Abstract
To date, few aquatic microbial ecology studies have discussed the variability of the microbial community in exorheic river ecosystems on both the spatial and seasonal scales. In this study, we examined the spatio-temporal variation of bacterioplankton community composition in an anthropogenically influenced exorheic river, the Haihe River in Tianjin, China, using pyrosequencing analysis of 16S rRNA genes. It was verified by one-way ANOVA that the spatial variability of the bacterioplankton community composition over the whole river was stronger than the seasonal variation. Salinity was a major factor leading to spatial differentiation of the microbial community structure into riverine and estuarial parts. A high temperature influence on the seasonal bacterial community variation was only apparent within certain kinds of environments (e.g., the riverine part). Bacterial community richness and diversity both exhibited significant spatial changes, and their seasonal variations were completely different in the two environments studied here. Furthermore, riverine bacterial community assemblages were subdivided into urban and rural groups due to changes in the nutritional state of the river. In addition, the nutrient-loving group including Limnohabitans, Hydrogenophaga, and Polynucleobacter were abundant in the urbanized Haihe River, indicating the environmental factors in these anthropogenic waterbodies heavily influence the core freshwater community composition.
Highlights
Microbial communities are key components in aquatic ecosystems and are among the most important players in biogeochemical cycling of fundamental elements (Azam and Worden, 2004)
Principal component analysis (PCA) of the entire data set revealed three PCs with eigenvalues of >1 that explained about 79.0% of the total variance in the environmental data set
The first PC accounting for 40.8% of the total variance was correlated with total nitrogen (TN), total phosphorus (TP), and DTP, which represents the trophic state of the river
Summary
Microbial communities are key components in aquatic ecosystems and are among the most important players in biogeochemical cycling of fundamental elements (Azam and Worden, 2004). Spatial and temporal variations in a bacterioplankton community may often be attributed to a response to environmental changes Factors such as water temperature (Crump and Hobbie, 2005; Kan et al, 2007), lake retention time (Lindström et al, 2005), salt concentration (Zhang et al, 2012), phytoplankton succession (Pinhassi et al, 2004; Niu et al, 2011), and the biomass of grazers on bacterioplankon (Lindström, 2000) have been suggested to be related to the bacterial community composition. Obvious temperature effects were found in other aquatic ecosystems such as lakes (Shade et al, 2007; Lymer et al, 2008), estuarine, and coastal waters (Jing and Liu, 2012), which suggests a potential climate influence on the seasonal pattern of bacterial succession (Crump and Hobbie, 2005; Kent et al, 2007)
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