Global change is predicted to have a marked impact on freshwater ecosystems in the High Arctic, including temperature increase, enhanced precipitation, permafrost degradation and increased vegetation cover. These changes in river catchments can alter flow regime, solute transport to streams and substantially affect stream ecosystem functioning. The objective of this study was to evaluate changes in stream functioning in a high-Arctic stream in relation to changes in discharge, and runoff flow path. We measured environmental factors, biofilm structure, nutrient uptake rates and metabolism. We studied three reaches in a headwater stream in NE Greenland with different catchment characteristics in early and late summer (during two different years) to evaluate the potential influence of environmental change on Arctic stream ecosystem functioning. Highest nutrient uptake, primary production and ecosystem respiration was found in late summer showing that streams are more efficient at retaining nutrients and have higher autotrophic production, likely due to less impact of snowmelt, and lower discharge increasing the surface to volume ratio between streambed and water column. Nutrient uptake rates in late summer from high-Arctic tundra streams were comparable to uptake rates in temperate pristine streams, likely due to no shading by bank vegetation and longer days in the high-Arctic summer compared to temperate streams. Overall, the results of this study aids in the endeavor of predicting how climate-derived changes will affect in-stream nutrient uptake and metabolism in high-Arctic streams. The results suggest that their capacity to transport, cycle and retain carbon and nutrient may increase if the importance of soil water flow paths for streams also increase, thus with effect to stream trophic relations and solute export to coastal areas.

中文翻译：

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水文变化影响高北极河流中的河流养分吸收和初级生产

预计全球变化将对高北极地区的淡水生态系统产生显着影响，包括温度升高、降水增加、永久冻土退化和植被覆盖增加。河流集水区的这些变化会改变流态、溶质向溪流的运输，并显着影响溪流生态系统的功能。本研究的目的是评估与排放和径流路径变化相关的高北极河流中河流功能的变化。我们测量了环境因素、生物膜结构、养分吸收率和新陈代谢。我们在夏初和夏末（两个不同年份）研究了格陵兰东北部一条具有不同集水特征的上游河流中的三个河段，以评估环境变化对北极河流生态系统功能的潜在影响。在夏末发现最高的养分吸收、初级生产和生态系统呼吸，表明溪流在保留养分方面更有效，自养生产更高，这可能是由于融雪的影响较小，而排放量较低，增加了河床和水之间的表面积与体积比柱子。夏末高北极苔原溪流的养分吸收率与温带原始溪流的吸收率相当，这可能是因为与温带溪流相比，高北极夏季没有河岸植被的遮荫和更长的天数。总体而言，这项研究的结果有助于预测气候衍生的变化将如何影响高北极河流中的河流养分吸收和代谢。结果表明，它们的运输能力，