Disturbance type affects the distribution of mobile invertebrates in a high salt marsh community

Salt marshes are frequently exposed to storm overwashes resulting in large deposits of sand and wrack at the margin of the high marsh and sand dune communities. On Cape Cod, MA, these disturbance-generated areas are dominated by burrows of the crab Uca pugilator and by nest entrances of the ants Formica subsericea and Tetramorium caespitum. We mimicked the effects of storm deposits through additions of sand and wrack and examined their effects on the distributions of the biotic structures of these organisms. We found that while crabs responded negatively to sand deposition, ants did so positively. We suggest that soil temperature and moisture explain these patterns. Wrack deposits extend higher the zone of moist soil and decrease evaporative stress for marine organisms such as crabs, whereas sandy areas tend to be drier and preferred by terrestrial ants. We conclude that disturbance type influences the distribution of these marine and terrestrial organisms over the ecotone.