Abstract
BackgroundDiatoms are of great significance to primary productivity in oceans, yet little is known about their biogeographic distribution in oligotrophic rivers.ResultsWith 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.ConclusionsOur 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.
Highlights
Diatoms are of great significance to primary productivity in oceans, yet little is known about their biogeographic distribution in oligotrophic rivers
Alpha and beta diversity of diatom communities Molecular barcoding based on high-throughput sequencing (HTS) provided a detailed diatom directory for the whole Yangtze River at different taxonomy levels, i.e., 4 classes, 37 orders, 60 families, and 152 genera
Since diatoms were reported to predominate in phytoplankton at high nitrogen to phosphorus ratio (N:P > 16) in water [40], we investigated the response of planktonic and benthic diatoms to total nitrogen (TN):total phosphorus (TP) in the Yangtze River
Summary
Diatoms are of great significance to primary productivity in oceans, yet little is known about their biogeographic distribution in oligotrophic rivers. Diatoms are ubiquitous and diverse species of single-celled, eukaryotic, photosynthetic microorganisms [3], and are often the dominant primary producers in marine and freshwater ecosystems [4]. Diatoms in such ecosystems may be remarkably dissimilar either in phylogenetic composition or biogeographic distribution [5, 6]. Malviya et al [13] provided a new estimate of diversity and distribution of marine planktonic diatoms based on the V9 region of eukaryotic 18S rDNA. The V4 region of 18S rDNA was proposed for diatom barcoding in studies of diatoms in river and deltaic systems [9, 12]
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