Low benthic mineralization and nutrient fluxes in the continental shelf sediment of the northern East China Sea

Abstract

The sediment oxygen uptake rate, vertical distributions of organic carbon content, sedimentation rate, and benthic nutrient flux were measured from May 29 to June 9, 2015, to evaluate the partitioned organic carbon and nutrient cycles in the sediment of northern part of East China Sea. The sediment oxygen uptake rate, measured by in situ and/or ex situ incubation methods were ranged from 5.81 ± 0.08 to 16.36 ± 0.08 mmol O2 m−2 d−1. The fauna mediated oxygen uptake rate were ranged from 5.80 ± 0.04 to 8.09 ± 1.52 mmol O2 m−2 d−1, showing a strong relationship with the benthic macrofauna biomass and density. The burial flux of organic carbon into sediment layer ranged from 0.26 to 2.04 mmol C m−2 d−1 (average: 0.92 ± 0.64 mmol C m−2 d−1), which comprised 0.5–4.2% (average: 1.9 ± 1.3%) of primary production. Burial efficiency ranged from 2.0 to 22.4% (average: 11.1 ± 7.0%). Low sediment oxygen uptake rate caused low effluxes of dissolved inorganic nitrogen (0.19 ± 0.03–0.73 ± 0.04 mmol N m−2 d−1), phosphate (−0.034 ± 0.004–0.016 ± 0.005 mmol P m−2 d−1), and silicate (0.30 ± 0.03–1.61 ± 0.06 mmol Si m−2 d−1), which accounted for less than 10% of the nutrients required for primary production in the water column.