Submitted to: Proceedings of the Society of Wetland Scientists
Publication Type: Abstract Only
Publication Acceptance Date: April 7, 2009
Publication Date: N/A
Technical Abstract: In the southeastern USA Coastal Plain region, many inland surface water systems will meander through flat or depressional landscape areas prior to discharge into coastal estuaries. Slow water flow through these areas often causes flooding that promotes formation of in-stream wetlands with dense vegetation. In turn, combinations of slow flows and vegetation allow optimum conditions for the deposition of phosphorus (P)-rich sediments. Some Coastal Plain soils contain high P concentrations, and erosion can transport P-rich sediments into surface water systems. In-stream wetlands can be effective in storing and accumulating P-rich sediments. Little information exists, however, on how hydrologic disturbances caused by precipitation from hurricanes and tropical storms will influence sediment dissolved P (DP) releases into the overlying water column and shifts in their internal P storage pools. Dissolved P releases by in-stream wetlands and transport into coastal estuaries have immense importance on nutrient dynamics in these aquatic ecosystems. This presentation examines long-term P storage/release capability of two Coastal Plain in-stream wetlands, depicts shifts in P storage pools, and describes the effects of storms on DP export. In long-term (2 to 4 yr) studies, results showed that two in-stream wetlands were effective at reducing DP loads and concentrations in outflows. Regression analysis revealed a significant linkage between wetland outflows and DP release. The hydrologic disturbance, although variable between storm events, resulted in disproportionate annual DP releases. Monitoring DP stored in sediments using passive samplers and P sorbed to sediment corroborated shifts in internal P storage pools. Laboratory P sorption experiments and sodium pyrophosphate extractions on wetland sediments revealed that P sorption maximums were a function of the sediments' organic carbon content and that chelated aluminum and calcium were highly correlated with the in-stream wetland sediment total P concentrations. Coastal Plain in-stream wetlands can be effective P storage entities; however, hurricanes and tropical storms can flush significant quantities of DP out of these wetlands.