AGRICULTURAL INFLUENCE ON BIOGEOCHEMICAL STORAGE IN GEOGRAPHICALLY ISOLATED WETLANDS IN THE DOUGHERTY PLAIN

The Dougherty plain of Southwest Georgia is characterized by karst geology containing series of geographically isolated wetlands (GIWs). GIWs offer flood mitigation, pollution filtration and habitat to biodiversity. However, despite the ecosystem services they provide, GIWS are excluded from legal protections. The presence of groundwater irrigation in the region hosts intense agriculture which can degrade wetland water quality. Based on topography and hydrology, wetlands that are within or adjacent to major crop fields can receive significant sediment runoff. The sediment carries essential reactive nutrients (N, P, and organic C) that are stored within the system, yet the spatial and temporal storage of these nutrients are less understood. Here, we investigated the biogeochemical impacts of agricultural runoff on GIWs through the implementation of paleolimnological techniques. The primary objective was to determine the spatial and temporal impacts on nutrient delivery and deposition in GIWs located in agricultural and undisturbed areas. Surface sediment samples and sediment cores were gathered from an agriculture influenced wetland and an undisturbed wetland located near the Joseph Jones Ecological Center. Findings show high organic matter present in the top sediment layer (0-2cm) in undisturbed wetlands (36% OM) compared to agriculture wetlands (11% OM) exhibiting short term storage. However, values drop substantially downcore due to diagenesis and rapid plant uptake. Conversely, agriculture wetlands exhibit long term storage of organic matter with higher concentrations extending deeper into core stratigraphy. Nutrients (N and P) followed similar trends with N mirroring organic matter and P showing greater storage potential. Spatial distribution of sediment deposited in the system differs with undisturbed wetlands displaying heterogenous organic matter accumulation in comparison to homogenous distribution in agriculture wetlands due to fertilizer influence and lack of dominant vegetation. This study demonstrates the ability of agricultural wetlands to provide unique storage habitats for nutrients thus furthering the importance of such environments. These results can aid in forming recommendations to stakeholders on best practices to preserve the quality of aquatic ecosystems.