Spatial and Seasonal Patterns of Above- and Belowground Vegetation Biomass and Potential Drivers in the Pascagoula River Delta, MS

Coastal wetlands provide a valuable wealth of services to the greater coastal ecosystem and human communities. However, threats such as sea level rise and conservation projects, such as freshwater diversions, have the potential to alter coastal wetlands in different ways. In this thesis, I describe the effects of inundation and nitrogen on vegetation productivity using a field-sampling approach and an in situ controlled mesocosm experiment, called a marsh organ. The West Channel of the Pascagoula River contained significantly higher belowground biomass than the East Channel, which is more anthropogenically modified. Vertical distribution of belowground biomass did not strongly vary between seasons or channels. Elevation was significantly correlated to aboveground biomass, and NOx was correlated to belowground biomass. Both relationships were nonlinear and complex. In the marsh organ, Sagittaria lancifolia end-of-season biomass responded in a quadratic fashion, similar to coastal sedge and grass species in previous studies. My findings are valuable to understanding the status and resilience of the lower Pascagoula River, as well as the ability of S. lancifolia (a dominant fresh-brackish water marsh species) to respond to changing hydrological regimes, potentially including freshwater diversion