Salt Marsh Health and Biomass Responses to a Changing Environment

Coastal salt marshes are important ecosystems not only for their aesthetic beauty but also for their ecosystem services that they provide including improving water quality, providing protection from storm surges and hurricanes, and carbon sequestration. With climate change, including drought, warmer temperatures and sea-level rise, these systems are going to be impacted. Understanding how salt marshes will respond, or already have responded, to climate change will help us be better prepared for the future. By scripting a model to project how marshes may migrate with sea-level rise, I discover that salt marshes within Beaufort and Jasper counties, South Carolina will largely keep pace with sea-level rise. However, there are portions of the marsh area within these counties that will likely drown and development will impede areas of projected marsh migration. Additionally, I explored how above and belowground biomass changes with elevation above sea level, which are important relationships for modeling efforts. Using high-resolution satellite data, I mapped aboveground biomass across the entire marsh. Pairing this with elevation data, I created a growth curve of biomass versus elevation. The established growth curve is particularly useful as an input for biogeomorphic models of marsh development. Through computed tomography analysis, I analyzed belowground biomass. I found that belowground biomass is also a function of elevation, but there can be significant inter-site variability regardless of elevation. Looking at fall/spring variability, biomass abundance does not largely change, which indicates that belowground biomass is more likely longer lived. In the last part of this dissertation I looked at a past marsh dieback event to better understand drivers that lead to decline in marsh health. Using Landsat data, I created a map of change in salt marsh health by using differences in Normalized Difference Vegetation Indices. It is likely that the vegetation within higher elevations experienced stress due to hypersalinity, while vegetation within the lower marsh experienced stress from hypoxia leading to increased rates of vegetation decline in these zones. Overall this dissertation improves our understanding of drivers of marsh health and increases awareness of how salt marshes may respond under a changing climate