Submitted to: Journal of Environmental Quality
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/18/2006
Publication Date: 4/5/2007
Citation: Novak, J.M., Szogi, A.A., Stone, K.C., Watts, D.W., Johnson, M.H. 2007. Dissolved phosphorus export from an animal waste impacted in-stream wetland: Response to tropical storm and hurricane disturbance. Journal of Environmental Quality 36:790-800. Interpretive Summary: Wetlands serve an important water quality function by storing phosphorus (P). Their ability to store P, however, can be overwhelmed through high rainfall and flooding caused by hurricanes and storms. Phosphorus flushed out of wetlands by tropical storms and hurricanes can cause significant chemical disruption in North Carolina coastal water quality. We conducted a 4-yr study that examined relationships between P and water volumes released from a wetland after storm activity. During this study, several tropical storms and hurricanes passed over the Coastal Plain region of North Carolina. Between these storms, we measured large differences in the amounts of phosphorus and water volume released from the wetland. Water volume discharged from the wetland increased; thereby causing more phosphorus release. The largest P release occurred in 1999 after Hurricanes Dennis, Floyd, and Irene. These three hurricanes deposited record setting precipitation totals that flooded the wetland resulting in very high P release. Wetlands can store P; however, their ability to retain phosphorus is severely reduced when tropical storms and hurricanes cause more water to flow out of the wetland.
Technical Abstract: The ability of wetlands to retain P makes them an important landscape feature that buffer P movement. However, their P retention ability can be compromised through hydrologic disturbances caused by hurricanes and tropical storms (TS). This study had three objectives: 1) to determine the effects of hurricanes and TS on dissolved phosphorus (DP) concentrations and loads discharged from a Coastal Plain in-stream wetland (ISW); 2) to evaluate shifts in the P storage pools that would reflect P accretion/removal patterns; and 3) to determine if relationships exist between storm characteristics with the release of DP and water volume discharge. From January 1996 to October 1999, the ISW's outflow DP concentrations and flow volumes (Q) were measured and they were used to calculate DP mass export loads. In addition, the sediment total phosphorus (TP) concentrations were measured, and both the water column and sediment pore water DP concentrations were examined using passive samplers. In several instances, TS facilitated greater DP releases than a single hurricane event. The largest release of DP occurred in 1999 after Hurricanes Dennis, Floyd, and Irene. The large differences in DP exports were explained by Q variations. Storm activity also caused changes in sediment pore water DP and sediment TP concentrations. This study revealed that some TS events caused higher DP releases than a single hurricane; however, multiple hurricanes delivering heavy precipitation totals significantly increased DP export.