BACKGROUND Diatoms are of great significance to primary productivity in oceans, yet little is known about their biogeographic distribution in oligotrophic rivers. RESULTS With the help of metabarcoding analysis of 279 samples from the Yangtze River, we provided the first integral biogeographic pattern of planktonic and benthic diatoms over a 6030 km continuum along the world's third largest river. Our study revealed spatial dissimilarity of diatoms under varying landforms, including plateau, mountain, foothill, basin, foothill-mountain, and plain regions, from the river source to the estuary. Environmental drivers of diatom communities were interpreted in terms of photosynthetically active radiation, temperature, channel slope and nutrients, and human interference. Typical benthic diatoms, such as Pinnularia, Paralia, and Aulacoseira, experienced considerable reduction in relative abundance downstream of the Three Gorges Dam and the Xiluodu Dam, two of the world's largest dams. CONCLUSIONS Our study revealed that benthic diatoms are of particular significance in characterizing motile guild in riverine environments, which provides insights into diatom biogeography and biogeochemical cycles in large river ecosystems.

中文翻译：

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长江中浮游和底栖硅藻的分子生物地理学。

背景技术硅藻对于海洋的初级生产力具有重要意义，但是关于它们在贫营养河流中的生物地理分布知之甚少。结果借助对长江中279个样品的元条形码分析，我们在世界第三大河沿岸6030公里的连续区内，提供了浮游和底栖硅藻的第一个完整生物地理格局。我们的研究表明，从河源到河口，硅藻在不同地形（包括高原，山区，山麓，盆地，山麓山和平原地区）下的空间差异。硅藻群落的环境驱动因素根据光合有效辐射，温度，通道斜率和养分以及人为干扰进行了解释。典型的底栖硅藻，例如Pinnularia，Paralia和Aulacoseira，世界上最大的两个水坝三峡大坝和溪洛渡大坝下游的相对丰度大大降低。结论我们的研究表明，底栖硅藻对于表征河流环境中的运动行会具有特别重要的意义，它为了解大型河流生态系统中的硅藻生物地理学和生物地球化学循环提供了见识。