Effects of organic amendments on sulfate reduction activity,H2 consumption,and H2 production in salt marsh sediments

Sulfate reduction activity (SRA) was measured via the radioactive tracer (³⁵SO₄ ⁼) technique in sediment samples from the Canary Creek Marsh in Lewes, Delaware. Basal levels of SRA ranged from 130 to 319 nmoles of sulfate reduced/gram dry sediment/hour. With the exception of lactate and formate, all organic acids tested resulted in no stimulation of SRA, whereas straight chain alcohols (C₁-C₄) all gave a significant increase in SRA. In addition, H₂, glucose, and cellobiose caused a twofold or greater increase in SRA, while cellulose amendments did not alter SRA. Molybdate, an inhibitor of sulfate-reducing bacteria (SRB), caused a total inhibition in SRA. 2-Bromoethanesulfonic acid (BES), an inhibitor of methanogenic bacteria, caused a slight decrease in SRA. Hydrogen was not produced in detectable quantities in unamended samples but was produced in large amounts in glucose-amended samples. Hydrogen was rapidly consumed in unamended samples with molybdate additions causing a significant decrease in the rate of H₂ consumption. A variety of organic amendments was found to stimulate H₂ uptake. These studies suggest that SRB are stimulated by a large variety of organic amendments in situ and that SRB play a major role in maintaining low partial pressures of H₂ in marsh sediments.