Distribution, flux and biological consumption of carbon monoxide in the Southern Yellow Sea and the East China Sea

Carbon monoxide (CO) concentration distribution and microbial consumption rate constants, along with atmospheric CO mixing ratios, were measured in the Southern Yellow Sea (SYS) and the East China Sea (ECS) in November 2007. The surface water CO concentrations in the investigated area ranged from 0.13 to 2.30 nmol L− 1, with an average of 0.68 nmol L− 1. Vertical profiles showed that CO concentrations declined with depth, with the maximum values appearing in the surface water (0–1 m). The diurnal variations of seawater CO concentrations were investigated at two anchor stations and the results showed that CO concentrations varied by a factor of 6–8 in the diurnal cycle, with maximum values appearing in the surface water (0–1 m). Atmospheric CO mixing ratios varied from 165 to 671 ppbv, with an average of 297 ppbv; these ratios decreased from 380 to 253 ppbv in the seaward direction and increased from 239 to 345 ppbv from south to north in the studied areas. Undersaturation was observed at eight of the 55 stations measured (15%) and the saturation factors ranged from 0.58 to 15.42, with an average of 3.34 ± 2.95. The sea-to-air fluxes of CO in the SYS and the ECS ranged from 0.50 to 4.20 μmol m− 2 d− 1, with an average of 1.82 ± 1.43 μmol m− 2 d− 1. In the incubation experiments, the microbial CO consumption rate constants in the surface water (Kco) ranged from 0.15 to 2.14 h− 1. A negative correlation between Kco and salinity was observed in the present study.