12.12 Ecogeomorphology of Salt Marshes

The coupling of geomorphological and ecological processes is critical for the maintenance or disappearance of salt marshes. Emergent macrophytes dampen wave- and tide-generated shear stresses, promoting sediment deposition and marsh formation. The complex interactions among marsh primary productivity, sea level, and sedimentation determine the equilibrium elevation of the marsh platform and its resilience against external drivers. The strength of the root system can affect the ability of marsh edge scarps to resist erosion. Some marshes are commonly inhabited by a number of species of crab, whose burrows have been implicated in marsh-edge erosion, whereas mussels and other bivalves can be very important in stabilizing marsh sediment by both slowing wave and current velocities and binding sediment to the root mat. Nutrient enrichment has the potential to invoke negative feedbacks that will ultimately affect marsh geomorphic configuration and biogeochemical cycling, by altering plant production and community characteristics and increasing microbial decomposition of organic matter. In this chapter, we present a broad overview of the feedbacks between biota and sedimentological processes in salt marshes, including recent numerical models that have been utilized to study the ecogeomorphic evolution of intertidal areas.