THE IMPACT OF SOIL CHARACTERISTICS AND SEA LEVEL RISE ON PHOSPHORUS DYNAMICS IN COASTAL AND UPSTREAM WETLANDS IN THE LOWER CHESAPEAKE BAY

Aquatic systems are adversely affected by excess inputs of phosphorus (P) mobilized from extrinsic and intrinsic sources. Despite management improvements in most basins limiting extrinsic nutrient fluxes, associated eutrophication problems remain in most global fluvial and coastal ecosystems. Wetlands have been known as important sinks of terrestrially derived nutrients but progressive sea level rise and associated prolonged inundation of wetlands have the potential to change the biogeochemical characteristics of wetland soils and thus to influence the P retention/release dynamics in wetlands. This study uses 111 soil cores along 28 transects perpendicular to the streams to examine P dynamics and associated soil biogeochemical characteristics in five upstream and coastal wetlands in the lower Chesapeake Bay basin. Soil properties including total soil P, cation exchange capacity (CEC), degree of P saturation (DPS) and soil organic matter (SOM) were analyzed to understand the retention and release of P from wetlands into adjacent aquatic systems. Preliminary results from two drainage systems analyzed shows that SOM are relatively lower in the upstream wetlands (2.56 % ± 0.2, 16.14 % ± 0.93) compared to coastal/downstream wetlands (30.8 % ± 1.1, 20.85 % ± 0.55, 9.16 % ± 0.51). Likewise, Melich-3 soil P is greater in the downstream/coastal wetlands (12.6 ppm ± 0.7, 31.7 ppm ± 1.05, 29.6 ppm ± 0.95) than upstream (6.36 ppm ± 0.46, 10.56 ppm ± 0.53). CEC and DPS were also significantly higher in coastal/downstream wetlands than upstream wetlands. These preliminary results suggest the important roles of varying stream water salinities, wetlands soil characteristics, length of inundation and urbanization-related addition of cations in influencing P sorption/desorption dynamics in wetland soils. Completion of this study will provide insight into the role of wetlands in P fluctuations in the Chesapeake Bay waterways.