The Yukon River exports a large amount of dissolved organic carbon (DOC), much of which is colored, absorbing visible and ultraviolet light. Yukon River water typically has low total dissolved nitrogen (TDN), with an average DOC : TDN ratio of 21.1 (mol C mol N⁻¹) ~ 200 km upstream from the coast at Pilot Station, Alaska. TDN has been correlated to the bioavailability of DOC, but a direct estimate of the dependence of DOC reactivity on nutrient availability has not been conducted in the Yukon River delta. The biodegradability of DOC and colored dissolved organic matter (CDOM) was assessed along a gradient within the Yukon River delta and into the coastal ocean. Samples were dark incubated at 20°C and half of the incubations were amended with inorganic nutrients. At five time points through 27 d, CDOM absorption and DOC concentration were measured. Initial DOC concentration was 113–830 μmol C L⁻¹ and CDOM absorption at 443 nm (a443) ranged from 0.16 to 7.8 m⁻¹ from the ocean to a high CDOM lake. DOC was relatively unreactive, with 3–6% of DOC degrading in riverine samples and little difference between nutrient amended and control incubations. Control river delta a443 decreased 3–10%, while nutrient amended treatments saw a 6–22% decline over 27 d. In the nutrient amended riverine stations, CDOM absorption loss was greater at blue wavelengths and CDOM degradation was greater than total DOC loss. DOC was resistant to biodegradation in both nutrient amended and ambient conditions, while CDOM was preferentially degraded when nutrients were replete.

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养分充足条件下育空河三角洲有色溶解有机物的优先流失

育空河出口大量溶解的有机碳（DOC），其中大部分是彩色的，吸收可见光和紫外线。育空河水的总溶解氮（TDN）通常较低，平均DOC：TDN比为21.1（mol C mol N ^-1），距离阿拉斯加先导站海岸上游200公里。TDN与DOC的生物利用度相关，但是在育空河三角洲尚未对DOC反应性对养分利用的依赖性进行直接估算。DOC和有色溶解有机物（CDOM）的生物降解能力是在育空河三角洲内并进入沿海海洋的一个坡度进行评估的。将样品在20°C下黑暗孵育，然后将一半的孵育物用无机营养液修正。在至27 d的五个时间点，测量CDOM吸收和DOC浓度。初始DOC的浓度为113-830  μ摩尔C L ^-1和CDOM吸收在443纳米（A443）介于0.16至7.8米^-1从海洋到高CDOM湖。DOC相对没有反应性，河样品中DOC降解3–6％，而养分改良和对照培养之间几乎没有差异。对照河三角洲a443下降3–10％，而养分改良处理在27 d内下降6–22％。在经过营养素改良的河流站中，蓝色波长处的CDOM吸收损失更大，而CDOM的降解大于总DOC损失。DOC在修改的养分和环境条件下均抗生物降解，而养分充足时CDOM优先降解。