EFFECTS OF MUD FIDDLER CRABS, UCA PUGNAX (SMITH), ON SEDIMENTS OF SALT MARSH DIEBACK AREAS ON CAPE COD (MASSACHUSETTS, USA)

The effects of bioturbation on sediment suspension and loss by the Atlantic mud fiddler crab (Uca pugnax) was 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). Anecdotal evidence suggests that sediments are rapidly eroding from these areas but the various mechanisms by which this is occurring are unclear. This study focused on the possible role(s) that U. pugnax may play in this process. The results indicate that U. pugnax contributes to elevated sediment loads in the water column during simulated precipitation events and flood tides. Moreover, the sediment that is suspended is transported elsewhere, resulting in elevation loss. Thus, 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 by U. pugnax inhabiting the bare areas and, subsequently, erosional loss. This has consequences for vegetation recovery and marsh resiliency to other factors such as sea level rise.