Date of Award
Master of Science (MS)
Floating marshes are unique buoyant wetland systems that have the potential to move vertically with fluctuating water levels. Their distinct hydrology has the potential to allow them to be more resilient in the face of global sea level rise and potentially more vulnerable to salinity intrusion. Buoyant marshes have mainly been described in fresh inland and microtidal environments worldwide and there is a gap in research in mesotidal environments along the Atlantic coast. My objectives were to 1) identify and characterize potential floating marshes in the Savannah National Wildlife Refuge (SNWR) on the Georgia and South Carolina coast to 2) compare vegetative communities between floating and immobile marshes and to 3) determine the extent of floating marshes in the SNWR. To identify if floating marshes were present in the refuge, we monitored elevation change of the marsh surface, tracked water levels in adjacent tidal creeks, and analyzed marsh mat substrate for organic content. We found that all potential floating marsh study sites exhibited restricted vertical movement of the marsh surface and movement varied significantly between sites and seasons. We observed a weak to moderate linear relationship with adjacent tidal creek water levels and predominantly organic soils in all floating marsh sites. The stationary site that served as a control exhibited no vertical movement, contained dominantly mineral soils, and had no discernable relationship with tidal creek water levels. To investigate vegetation differences between floating and immobile marshes we used vegetation data collected biannually in June and October 2014 through 2020 to determine seasonal communities and compared vegetation structure and composition. In all study sites, we found that vegetation was not significantly different between floating and immobile marshes and floating marshes are restricted to the fresh and slightly oligohaline areas of the estuary. The restricted vertical movement and similarity of vegetative structure and composition of buoyant marshes to immobile marshes in the refuge may signal that floating marshes may not exhibit the expected resilience of other free-floating marshes against the effects of global sea level rise but may avoid enhanced negative impacts of salinity intrusion.
Waller, Jessica, "Identification and Characterization of Floating Marsh Communities in the Savannah National Wildlife Refuge" (2021). All Theses. 3527.