Sulfate reduction rates, enumeration of sulfate-reducing bacteria, as well as pore water concentrations of NH,+ and titration alkalinity were determined for the upper 14 cm of sediments collected from 3 nearshore Bermudian environments: Coot Pond (LG), Mangrove Bay (MB) and Devil's Hole (DH). Sulfate reduction rates were rapld at LG and MB but slow at DH (-300 and 8.0 nmoles ml-' d-', respectively). Differences in source and deposition of organic matter caused rate variations. There was a linear relationship between sulfate reduction rates and sulfate-reducing bacteria. Pore water nutrient concentrations were low compared to clastic sediments. Nutrient regeneration rates, as calculated from organic matter C:N.P ratios, and sulfate reduction rates were used to calculate the turnover times of dissolved Pod3-and NH,+. Sediments subject to active bioturbation had NH,' turnover times 9 to 63 times less than those for non-bioturbated sediments