| Sediment organic matter (OM) content varies widely among salt marshes of the USA mid-Atlantic coastline. This study examined sulfur and carbon cycle processes (sulfate reduction rates, decomposition, and root production) that influence OM accumulation in marshes.; Three treatments were established in two locations with different sediment characteristics in Phillips Creek Marsh (PCM) located at the Virginia Coast Reserve Long-Term Ecological Research (VCRLTER) site. Two of the experimental treatments were designed to alter the availability of terminal electron acceptors in sediment pore water by either removing fiddler crabs from areas with crab populations or by constructing artificial crab burrows in areas lacking crab populations. The third treatment, a reduced iron addition, was designed to lower pore-water sulfide concentrations. The results of the PCM experiments were used to explain the sediment OM content of six other marshes of the VCRLTER.; The presence of crab burrows significantly increased decomposition and decreased root production compared to the crab burrow-free treatment. Short-form Spartina aferniflora root growth was correlated significantly with sulfate reduction rates but not pore-water sulfide concentration. Plots with low OM generally had higher pore-water sulfide and lower pore-water sulfate concentrations than plots with more OM content. These differences could not be explained by differences in the sulfate reduction rate constants. The higher measured infiltration rates in the high OM content plots suggested that pore-water sulfide and sulfate concentrations potentially were influenced by the effect of sediment texture on the exchange of solutes between tidal water and sediment pore water. |
