The sediment trap study clearly unraveled that the distinct peaks of C. davisiana fluxes occurred during summer to autumn in both the Okhotsk Sea and the northwestern North Pacific. The production of C. davisiana is closely related to the microbial production in the intermediate water. In the Okhotsk Sea, the distinct microbial biomass in the intermediate water, which is associated with the seasonal sea-ice rejected brine water during winter, may support the high C. davisiana abundance. Therefore, the significantly high C. davisiana abundance during the Last Glacial Maximum (LGM) in the high latitude open oceans implies the distinct microbial biomass in the intermediate water caused by the seasonal sea-ice coverage analogous to the present Okhotsk Sea.