Taxonomic and Functional Differences between Microbial Communities in Qinghai Lake and Its Input Streams.

James J Elser,Xiaodong Qu,Fang Wang,Limin Chu,Yang Liu,Ze Ren

doi:10.3389/fmicb.2017.02319

Abstract

Understanding microbial communities in terms of taxon and function is essential to decipher the biogeochemical cycling in aquatic ecosystems. Lakes and their input streams are highly linked. However, the differences between microbial assemblages in streams and lakes are still unclear. In this study, we conducted an intensive field sampling of microbial communities from lake water and stream biofilms in the Qinghai Lake watershed, the largest lake in China. We determined bacterial communities using high-throughput 16S rRNA gene sequencing and predicted functional profiles using PICRUSt to determine the taxonomic and functional differences between microbial communities in stream biofilms and lake water. The results showed that stream biofilms and lake water harbored distinct microbial communities. The microbial communities were different taxonomically and functionally between stream and lake. Moreover, streams biofilms had a microbial network with higher connectivity and modularity than lake water. Functional beta diversity was strongly correlated with taxonomic beta diversity in both the stream and lake microbial communities. Lake microbial assemblages displayed greater predicted metabolic potentials of many metabolism pathways while the microbial assemblages in stream biofilms were more abundant in xenobiotic biodegradation and metabolism and lipid metabolism. Furthermore, lake microbial assemblages had stronger predicted metabolic potentials in amino acid metabolism, carbon fixation, and photosynthesis while stream microbial assemblages were higher in carbohydrate metabolism, oxidative phosphorylation, and nitrogen metabolism. This study adds to our knowledge of stream-lake linkages from the functional and taxonomic composition of microbial assemblages.

Highlights

Microbial communities are fundamental components in aquatic environments and play a crucial role in driving global energy fluxes and biogeochemical cycling (Falkowski et al, 2008)
Previous research about the microbial communities in Qinghai Lake mainly focused on lake itself, including the microbial communities in lake water column (Huang et al, 2014), water-sediment interface (Dong et al, 2006), and sediment (Jiang et al, 2009)
There were no significant correlations between physicochemical environment dissimilarities and functional dissimilarities (Mantel test, P > 0.05). These results suggest that, in stream biofilms and lake water, the overall functional differences between the microbial communities were significantly correlated with the differences of community composition

Summary

Introduction

Microbial communities are fundamental components in aquatic environments and play a crucial role in driving global energy fluxes and biogeochemical cycling (Falkowski et al, 2008). A majority of microorganisms occur in benthic biofilms (Findlay, 2010), where they play a key role in biogeochemical cycling and are responsible for organic matter (OM) mineralization, nutrient uptake, the transfer of nutrients to higher trophic levels, as well as immobilization and transformation of contaminants (Schiller et al, 2007; Buchkowski et al, 2015). Microbial communities have an extremely high level of genetic diversity and play a key role in biogeochemical cycles (Newton et al, 2011; Hayden and Beman, 2016; Huang et al, 2016). Taxonomic and functional changes of microbial communities in stream biofilms and lake water may contribute to changes in ecosystem processes (Ylla et al, 2014; Wilhelm et al, 2015; Zwirglmaier et al, 2015; Peter and Sommaruga, 2016)

Methods

Results

Conclusion