Tuesday, May 19, 2009 - 11:00 AM
149

Internal eutrophication by sediment phosphorus release in a restored wetland

Lauren E. Kinsman1, Jonathan M. O'Brien2, and Stephen K. Hamilton1. (1) Kellogg Biological Station, Michigan State University, 3700 East Gull Lake Drive, Hickory Corners, MI 49060, (2) Kellogg Biological Station, 3700 East Gull Lake Drive, Hickory Corners, MI 49060

Phosphorus (P) availability tends to be regulated by sediment P sequestration, which in turn is strongly affected by periodic desiccation.  Work in Dutch fens shows that sediment desiccation re-oxidizes iron binding sites, causing net sediment P retention upon reflooding, whereas organic sediments of the Florida Everglades have shown net P release after drying and reflooding.  We monitored water and sediment chemistry before and after flooding at a wetland restoration.  Sediments had an average of 54% organic matter, 1225 ugP/gdw, and 0.74 mg HCl-extractable Fe/gdw.  Immediately after flooding, all surface waters had higher soluble reactive phosphate (SRP) concentrations than before.  Sites that had been inundated prior to flooding increased by 78 and 227%.  Sites that began the year inundated, but had dried prior to flooding increased by 99 and 711%.  Previously dry areas had SRPs of 300 and 747 ugP/L.  Duckweed and filamentous algae reached high abundances, likely in response to P release.  Three months after flooding, three of four previously wet sites continue to have higher SRP. Measurement of sediment P binding fractions before and after flooding is ongoing.  Reflooding historically drained wetlands for restoration is a common practice, but may cause sediment P release and internal eutrophication.


Web Page: Internal eutrophication, phosphorus, wetland restoration