Floating marsh systems are a unique category of wetlands characterized and named for the ability to float above the water column. Gasses generated via anaerobic metabolism in the organic substrates of these marshlands contribute to their buoyancy and vertical movement. This buoyancy allows for more direct water exchange between the substrate root zone and adjacent tidal creeks compared to rooted marsh systems. We characterized areas of perceived freshwater and oligohaline tidal floating marshes within the Savannah National Wildlife Refuge (SNWR) in South Carolina and Georgia, USA. At four sites across the refuge, vertical movement was monitored using pictures taken hourly by autonomous trail cameras and water level recorders were stationed in the interior of the marsh and in adjacent tidal creeks. Formal identification of floating marshes in this area would be novel and help identify which areas within the SNWR may be more responsive to changes in the salinity regime that could result from planned downstream dredging of the Savannah River channel.
Results/Conclusions
Results of ANOVA and post-hoc Tukey HSD tests revealed significant differences in vertical movement between all four sites. Simple regression analysis between vertical movement and adjacent creek magnitude showed a weak linear relationship. The differences in vertical movement suggest that there are floating marsh systems within the SNWR and that they have varying degrees of buoyancy. The weak linear relationship between vertical movement and adjacent water levels suggests that additional environmental variables including soil organic matter, average daily temperature, and interstitial salinity may need to be added to the model to allow for a more complete interpretation of factors influencing vertical movement for these particular floating marsh systems.