Abstract
Microbes are key components of aquatic ecosystems and play crucial roles in global biogeochemical cycles. However, the spatiotemporal dynamics of planktonic microbial community composition in riverine ecosystems are still poorly understood. In this study, we used denaturing gradient gel electrophoresis of PCR-amplified 16S and 18S rRNA gene fragments and multivariate statistical methods to explore the spatiotemporal patterns and driving factors of planktonic bacterial and microbial eukaryotic communities in the subtropical Jiulong River, southeast China. Both bacterial and microbial eukaryotic communities varied significantly in time and were spatially structured according to upper stream, middle-lower stream and estuary. Among all the environmental factors measured, water temperature, conductivity, PO4-P and TN/TP were best related to the spatiotemporal distribution of bacterial community, while water temperature, conductivity, NOx-N and transparency were closest related to the variation of eukaryotic community. Variation partitioning, based on partial RDA, revealed that environmental factors played the most important roles in structuring the microbial assemblages by explaining 11.3% of bacterial variation and 17.5% of eukaryotic variation. However, pure spatial factors (6.5% for bacteria and 9.6% for eukaryotes) and temporal factors (3.3% for bacteria and 5.5% for eukaryotes) also explained some variation in microbial distribution, thus inherent spatial and temporal variation of microbial assemblages should be considered when assessing the impact of environmental factors on microbial communities.
Highlights
Microbes are mainly composed of bacteria, archaea, algae, protozoa, fungi and small metazoa, representing the most abundant and diverse group across ecosystems, and playing crucial roles in aquatic ecosystem functioning [1,2]
The concentrations of total nitrogen (TN), Total phosphorus (TP), PO4-P, TC and Total organic carbon (TOC) were significantly higher in the dry season than in the wet season
Variability was mainly explained by an increase in the TN/TP (r = 0.817, P < 0.01) and temperature (r = 0.793, P < 0.01) and a decrease in the PO4-P (r = –0.935, P < 0.01), TP (r = –0.935, P < 0.01), TOC (r = –0.807, P < 0.01) and TN (r = –0.715, P < 0.01)
Summary
Microbes are mainly composed of bacteria, archaea, algae, protozoa, fungi and small metazoa, representing the most abundant and diverse group across ecosystems, and playing crucial roles in aquatic ecosystem functioning [1,2]. Microbial communities are driven by many interacting factors and processes, and it has been shown that environmental factors play the most important role in shaping the composition of microbial communities [11,12,13]. Insufficient knowledge of microbial spatiotemporal variation can hinder the effective assessment of the relative importance of environmental factors in driving microbial community succession in structure and function [14]. Previous studies investigated microbial assemblages and their explanatory factors using variation partitioning and ordination procedures to partition the variation of species data into environmental and spatial components [15,16]. Environmental and spatial matrices) has been carried out frequently in previous studies (see [15,16]), to the best of our knowledge, few microbial community fingerprinting studies published so far used the third matrix containing temporal variables Partitioning in two independent matrices (eg. environmental and spatial matrices) has been carried out frequently in previous studies (see [15,16]), to the best of our knowledge, few microbial community fingerprinting studies published so far used the third matrix containing temporal variables
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