Sediment Suspension and Elevation Loss Triggered by Atlantic Mud Fiddler Crab (Uca pugnax) Bioturbation in Salt Marsh Dieback Areas of Southern New England

Abstract

Smith, S.M. and Green, C., 2015. Sediment suspension and elevation loss triggered by Atlantic mud fiddler crab (Uca pugnax) bioturbation in salt marsh dieback areas of southern New England.The effects of bioturbation on sediment suspension and elevation loss by the Atlantic mud fiddler crab, Uca pugnax (Smith), were investigated in this study. High densities of U. pugnax occur in unvegetated areas of Cape Cod salt marshes that have been denuded by the herbivorous Sesarma reticulatum (purple marsh crab). The hypothesis addressed in this study is that U. pugnax then causes sediment suspension and subsequent erosion. Anecdotal evidence suggests that unlike vegetated zones sediments are rapidly eroding from dieback areas, but the various mechanisms by which this is occurring are unclear. In this study, we focused on the role that U. pugnax might play in this process through experiments that assessed sediment suspension during rainfall events and flooding tides, as well as elevation changes. The results indicate that U. pugnax contributes to elevated sediment loads in the water column and that the suspended sediment is transported elsewhere, resulting in elevation lowering. The loss of vegetation through S. reticulatum herbivory has resulted in a cascading series of events, with one of the consequences being an elevated potential for sediment mobilization and erosion by U. pugnax bioturbation. This has consequences for vegetation recovery and overall marsh resiliency.