Phosphorus recycling and burial in core sediments of the East China Sea

Phosphorus (P) recycling and burial in the sediment of the East China Sea (ECS) were investigated in October 2012. Dissolved Fe2+, Mn2+, PO43- and NH4+ in pore water and P species by sequential extraction as well as Fe oxides in core sediments were measured. The total P (P-Total) concentrations in core sediments ranged from 11.93 to 23.87 mu mol g(-1) and showed a decreasing trend from inshore to offshore on the ECS shelf. Detrital P (P-Detrital) was the main chemical form of P in core sediments, which accounted for 43-67% of P-Total. We found that the molar ratios of organic carbon (OC) to organic P (OC/P-Organic) were > 106 in all cores except for the inner shelf site DH3-1, as well as the middle shelf sites DH4-3 and DH3-8. The OC/P-reactive ratios (11-90) in all cores were much lower than the Redfield ratio, indicating the presence of excess P-reactive relative to OC in sediments of the ECS. The concentrations of P-CDB were well correlated with the Fecoa concentrations in the core sediments. The diffusive flux of PO43- across the sediment-water interface was estimated to be 0.12-1.42 mu mol cm(-2) yr(-1). The P-Total accumulation rates ranged from 6.1 to 20.7 mu mol cm(-2) yr(-1) and decreased with the distance from the coast. The P burial efficiency (PBE) was 93-99% of the sediment P-Total on the ECS shelf, which was comparable to the worldwide continental margin of the sediment, and most of the burial of P occurred as P-Detrital and authigenic P (P-CFA). The potential bioavailable P in the core sediments was estimated to be 6-20% of P-Total.