Influence of Burrowing Crabs on Salt Marsh Substrate Stability and Vegetation

Coastal marshes across the Northeastern United States have been documented to be declining. Causes for this decline likely include both biotic and abiotic factors due to changes from accelerated sea level rise and other anthropogenic disturbances. A possible biotic factor in marsh decline is increased perturbation from burrowing crabs. Uca species’ (fiddler crabs) populations have been shown to be increasing in many marshes in the eastern US, likely due to disruptions in food webs and expanding habitat from sea level rise. High densities of fiddler crab burrows have been shown to contribute to creek bank erosion and possibly in other factors of marsh instability. In this study, we experimentally test the impact of fiddler crabs on marsh substrate stability and marsh vegetation distribution in the high marsh by excluding crabs from some sections of a micro-tidal back-barrier marsh on Cape Cod, Massachusetts, and allowing them into others. We then compare vegetation cover, soil organic matter, elevation, and various soil stability metrics between manipulated crab burrow densities and un-manipulated densities.