EXPERIMENTAL DESIGN AND METHODS: Sediment cores were obtained in the field and transported to the laboratory for analysis within 24 hr. Four cores from each stations were sectioned by depth . Porewater was removed from two of the four cores by centrifugation and analyzed for free NH4+. Sediment sections from the other two cores were extracted with 2N KCL, then centrifuged and analyzed for exchangeable NH4+. Separate subsamples were used to determine porosity and bulk density. (see Weston et al. 2010. The effects of varying salinity on ammonium exchange in estuarine sediments of the Parker River, Massachusetts. Estuaries and Coasts 33: 985-1003). Site (Current Name) , Site (Previous Name) BEN-PR-P22, BEN-PR-P2 BEN-PR-P24 , BEN-PR-P1 BEN-PR-P14 , BEN-PR-P5 BEN-PR-P11 , BEN-PR-TL BEN-RO-R5.5 , BEN-SO-Row