Coastal wetlands provide a number of ecosystem services. They are highly productive, buffer wind and wave energy, filter pollutants such as nitrogen (N) and phosphorus (P), and provide habitat for finfish, shellfish, wading birds, and waterfowl. Climate change-driven disturbance, sea level rise, and saltwater intrusion, compromise these services, especially N removal. In tidal freshwater forests and marshes, saltwater intrusion inhibits denitrification, desorbs ammonium-N from the soil cation exchange complex, and increases mineralization of soil organic matter that releases organic N. This is accompanied by a loss of soil elevation capital and a shift to an alternate stable state such as brackish marsh or open water.
Results/Conclusions
SALTEx, Seawater Addition Long Term Experiment, is a field experiment designed to test the effects of saltwater intrusion on nutrient (N, P) cycling, and community and ecosystem properties of a tidal freshwater marsh on the Altamaha River, Georgia, USA. Replicate (n=6) treatments consisting of continuous (press) and periodic (pulse) additions of dilute seawater are used to investigate the long-term effects of sea level rise and short term effects of low river flow or drought. Press additions lead to immediate (within several months) changes in biogeochemistry, plant community composition, and carbon (C) and N cycling that are exacerbated during the two years of treatment additions. Pulse additions of dilute seawater during low flow (autumn) conditions result in transient changes in ecosystem properties and services that return to their original condition once treatments are halted. SALTEx will reveal the order and pace of transformations that occur in freshwater wetlands as sea level rises and saltwater intrudes. Stay tuned…