Award: OCE-1439504

Salt marshes are among the most productive ecosystems in the world. Salt marshes are also critical shoreline habitats, providing many ecological and economic services to humans, including sheltering coasts from erosion, filtering nutrients from terrestrial run-off, sequestration of carbon from the atmosphere, supporting shrimp, oyster and crab fisheries, and providing foraging and reproductive habitat for a variety of shorebirds and mammals. Despite these important benefits, 10-60% of marshes that once occurred on the Eastern U.S. seaboard have been lost to human development. Understanding how salt marshes are structured is necessary to protect remaining salt marshes and to restore degraded habitats. For nearly 50 years, the theory of salt marsh ecology has been that physcial factors such as salinity are the primary determinants of marshes. Results from this NSF research have overturned this theory and show that instead there are strong forces also occuring from the top-down. Specifically, my experimental field work reveals that blue crabs play a keystone role in the salt marsh food web by suppressing densities of plant-grazing snails that, when left unchecked, increase in numbers and destroy marshes and their vaulabe functions. Work supported by this grant has resulted in 24 publicaitons in journals and the publicaiton of the most popular gradute level text book in Marinec Ecology and Conservation. Two post-doctoral scholars, four graduate students, and eight undergraduate students where supported in part on this grant. Both post docs and two graduate students now have faculty positions, while all undergraduates are now in science PhD programs. Results from the research supported by this grant enables coastal managers to better predict potential effects of blue crab depletion on salt marshes and to formulate long-term plans to sustain these economically and ecologically important communities. Continued coastal development in the southern U.S. will undoubtedly result in even further fishery depletions in estuarine communities surrounding salt marshes. Understanding food web linkages and interactions and how these systems respond to such perturbations is critical to their survival. Without this research managers would not know that healthy blue crab populaitons can help protect salt marshes from the decimiating effects of drought and sea level rise. Blue crabs help protect marshes from climate cahge because in their absence snail numbers increase and act in concert with increasing drought to kill the marsh grasses even faster. Last Modified: 11/25/2014 Submitted by: Brian R Silliman