Molecular biogeography of planktonic and benthic diatoms in the Yangtze River

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.

Sedimentary microeukaryotes reveal more dispersal limitation and form networks with less connectivity than planktonic microeukaryotes in a highly regulated river

“…The similar distribution patterns between planktonic and benthic diatoms have also been recently reported by Wang et al. (2019) in the Yangtze River. This may be ascribed to the interaction between planktonic and benthic diatoms, meaning that phytoplankton can be derived from benthic diatoms, and sinking planktonic algae can accumulate in sediments and become benthic algae (Tekwani et al., 2013).…”

“…In this study, damming significantly reduced the relative abundance of both planktonic and benthic diatoms, implying a potential effect of damming on diatom‐mediated biogeochemical cycling of primary elements such as C, N, P, and Si in river ecosystem. On the one hand, changes in water level in dam‐formed reservoirs make the sediments become a habitat with limited light, which are unsuitable for benthic diatoms to thrive (Wang et al., 2019). On the other hand, the deepened river channel due to damming can also reduce the interaction of planktonic and benthic diatoms and their migration rate.…”

Comammox Nitrospira within the Yangtze River continuum: community, biogeography, and ecological drivers

“…Artificial damming splits the river channel into separate reaches and alters the microbial ecology immediately upstream and downstream [ 25 – 27 ]. The TGD, as one of the world’s largest dams, had a profound influence on the spatial succession of comammox Nitrospira and canonical AOPs in sediments.…”

“…In July 2017, additional synchronous sampling was implemented at three national hydrologic sites Tuotuohe (TTH), Tongtianhe (TOTH) and Zhimenda (ZMD) in the source region of the Yangtze River located on the Qinghai-Tibetan Plateau. Considering insignificant interannual variations in water quality, riverine habitats and aquatic organisms on the Qinghai-Tibetan Plateau in recent years [ 24 , 25 ], the above remedial sampling was helpful for obtaining a complete biogeographic pattern of comammox Nitrospira throughout the whole river. Details of the sampling were provided in our previous work [ 25 – 27 ].…”

“…Considering insignificant interannual variations in water quality, riverine habitats and aquatic organisms on the Qinghai-Tibetan Plateau in recent years [ 24 , 25 ], the above remedial sampling was helpful for obtaining a complete biogeographic pattern of comammox Nitrospira throughout the whole river. Details of the sampling were provided in our previous work [ 25 – 27 ]. Spatial and environmental parameters at each site were measured and are summarized in the Supplementary Information .…”