1. Climate change poses a significant threat to Arctic freshwater biodiversity, but impacts depend upon the strength of organism response to climate-related drivers. Currently, there is insufficient knowledge about Arctic freshwater biodiversity patterns to guide assessment, prediction, and management of biodiversity change.
2. As part of the Circumpolar Biodiversity Monitoring Program's first freshwater assessment, we evaluated diversity of diatoms, benthic macroinvertebrates, and fish in North American Arctic rivers. Alpha diversity was assessed in relation to temperature, water chemistry, bedrock geology, and glaciation history to identify important environmental correlates. Biotic composition was compared among groups to evaluate response to environmental gradients.
3. Macroinvertebrate α-diversity declined strongly with increasing latitude from 48°N to 82°N, whereas diatom and fish diversity peaked around 70°N without a clear latitudinal decline. Macroinvertebrate diversity was significantly positively related to air temperature. Diatom diversity was related to bedrock geology and temperature, whereas fish diversity was related to glaciation history.
4. Fish and macroinvertebrate assemblages differed between sites in western Canada, where invertebrate composition was more variable, and Alaska, where fish composition was more variable. In sites with both diatom and macroinvertebrate data, diatom composition was distinct in Alaska, where richness was highest in former glacial refugia. Macroinvertebrate composition was distinct in lowest-latitude eastern and high-latitude western Canadian sites where temperature was highest.
5. Temperature, precipitation, geology, calcium, and substrate size were important environmental correlates for diatoms and macroinvertebrates, although the relative importance of each correlate differed. Diatom taxa were most strongly associated with water chemistry, whereas benthic invertebrate composition related most strongly to precipitation and temperature.
6. This large-scale study provides the most substantial integration and analysis of river diatom, macroinvertebrate, and fish data from the North American Arctic to date. Findings suggest that macroinvertebrates will show the strongest response to climate-related shifts in temperature, whereas diatoms and fish are more likely to respond to climate-induced shifts in nutrients and hydraulic connectivity. However, significant gaps in data coverage limited our ability to reliably evaluate spatial patterns and detect change. These gaps could be reduced by improving collaborative efforts between the U.S.A. and Canada to harmonise future monitoring.

中文翻译：

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硅藻、底栖大型无脊椎动物和鱼类的多样性因北美北极河流的不同环境相关性而异

1. 气候变化对北极淡水生物多样性构成重大威胁，但影响取决于生物体对气候相关驱动因素的反应强度。目前，关于北极淡水生物多样性模式的知识不足，无法指导对生物多样性变化的评估、预测和管理。
2. 作为环极地生物多样性监测计划首次淡水评估的一部分，我们评估了北美北极河流中硅藻、底栖大型无脊椎动物和鱼类的多样性。评估了与温度、水化学、基岩地质和冰川历史相关的 Alpha 多样性，以确定重要的环境相关性。比较组间的生物成分以评估对环境梯度的反应。
3. 随着纬度从 48°N 增加到 82°N，大型无脊椎动物 α 多样性急剧下降，而硅藻和鱼类多样性在 70°N 左右达到峰值，但没有明显的纬度下降。大型无脊椎动物多样性与气温显着正相关。硅藻多样性与基岩地质和温度有关，而鱼类多样性与冰川历史有关。
4. 加拿大西部地区的鱼类和大型无脊椎动物群落不同，那里的无脊椎动物组成更加多变，而阿拉斯加的鱼类成分更加多变。在同时拥有硅藻和大型无脊椎动物数据的地点，阿拉斯加的硅藻成分明显不同，前冰川避难所的丰富度最高。在温度最高的加拿大东部最低纬度和西部高纬度地区，大型无脊椎动物组成不同。
5. 温度、降水、地质、钙和底物大小是硅藻和大型无脊椎动物的重要环境相关因素，尽管每个相关因素的相对重要性不同。硅藻类群与水化学的关系最为密切，而底栖无脊椎动物的组成与降水和温度的关系最为密切。
6. 这项大规模研究提供了迄今为止对来自北美北极地区的河流硅藻、大型无脊椎动物和鱼类数据的最实质性的整合和分析。研究结果表明，大型无脊椎动物将对气候相关的温度变化表现出最强的反应，而硅藻和鱼类更有可能对气候引起的营养物质和水力连通性变化作出反应。然而，数据覆盖范围的巨大差距限制了我们可靠地评估空间模式和检测变化的能力。这些差距可以通过改善美国和加拿大之间的合作努力来协调未来的监测。