Characterization of the bacterioplankton community and the influencing factors in the upper reaches of the Han River basin.

He Sun,Xiaoming Jiang,Haoran He,Hao Wang,Gengnan Zhao,Xu Han,Baozhu Pan

doi:10.1007/s11356-021-14906-2

Abstract

The upper reaches of the Han River are the source region of water for the Middle Route of China's South-to-North Water Diversion Project, mainly for household, industrial, and irrigation purposes. Planktonic bacteria are more sensitive than macroorganisms to water physical and chemical properties and play a critical role in biogeochemical processes in river ecosystems. In November 2017 and April 2018, a systematic and methodical survey was carried out to evaluate the water quality and bacterial communities, on the mainstem of the Han River and its five main tributaries. In this study, high-throughput sequencing technology has been employed to investigate the bacterioplankton community composition. The results indicated the following: (1) diversity increased downstream, especially in the upper reaches of the Han River. (2) The relative abundance of Actinobacteria increased with the increase of river length, while that of Bacteroidetes decreased slightly. (3) Five tributaries were found to be importance sources of taxa to the Han River; however, in both months, a large proportion of operational taxonomic units (37.84% and 36.34%, respectively) had unknown sources. (4) Finally, redundancy analysis (RDA) and Bioenv analysis showed that environmental parameters (pH, TN, Cond, NH4+-N, DO, NO2--N, Chl-a, and T) had a great influence (p ≤ 0.05) on the bacterioplankton community. These research results are beneficial for the managing the ecological system, protecting the tributary biodiversity, and conserving the mainstem and tributaries of the Han River basin.

Highlights

Rivers are the main source of industrial, agricultural, and domestic water for humans, linking the water cycle and the recycling of carbon, nitrogen and phosphorus (Schultz et al 2013, Adhikari et al 2019)
It is reported that Proteobacteria, Bacteroidetes and Actinobacteria are three of the most abundant phyla in rivers (Wang et al 2017, Liu et al 2018)
There was no similar pattern of Actinobacteria abundance in the tributaries

Summary

Introduction

Rivers are the main source of industrial, agricultural, and domestic water for humans, linking the water cycle and the recycling of carbon, nitrogen and phosphorus (Schultz et al 2013, Adhikari et al 2019). Among the critical components of river ecosystems, microbes play an important role in degrading the multi-resourced pollutants (Llirós et al 2014, Sorokin et al 2014). As an important producer and decomposer of aquatic ecosystems, bacterioplankton can remineralize elements making them available for primary producers (Wu et al 2015). The spatiotemporal variation of bacterioplankton composition has been demonstrated, which tends to have repeatable and predictable patterns in river ecosystems (Chen et al 2019). Temperature changes the abundance of various bacteria in the river by affecting the growth rate of the bacteria (Sieburth 1967) in the river and their motility (McCaulou et al 1995). Nutrients could affect the bacterial communities in water by changing its composition and distribution via the “bottom-up effect” (Pérez & Sommaruga 2006, Bouvy et al 2011). Bacteria can be influenced by the composition and abundance of predators (e.g., ciliates) (Nakano et al 1998)

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