Coastal wetland loss is pervasive and linked to a combination of natural and anthropogenic drivers such as wave action, land use changes, and sea level rise. In some instances, eroding salt marshes have space to migrate inland, but this may come at the expense of losing other ecosystems such as freshwater marshes or forests. Installation of breakwaters—hardened structures built of oyster shell, rock, or concrete and placed parallel to the shoreline—are increasingly used to mitigate erosion by decreasing wave height, which in turn can alter the physical environment, including dissolved oxygen content and sediment grain size. Studies demonstrate breakwaters can decrease marsh erosion relative to unprotected marshes, but we lack an understanding of how they affect marsh nitrogen (N) cycling and removal. We investigated nitrogen biogeochemistry at a marsh complex situated along a freshwater-saltwater ecotone in Mobile Bay, AL. We measured potential rates of denitrification (DNF) and dissimilatory nitrate reduction to ammonium (DNRA) to evaluate how marshes with breakwaters of varying age (installed 7 and 12 years ago) affected nitrate reduction processes relative to unprotected control marshes. To separate physical effects of breakwaters (i.e., decreased wave height) from biological effects (i.e., potential changes in marsh vegetation), we measured potential DNF and DNRA rates in both unvegetated and vegetated areas. Preliminary results showed no differences in potential DNF (N removal) or DNRA (N retention) rates in unvegetated control marshes relative to unvegetated marshes behind breakwaters, suggesting physical changes behind breakwaters may not affect potential rates, although variation was high. We also found no differences in potential DNF or DNRA rates in vegetated control marshes relative to vegetated marshes behind breakwaters. Overall, these results suggest that marshes behind breakwaters function similarly to control marshes without breakwaters and that, despite other potential benefits, breakwaters did not enhance nitrogen removal ecosystem services.