Nutrients Drive the Structures of Bacterial Communities in Sediments and Surface Waters in the River-Lake System of Poyang Lake

Ze Ren,Yang Yu,Min Zhang,Xiaodong Qu,Wenqi Peng

doi:10.3390/w11050930

Abstract

Lake and its inflow rivers compose a highly linked river-lake system, within which sediment and water are also closely connected. However, our understanding of this linked and interactive system remains unclear. In this study, we examined bacterial communities in the sediments and surface waters in Poyang Lake and its five tributaries. Bacterial communities were determined while using high-throughput 16S rRNA gene sequencing. The results showed significant differences of bacterial communities between sediments and surface waters, as well as between Poyang lake and its tributaries, suggesting that the river-lake system of Poyang Lake provides diverse and distinct habitats for bacterial communities, including lake water, lake sediment, river water, and river sediment. These biomes harbor distinct bacterial assemblages. Sediments harbor more diverse bacterial taxa than surface waters, but the bacterial communities in surface waters were more different across this river-lake system than those in sediments. In this eutrophic river-lake ecosystem, nitrogen and phosphorus were important drivers in sediment bacterial communities. Nitrogen, phosphorus, and dissolved organic carbon, as well as their stoichiometric ratios affected bacterial communities in surface waters. Moreover, network analysis revealed that the bacterial communities in surface waters were more vulnerable to various disturbances than in sediments, due to lower alpha diversity, high complexity of network, and a small number of key taxa (module hubs and connectors). Nutrient variables had strong influences on individual operational taxonomic units (OTUs) in the network, especially in bacterial network in surface waters. Different groups of taxa responded differently to nutrients, with some modules being more susceptible to nutrient variations. This study increased our current knowledge of linked river-lake ecosystems and provided valuable understanding for effective management and protection of these ecosystems by revealing bacterial communities in sediments and surface waters in Poyang Lake and its tributaries, as well as their responses to nutrients variation.

Highlights

Microorganisms encompass tremendous diversity [1] and exhibit high compositional and functional variability in freshwater environments [2]
The results showed that the bacterial networks in sediments and surface waters had non-random, scale-free, and “small world” properties, which are the structural characteristics of many microbial ecological networks [77,78]
Investigating bacterial communities that live in surface waters and sediments of the river-lake system of Poyang Lake is pivotal in understanding the structures and the diversity of this freshwater ecosystem

Summary

Introduction

Microorganisms encompass tremendous diversity [1] and exhibit high compositional and functional variability in freshwater environments [2]. Bacterial communities have a broad genetic diversity in the water body in lake ecosystems [2,3]. As a distinct realm of lake ecosystems, sediments host a tremendous diversity of microorganisms, which play vital roles in maintaining the benthic food web structure, as well as driving major biogeochemical cycles [4,5]. The metabolic activity of the bacterial community in sediments, such as nutrient store and release, methane production, and iron reduction, can drive the biogeochemical cycles and influence water quality [6,7]. Due to the different chemical and physical environment between water and sediment habitats, the processes driving the variation of bacterial communities are different in water and sediment environments [8]

Methods

Results

Discussion

Conclusion