers faced with coastal erosion and water quality challenges.
Description:
Increased human development along the coast and the subsequent increased delivery of excess nutrients to estuarine waterbodies can have combined deleterious effects on salt marsh ecosystems. An increasingly popular shoreline stabilization technique is the use of a living shoreline, which uses biodegradable materials such as coconut fiber coir logs and oyster shell bags that cup the marsh edge to reduce wave energy, enhance the robustness of existing marsh, and facilitate the growth of new marsh. In our study, we assess the potential of a living shoreline as a tool for enhancing nitrogen removal. This may result from improved marsh condition, marsh plants, and newly created marsh area. Between June and August 2016, living shorelines were constructed along an eroding salt marsh at Felix Neck Wildlife Sanctuary on Martha’s Vineyard, MA. The experimental design consists of three living shoreline sites with associated control sites, each spanning 80 meters of marsh edge. In addition to physical construction, we examined the spatial and temporal changes in denitrification rates of the marsh platform in the presence and absence of a living shoreline restoration site. Denitrification enzyme activity (DEA), a measure of potential denitrification, was measured in soil cores collected on the marsh platform in living shoreline and control sites seasonally beginning in July 2016. Field measurements included an annual survey of the eroding marsh edge using permanent elevation quadrats; sampling of aboveground biomass, soil percent carbon and nitrogen; and water quality monitoring in the tidal pond. Results showed that denitrification rates were higher in experimental sites than controls (p=0.02), but there was no significant difference in season or year. Additionally, there was a significant interaction (p=0.03) between treatment and distance from the marsh edge. DEA rates along the marsh edge and in the high marsh were not significantly different in experimental areas; however, rates were higher along the marsh edge than in the high marsh in control areas. There was also a negative correlation (r=-0.72) between DEA rates and flood duration, which may indicate ideal elevations for nitrification-denitrification coupling for the marsh. This restoration work not only provides novel information about the feasibility and success of living shorelines in New England, but can be particularly relevant to environmental managers and coastal communities facing coastal erosion and water quality challenges.