We examined primary production (PP) and the assimilation rates of nitrate (ρNO₃^-), ammonium (ρNH₄⁺) and dinitrogen (ρN₂) using ¹³C and ¹⁵N tracer techniques along bay to offshore transects in the Oyashio-Kuroshio-Tsugaru Warm Current interfrontal region in the northwestern North Pacific Ocean, during five research cruises covering a full seasonal cycle. Surface inorganic N was depleted in the bays and the offshore region from summer to fall, but the higher particulate organic carbon (POC)/particulate nitrogen (PN) ratio and higher maximum N assimilation rate observed kinetics experiments in the bays suggest that N limitation was stronger in bays than offshore. PP (295–19,200 nmol C L⁻¹ d⁻¹), ρNO₃^- (9.45–650 nmol N L⁻¹ d⁻¹) and ρNH₄⁺ (11.6–494 nmol N L⁻¹ d⁻¹) in the surface waters were generally low in summer and high in spring. Different from the cases of ρNO₃^- and ρNH₄⁺, ρN₂ was high (up to 12 nmol N L⁻¹ d⁻¹) in mid-summer, especially in offshore regions, and moderate or low (≤2.26 nmol N L⁻¹ d⁻¹) during other seasons. N₂ fixation largely contributed to total new production (up to 29%) in mid-summer. The mean f-ratio, estimated as the ratio of (ρNO₃^- + ρN₂) to (ρNO₃^- + ρN₂ + ρNH₄⁺) at two offshore stations varied within the range of 0.29–0.83 (mean 0.54 ± 0.20). Comparison of the PP and total N assimilation (ρNO₃^- + ρN₂ + ρNH₄⁺) indicated that the ratio of C to N assimilation rates (max. 95) far exceeded the Redfield ratio (6.6). This finding suggests that other sources of N (e.g., dissolved organic nitrogen) contributed significantly to total N assimilation; if this is correct, the estimated f-ratio may be too high. Alternatively, the f_C-ratio was estimated from the ratio of (ρNO₃^- + ρN₂) to PP by assuming the Redfieldian assimilation ratio, and it ranged from 0.06 to 1.10 (mean 0.45 ± 0.31). Despite uncertainties in both the f- and f_C-ratio estimation, our data provide evidence that a large fraction of PP is potentially available for export to deep waters and to higher trophic levels in the interfrontal region of the western North Pacific.

我们检查了初级生产（PP）和硝酸盐的同化率（ρNO ₃ ^- ），铵（ρNH ₄ ⁺）和一氧化二（ρN ₂使用）¹³ C和¹⁵在北太平洋西北部的Oyashio-Kuroshio-Tsugaru暖流当前的额际区域中，从海湾到近海样带的N示踪技术，涵盖了整个季节周期的五次研究航行期间。从夏季到秋季，海湾和近海区域的表面无机N都被消耗掉了，但是在海湾中观察到的动力学实验表明，较高的颗粒有机碳（POC）/颗粒氮（PN）比和较高的最大N同化率表明氮限制是海湾比海上强。PP（295-19,200纳摩尔CL ^-1 d ^-1），ρNO ₃ ^-（9.45-650纳摩尔NL ^-1 d ^-1）和ρNH ₄ ⁺（11.6-494纳摩尔NL ^-1 d地表水中的^-1）通常在夏季低，而在春季高。从ρNO的情况下不同的₃ ^-和ρNH ₄ ⁺，ρN ₂高（可达12纳摩尔NL ^-1 d ^-1）在盛夏，特别是在近海区域，以及中度或低（≤2.26纳摩尔NL ^-1 d ^-1）在其他季节。N ₂固定在仲夏期间对新总产量的贡献很大（高达29％）。平均˚F -ratio，估计为（ρNO比例₃ ^-  +ρN ₂）至（ρNO ₃ ^-  +ρN ₂  +ρNH两个离岸站的₄ ⁺）在0.29–0.83（平均0.54±0.20）范围内变化。PP和总氮同化的比较（ρNO ₃ ^-  +ρN ₂  +ρNH ₄ ⁺）表示的C到N同化率（最大95）的比率远远超过Redfield的比率（6.6）。这一发现表明，其他氮源（例如溶解的有机氮）对总氮的吸收有显着贡献。如果这是正确的，则估计的f比率可能太高。可替代地，˚F _Ç -ratio从之比（ρNO估计₃ ^-  +ρN ₂）假设为Redfieldian同化比，则PP范围为0.06至1.10（平均0.45±0.31）。尽管f和f _C比率的估计都不确定，但我们的数据提供了证据，表明有很大一部分PP可以用于出口到北太平洋西部前缘地区的深水区和较高的营养水平。