Biogeochemical Processes Linked to Important Ecosystem Services in Restored and Natural Louisiana Wetlands

Wetlands provide an abundance of ecosystem services, including valuable habitats for wildlife, water quality improvement through biogeochemical cycling, flood protection, high rates of primary productivity, and sequestration of carbon and nitrogen. Louisiana contains 40% of the lower 48 United States coastal and estuarine wetlands and also has the highest rates of wetland loss, ~ 80% of the nation's total loss. Approximately 4900 km2 of coastal land in Louisiana has been lost since 1930. In the first project the study location, Barataria Bay, has one of the highest coastal wetland loss rates in the nation and therefore is a high priority for wetland restoration. Sediment dredged from the bed of the Mississippi River was placed at targeted locations in Barataria Bay and we sought to determine how comparable these dredged river-sediment marsh soils are to those of the surrounding natural marshes. Percent organic matter in the created marsh was 11.6% of the natural marsh. In the created marsh, the β-glucosidase enzyme activity was 10.3% and soil oxygen demand was 11.2% of the natural marsh, reflecting significantly less soil microbial processes within the created marsh sites. These data provide a baseline for monitoring and eventual determination of the trajectory for development of microbial-driven ecosystem services of created wetlands using dredged river sediment. Nitrogen loading from the Mississippi and Atchafalaya Rivers leads to an area of hypoxia each summer in the Northern Gulf of Mexico. Riparian wetlands within the Mississippi-Atchafalaya watershed could play an essential role in the reduction of nitrate released into the Gulf each year. However, much river-riparian wetland connectivity has been reduced through the building of levees. In an effort to restore these riparian systems, projects are focused on reestablishing the hydrologic connection of the river channel and riparian systems. The second project study location is located within the Atchafalaya River Basin, where these riparian wetlands will be reestablished with the Atchafalaya River. Results suggest that potentially 107 metric tons of N could be removed from the ~2023 hectare Atchafalaya Nature Preserve over a 3 month flooding period.