Meeting Abstract
Patterned landscapes are naturally occurring phenomena that can reveal major geological or ecological processes taking place in a variety of ecosystems. In a northern Florida salt marsh, there is an abundance of marsh ponds: vegetation-free, almost perfectly circular ponds that have previously not been studied. To begin to understand the origin and role of marsh ponds within salt marshes we evaluated the spatial organization, biogeochemistry, and ecology of the marsh ponds. Using ArcMap we found that marsh ponds were indeed spatially clustered (Average Nearest Neighbor: p<0.005; Global Moran’s I: p<0.005). We then took soil cores from a pond and a marsh site using a 1m long push core. We found that marsh ponds had higher ranges of organic matter deeper in sediment profiles (17.6% – 25.4%) compared to the neighboring marsh (3.9% – 8.7%). Additionally, marsh ponds had relatively high iron levels (1,410 mg/kg) deeper in the profile (62-64 cm depth) compared to the neighboring marsh (381 mg/kg). Our results suggest groundwater influence, which is a major feature of karst landscapes. We hypothesize that marsh ponds formed through karst dissolution. However, pore water samples measuring salinity, pH, and sulfide levels from varying depths found no evidence to suggest groundwater influence but these erratic measurements could be explained by a drought at the time of collection. Finally, we monitored the abundance of organisms in the ponds using crab and minnow traps. We found that blue crabs were more abundant in ponds than in nearby streams suggesting that marsh ponds act as refugia for small organisms. Overall, our work lays the groundwork for future studies examining the geologic processes underlying marsh pond formation as well as their ecological role in salt marshes.
