Biogeochemical cycling in an organic-rich coastal marine basin. 7. Sulfur mass balance, oxygen uptake and sulfide retention

Sulfur and oxygen fluxes were quantified in the seasonally varying anoxic marine sedimentary system of Cape Lookout Bight, N.C., U.S.A. Over the three year study period, 1981–1983, the mean annual sulfate reduction rate was determined to be 18.2 ± 1.6 moles · m⁻² · y⁻¹. This value, added to the estimate of the detrital sulfur input of 1.2 ± 4.4 gave a total sulfur input of 19.4 ± 4.7 moles · m⁻² · y⁻¹. The sulfide flux to the sediment-water interface, measured in anaerobic benthic chambers was 4.6 ± 0.5 moles · m⁻² · y⁻¹, and represented 37% of the annual oxygen uptake rate of 25.2 ± 2.8 moles · m⁻² · y⁻¹. The sulfide burial rate, determined to be 15.5 ± 3.1 moles · m⁻² · y⁻¹, was within 5% of the value predicted by summing the fluxes at the sediment-water interface. The CS">CS weight ratio of sediment below the depth of diagenetic reaction was determined to be 2.75.

The sulfide retention rate in these rapidly accumulating sediments (10 cm/yr) was 77 ± 19%. Comparison of this result with previous studies shows that rapid sediment accumulation and the lack of bioturbation control this unusually high degree of sulfide retention.