Organic carbon deposition and its control on iron sulfide formation of the southern East China Sea continental shelf sediments

Sulfate reduction rates and sedimentation rates were determined in sediments at ten stations on the southern East China Sea continental shelf. The area is characterized by relatively low organic carbon concentration with fast sedimentation rate. Rapid sulfate reduction rates, ranging from 1 to 4 mmol/m2/day, were observed. Organic carbon concentration varied from 0.3 to 0.6 wt%. Sedimentation rate varied from 0.2 to 0.7 cm/yr. In addition, normal marine S/C ratios were observed. Up to 96% of pyrite-sulfur was reoxidized before its final burial. Sulfate reduction rate and pyrite-sulfur burial rate increased linearly with increasing organic carbon burial rate, indicating that organic carbon deposition controlled pyrite formation in the East China Sea continental shelf sediments. The organic carbon utilized by the sulfate reduction and its burial represented a significant but relatively small fraction of the primary production in the studied East China Sea region.