EXPERIMENTAL DESIGN AND METHODS: Sediment cores were obtained in the field and transported to the laboratory for analysis within 24 hr. For data that corresponds to a "INT TOP" and "INT BOT" entry, sediment cores for porewater extraction were sectioned by depth (in a glove bag under N2 for any samples that have HS- or PO4 -3 data). Porewater was removed from muddy sediments by centrifuging sections of mud for 15 minutes. At sandy sites it was necessary to use a "split" centrifuge tube with filter support. Centrifugation for 15 minutes forces porewater though the filter into the bottom of the tube. Nutrients, sulfides, pH and alkalinity in porewaters were analyzed (see ANALYTICAL METHODS). For data that donot correspond to a "INT TOP" and "INT BOT" entry, porewater samples were obtained through the use of a whole-core squeezer. Teflon filter rods were inserted into holes drilled at intervals along the core tubing. Pressure was slowly applied (vertically), and water was extracted into syringes. Additional NH4+ and salinity porewater data resulted from experimental work conducted between March 1999 and May 2000 and may be found in the file: BEN-PR-Sediment_NH4_Salinity_Project.xlsx. This data set also includes porosity, bulk density, and some organic carbon and total nitrogen data. Some reported NO3 values are below the dectection limit (0.1µM) of the analysis , but numerical values are retained to prevent their exclusion from summary calculations. HS values of 0 are also below the detection limit of the analysis (1µM); however, in the context of esturaine biogeochemistry, a 0 value for HS- is useful for describing freshwater or highly oxidized sediments. Site (Current Name) , Site (Previous Name) BEN-PR-P22, BEN-PR-P2 BEN-PR-P22 (Intertidal), BEN-PR-P2 (Intertidal) BEN-PR-P24.2, BEN-PR-P0 BEN-PR-P14 , BEN-PR-P5 BEN-RO-R5.5 , BEN-SO-Row BEN-RO-R8C BEN-RO-LPC BEN-RO-R8M BEN-RO-LPM