Over the past 30 plus years, the Arctic has warmed at a rate of 0.6°C per decade. This has resulted in considerable permafrost thaw and alterations of hydrological and biogeochemical processes. Coincident with these changes, recent studies document increases in annual fluxes of inorganic nutrients in larger Arctic rivers. Changing nutrient fluxes in Arctic rivers have been largely attributed to warming‐induced active layer expansion and newly exposed subsurface source areas. However, the ability of Arctic headwater streams to modulate inorganic nutrient patterns manifested in larger rivers remains unresolved. We evaluated environmental conditions, stream ecosystem metabolism, and nutrient uptake in three headwater streams of the Alaskan Arctic to quantify patterns of retention of inorganic nitrogen (N) and phosphorous (P). We observed elevated ambient nitrate‐N (NO₃‐N) concentrations in late summer/early fall in two of three experimental stream reaches. We observed detectable increases in uptake as a result of nutrient addition in 88% of PO₄‐P additions (n = 25), 38% of NH₄‐N additions (n = 24), and 24% of NO₃‐N additions (n = 25). We observed statistically significant relationships between NH₄‐N uptake and ecosystem respiration, and PO₄‐P uptake and gross primary productivity. Although these headwater streams demonstrate ability to control downstream transport of PO₄‐P, we observed little evidence the same holds for dissolved inorganic N. Consequently, our results suggest that continued increases in terrestrial to aquatic N transfer in Arctic headwater landscapes are likely to be evident in larger Arctic rivers, in‐network lakes, and coastal environments.

中文翻译：

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阿拉斯加布鲁克斯山脉北麓的北极上游水流中河内营养物浓度和吸收的季节性

在过去的30多年中，北极以每十年0.6°C的速度变暖。这导致大量的多年冻土融化，并改变了水文和生物地球化学过程。与这些变化相吻合的是，最近的研究表明，在较大的北极河流中，无机养分的年通量增加了。北极河流中养分通量的变化主要归因于变暖引起的活动层扩张和新近暴露的地下源区。但是，北极上游水流调节较大河流中表现出的无机养分模式的能力仍未得到解决。我们评估了阿拉斯加北极地区三条上游水流的环境条件，河流生态系统代谢和养分吸收状况，以量化无机氮（N）和磷（P）的保留模式。₃个实验溪流中有2个在夏末/初降_3– N）浓度。我们观察到88％的PO ₄ -P添加物（n  = 25），38％的NH ₄ -N添加物（n  = 24）和24％的NO ₃ -N添加营养物导致摄入量增加（n  = 25）。我们观察到NH ₄ -N吸收和生态系统呼吸，PO ₄ -P吸收和总初级生产力之间存在统计学上的显着关系。尽管这些源头水流显示出控制PO ₄下游传输的能力‐P，我们几乎没有证据表明溶解的无机氮也是如此。因此，我们的结果表明，在北极较大的河流，网内湖泊和沿海地区，北极源头景观中陆地向水体氮的转移持续增加是很明显的。环境。