To quantify the biological carbon pump in the Northwestern Pacific and project future changes induced by multiple stressors, a comparative biogeochemistry study of subarctic-eutrophic and subtropical-oligotrophic regions, the K2S1 project, was conducted between 2010 and 2014. The present study uses data collected during the K2S1 project to re-examine the biological carbon pump in subarctic and subtropical regions of the northwestern Pacific with a focus on the factors governing the attenuation of the downward fluxes of particulate organic carbon (POC). Seasonal and time-series observations made during the K2S1 project revealed that primary productivity and the POC flux in the upper 200 m at subtropical-oligotrophic station S1 were comparable to or slightly higher than those at subarctic-eutrophic station K2, but the POC flux at a depth of ∼5000 m at K2 was 2–3 times that at S1. Based on these observations, the index of vertical attenuation (exponent b of the “Martin curve”) was estimated to be 0.64 at K2 and 0.90 at S1. The downward transport of POC was therefore more efficient at the subarctic station than at the subtropical station. Sinking particles were ballasted mainly by biogenic opal (Opal) at K2 and by CaCO₃ at S1. The results of a multiple linear regression analysis of sediment trap data indicated that among potential ballast materials, Opal was most strongly correlated with POC at K2. Thus, Opal might contribute to the more effective vertical transport of POC in the western North Pacific Subarctic region. In addition, lower water temperatures and dissolved oxygen concentrations in the twilight zone (200–1000 m depth) at K2 likely slowed microbial decomposition of organic carbon and may also have contributed to the smaller attenuation of the downward POC flux. However, seasonal observations indicated that the carbon demand of zooplankton (prokaryotes) in the water column at K2 was ∼2.5 (1.5) times that at S1. These results were inconsistent with the lower rate of attenuation of POC fluxes at K2. Moreover, the carbon demand at the two stations inferred from the POC fluxes and the carbon fluxes associated with diurnal migration by zooplankton exceeded the carbon supply, especially at K2. Other sources of carbon, such as slowly sinking and suspended POC, might account for this mismatch.

为了量化西北太平洋的生物碳泵，并预测多种压力源引起的未来变化，在2010年至2014年之间进行了南亚富营养化地区和亚热带富营养化地区K2S1项目的比较生物地球化学研究。本研究使用收集的数据在K2S1项目中，对西北太平洋亚北极和亚热带地区的生物碳泵进行了重新检查，重点是控制颗粒状有机碳（POC）向下通量衰减的因素。在K2S1项目期间进行的季节和时间序列观测表明，亚热带-贫营养站S1的上部200 m的初级生产力和POC通量与亚营养不足的富营养站K2相当或略高，但是在K2处约5000 m深度的POC通量是S1处的2-3倍。基于这些观察，垂直衰减指数（指数b“ Martin曲线”的平均值估计在K2为0.64，在S1为0.90。因此，在亚北极站上，POC的向下输送比在亚热带站上更为有效。下沉颗粒主要由生物蛋白石（蛋白石）在K2和CaCO _3压载在S1。沉积物陷阱数据的多元线性回归分析结果表明，在潜在的压载材料中，蛋白石与K2处的POC密切相关。因此，蛋白石可能有助于西北太平洋亚北极地区POC的更有效的垂直运输。此外，较低的水温和K2处暮光区（深度200-1000 m）的溶解氧浓度可能会减慢微生物对有机碳的分解，也可能会降低POC向下通量的衰减。然而，季节性观测表明，在K2处水柱中浮游动物（原核生物）的碳需求是在S1处的约2.5倍（1.5）倍。这些结果与K2处POC通量的较低衰减率不一致。此外，从POC通量推断的两个站点的碳需求以及与浮游动物昼间迁移相关的碳通量超过了碳供应，尤其是在K2处。其他碳源，例如缓慢下沉和悬浮的POC，可能是造成这种不匹配的原因。