Taxon-Driven Functional Shifts Associated with Storm Flow in an Urban Stream Microbial Community

Abstract

Urban streams in various parts of the world are facing increased anthropogenic pressure on their water quality, and storm flow events represent one such source of complex physical, chemical, and biological perturbations. Microorganisms are important components of these streams from both ecological and public health perspectives. Analysis of the effect of perturbations on the stream microbial community can help improve current knowledge on the impact such chronic disturbances can have on these water resources. This study examines microbial community dynamics during rain-induced storm flow conditions in an urban stream of the Chicago Area Waterway System. Additionally, using shotgun metagenomics we identified significant shifts in the microbial community composition and functional gene content following a high-rainfall event, with potential environment and public health implications. Previous work in this area has focused on specific genes/organisms or has not assessed immediate storm flow impact.

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“…1) and composition (Table S1 , Fig. 3), similar to what we observed previously (Chaudhary et al 2018). The river samples had significantly higher alpha diversity (Shannon) than the effluent samples (nonparametric t-test p= 0.04).…”

“…Despite the fact that WWTP effluent accounts for ~70% of the river flow under base conditions in the system we studied, the river is still inhabited by many typical freshwater bacteria such as a variety of Actinobacteria including members of the ac1 clade of actinomycetes, freshwater Pelagibacter, and Polynucleobacter (Hahn et al 2011;Newton et al 2011;Oh et al 2011). We previously observed an increase in the relative abundance of numerous bacteria under stormflow conditions in this system, which coincided with more than double the flow of non-disinfected effluent from the WWTP (Chaudhary et al 2018). Freshwater bacteria made up a greater proportion of the baseflow river community and decreased significantly under actual stormflow conditions (Chaudhary et al 2018), which is what we observed here in the simulated stormflow and baseflow microcosms.…”

“…Rhodocyclaceae in particular are common inhabitants of nutrient/substrate-rich environments such as wastewater and impacted urban streams (Chaudhary et al 2018). Comamonadaceae are also abundant in freshwater environments (Balmonte et al 2016;Shaw et al 2008) and have previously been found to dominate in Lake Michigan (Mueller-Spitz et al 2009), the freshwater source of the river we studied here.…”

“…Based our previous observations of tetracycline resistance genes and ammonia oxidation genes in metagenomic datasets from both the O'Brien WWTP effluent and NSC river water (Chaudhary et al 2018), we hypothesized that these functions could be affected by UV treatment. In addition, although the present 16S rRNA amplicon-based study focuses on microbial community composition rather than function, Phylogenetic Investigation of Fig.…”

“…For example, in a recent study of two WWTPs in Wisconsin, USA, we estimated that ~30 x 10 12 bacterial cells per day are released from each plant's effluent into Lake Michigan, despite removal of most bacterial biomass (Chu et al 2018;Petrovich et al 2018). Futhermore, the impact of effluent on receiving water bodies can be greater after rain events that increase discharge from WWTPs (Chaudhary et al 2018;Meziti et al 2016). Despite this, the primary method for assessing WWTP discharge water quality continues to rely on measuring fecal indicator bacteria (FIB) and largely ignores other microorganisms, genes, and many chemical contaminants (United States Environmental Protection Agency 2018).…”