Ecological processes in salt marshes of the southeastern U.S. have historically been considered to be controlled largely by bottom-up forces (i.e. nutrient cycling, salinity, productivity), however, recent studies have demonstrated that top-down pressures such as herbivory and predation can be just as or more influential in the regulation of these ecological processes. Barrier islands of the southeastern U.S. support dense populations of top order consumers such as the American alligator (Alligator mississippiensis). Starting in 2007, we initiated a study on Sapelo Island, Georgia to assess A. mississippiensis utilization of marine resources and to test the potential top-down effects this apex predator has in southeastern salt marshes. The study includes mark-recapture, stomach content removal, stable isotope analysis, and GPS/UHF telemetry of A. mississippiensis inhabiting the island. Preliminary results from this study indicate an increasing reliance on marine resources with increasing age and the use of movement between freshwater and marine environments to cope with the osmotic stresses of the highly saline salt marsh. While the impact and importance of this linkage system is still unknown we hypothesize the addition of an apex predator in salt marsh food webs of the southeastern U.S. will have a significant impact on the dynamics governing biodiversity and function. In addition, A. mississippiensis is a known ecosystem engineer and keystone species in many freshwater habits; however when subsidized from outside ecosystem boundaries these relationships within the terrestrial and freshwater ecosystem may change.