Increased nutrient loading in aquatic environments can have a long‐lasting influence on ecosystem processes and functions. The Kootenai River was historically oligotrophic, but nitrate levels have been steadily increasing since the mid‐2000s, while phosphorus levels have remained low. Our study objective was to evaluate the current nutrient distribution throughout the Kootenai River watershed in the context of land use and land cover change. Each of the three land cover types we assessed, agriculture, developed areas, and surface mines, encompass less than 1% of the land area in the Kootenai River watershed. We measured nitrate, ammonium, and soluble reactive phosphorus (SRP) monthly at sites spanning 400 river km on the Kootenai River, and co‐located tributary sites in British Columbia, Canada, and Montana and Idaho, USA. During July 2017, we measured the same nutrients along each of the selected tributaries with co‐located sites at sub‐catchment tributaries. Sites were selected to include a range of contributing drainage areas identified as agricultural, developed, or mining. Nutrient concentrations ranged from 0.012 to 4.299 mg/L for nitrate, 0.0005–0.02 mg/L for ammonium, and 0.003–0.076 mg/L for SRP. Nitrate concentrations were elevated downstream of mining land cover, and decreased with distance from the mining areas; however, nitrate remained elevated compared to sites not affected by mining activity. If the imbalance of N:P continues to increase due to nitrate loading, resources available to biota may become skewed, resulting in alterations to ecosystem processes and functions critical to support the biodiversity in the Kootenai River.

中文翻译：

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跨界Kootenai流域的土地覆盖变化很小，极大地改变了水质

在水生环境中增加的养分含量会对生态系统的过程和功能产生长期的影响。Kootenai河历来是贫营养的，但是自2000年代中期以来，硝酸盐水平一直在稳步上升，而磷水平却一直很低。我们的研究目标是在土地利用和土地覆被变化的背景下评估整个Kootenai河流域的当前养分分布。我们评估的三种土地覆被类型，农业，发达地区和露天矿都分别占库特奈河流域土地面积的不到1％。我们每月在Kootenai河上400公里公里的站点以及加拿大不列颠哥伦比亚省，美国蒙大拿州和爱达荷州的同一地点的支流站点每月测量硝酸盐，铵和可溶性反应性磷（SRP）。在2017年7月，我们测量了每个选定支流的相同养分，并在子汇水支流的同一地点进行了测量。选择的地点包括一系列确定为农业，发达或采矿的重要流域。营养盐的硝酸盐浓度范围为0.012至4.299 mg / L，铵盐的浓度范围为0.0005-0.02 mg / L，SRP的浓度范围为0.003-0.076 mg / L。硝酸盐浓度在采矿土地覆被的下游升高，并随距采矿区的距离而降低；然而，与不受采矿活动影响的地点相比，硝酸盐仍保持较高的水平。如果由于硝酸盐负荷导致N：P的不平衡继续加剧，则可用于生物群的资源可能会倾斜，从而导致生态系统过程和功能的改变，这对于支持Kootenai河的生物多样性至关重要。