AN INTEGRATED APPROACH TO EROSIONAL PROCESSES AT A NEW ENGLAND SALT MARSH

Increased rates of sea-level rise (SLR) due to anthropogenic climate change threaten many coastal environments. At Barn Island Wildlife Management Area, a coastal salt marsh in Stonington, CT, USA, we examined the interaction between the physical and ecological factors that shape the marsh-bay edge.

Marsh stability is influenced by marsh grasses and mussels. Over the four years of this study, we observed shifts in marsh grass diversity and density. With reduced root stabilization, the edge progressed from a normal slope to a vertical cliff. We have observed roughly half of the ~200 m of measured shoreline change its profile at least once in our four years of observation.

Although the byssal threads of mussels are thought of as a stabilizing force, mussels may also contribute to erosion. During this study, Barn Island’s marsh edge has exhibited decreases in mussel population. On slumped edges that have experienced significant erosion due to wave undercutting; however, mussel populations have increased. As sea level rises and inundation time increases, the weight of mussels on slumped edges may further exacerbate erosion and cause the marsh edge to migrate inland.

We found marsh edge erosion proceeds as a cycle in which single-event breakage of marsh edges is preceded by months or years of gradual change. The cyclic mechanisms of marsh edge erosion are likely controlled by the rate of SLR, elevation, location and human disturbance at each site. One or more of these factors may override the physical and ecological defenses that slow down erosion.