EXPERIMENTAL DESIGN AND METHODS: Sediment cores were obtained in the field and transported to the laboratory for analysis within 24 hr. Sediment redox potential (Eh) was measured in 6 cm diameter cores using a platinum Eh probe coupled with a calomel reference electrode. The Eh electrode was lowered to designated depths in the core and allowed to react for 15 minutes or until readings were stable. Reading were corrected for the standard potential of the electrode-reference combination. By convention, depth in the sediment is given as negative values. Site (Current Name) , Site (Previous Name) BEN-PR-P22, BEN-PR-P2 BEN-PR-P24.2, BEN-PR-P0 BEN-PR-P14 , BEN-PR-P5 BEN-RO-R5.5 , BEN-SO-Row