Sediment Organic Carbon Oxidation and Benthic Nutrient Flux in the Continental Shelf of the Southern Yellow Sea

We investigated the total sediment O₂ uptake (TOU), sulfate reduction rate (SRR), and benthic nutrient flux (BNF) at the Yellow Sea cold water mass (YSCWM) sediments (N3509 and N3507) and the coastal sediment (N3503) in the southern Yellow Sea. The organic carbon (OC) content increased from coarse- to fine-grained sediment, which was by far the highest at N3503 (0.89% and 6.1 Ø), followed by N3509 (0.72% and 4.5 Ø) and N3507 (0.15% and 3.0 Ø). The bottom water temperature at N3503 (16.0°C) was 6‒7°C higher than N3509 (10.2°C) and N3507 (9.0°C). The TOU and SRR at N3503 were 24.5 ± 5.0 mmol O₂ m^–2 d^–1 and 6.5 mmol S m^–2 d^–1, 3‒6 times higher than the values measured at N3509 and N3507 (5.5 ± 0.2 and 4.2 ± 0.3 O₂ mmol m^–2 d^–1 and 0.9 and 0.7 mmol S m^–2 d^–1, respectively). TOU showed a positive correlation with both the OC content and the bottom water temperature (R = 0.71, p < 0.001). The BNF at N3503 (3.4 mmol N m^–2 d^–1, 0.5 mmol P m^–2 d^–1, 3.8 mmol Si m^–2 d^–1) was 3‒37 times higher than the values measured at N3509. The BNF contributed 72–179% of the nutrients required for primary production at N3503, whereas the contribution was less than 30% at N3509.