Salt Marsh Response to Dynamic Environmental Change

Abstract

Salt marshes are some of the world’s richest ecosystems and provide a plethora of benefits to coastlines and bays in terms of storm protection and chemistry. To ensure salt marsh survival under increasing rates of sea level rise, management practices have been trending towards natural sustainability measures to increase marsh resilience. To benefit these efforts, it is necessary to understand how natural salt marshes respond to environmental change in terms of sediment deposition and evolution of vegetation and open water. This study uses aerial image digitization to understand how Nauset Marsh in Cape Cod MA, a protected salt marsh on Cape Cod National Seashore, has responded to sea level rise and half a century of inlet migration. Digitized images from 1974-2019 were used to track changes to vegetation extent and open water features during study periods of different inlet migration stages. Observed changes were used to ascertain trends of marsh loss or adaptation based on previous research on ponding cycles and vegetation extent. Results indicate that Nauset Marsh has been relatively stable over the last half century, with the most significant change observed in Vegetated Marsh loss of 6.71% ± 3.19 primarily due to edge erosion near the present-day inlet. Despite net feature stability, significant differences in feature evolution trends were observed during different stages of inlet migration. Most notably, inlet breaching and migration correlated with dynamic feature changes throughout the marsh, while the static inlet period correlated with expansion of open water features near the inlet location. The evolution of Nauset Marsh suggests that inlet migration improves marsh resilience through periodic increases in sediment deposition in a natural salt marsh with sufficient sediment supply.