Exploring the Use of Living Shorelines for Stabilization and Nutrient Mitigation in New England.

As salt marsh habitats face challenges due to sea level rise, storm events, and coastal development, there is an effort to use nature-based approaches such as living shorelines to enhance salt marshes and provide coastal protection. A living shoreline restoration and seasonal monitoring was conducted between July 2016 and October 2018 at an eroding salt marsh on Martha's Vineyard, Massachusetts, Northeastern USA to assess changes in two essential ecosystem services: shoreline stabilization and nitrogen removal. Neither the living shoreline nor unaltered sites demonstrated significant sediment deposition at the marsh edge or on the marsh platform between 2017 and 2018. While we expected nitrogen removal via denitrification to improve at the living shoreline sites over time as abiotic and biotic conditions became more favorable, we found limited support for this hypothesis. We found higher rates of denitrification enzyme activity (DEA) at the living shoreline sites when compared to unaltered sites, but these rates did not increase over time. This study also provides a qualitative assessment of our living shoreline structural integrity through the years, particularly following storm events that greatly challenged our restoration efforts. We demonstrate that living shorelines fortified solely with natural materials may not be the most effective approach to maintain these ecosystem services for Northeastern USA salt marshes exposed to intense northeasterly storms. We suggest the restoration of salt marshes to improve major functions be a priority among managers and restoration practitioners. Initiatives promoting the use of nature-based restoration solution where environmental conditions permit should be encouraged.