Watershed Urbanization Linked to Differences in Stream Bacterial Community Composition

Abstract

Urbanization strongly influences headwater stream chemistry and hydrology, but little is known about how these conditions impact bacterial community composition. We predicted that urbanization would impact bacterial community composition, but that stream water column bacterial communities would be most strongly linked to urbanization at a watershed-scale, as measured by impervious cover, while sediment bacterial communities would correlate with environmental conditions at the scale of stream reaches. To test this hypothesis, we determined bacterial community composition in the water column and sediment of headwater streams located across a gradient of watershed impervious cover using high-throughput 16S rRNA gene amplicon sequencing. Alpha diversity metrics did not show a strong response to catchment urbanization, but beta diversity was significantly related to watershed impervious cover with significant differences also found between water column and sediment samples. Samples grouped primarily according to habitat—water column vs. sediment—with a significant response to watershed impervious cover nested within each habitat type. Compositional shifts for communities in urbanized streams indicated an increase in taxa associated with human activity including bacteria from the genus Polynucleobacter, which is widespread, but has been associated with eutrophic conditions in larger water bodies. Another indicator of communities in urbanized streams was an OTU from the genus Gallionella, which is linked to corrosion of water distribution systems. To identify changes in bacterial community interactions, bacterial co-occurrence networks were generated from urban and forested samples. The urbanized co-occurrence network was much smaller and had fewer co-occurrence events per taxon than forested equivalents, indicating a loss of keystone taxa with urbanization. Our results suggest that urbanization has significant impacts on the community composition of headwater streams, and suggest that processes driving these changes in urbanized water column vs. sediment environments are distinct.

In search of microbial indicator taxa: shifts in stream bacterial communities along an urbanization gradient

“…These results are in contrast with widely reported decreases in the diversity of ciliate, macroinvertebrate and fish communities in urban streams (Helms et al, 2005;Moore and Palmer, 2005;Lear et al, 2011). This finding is consistent with the hypothesis recently put forward by Hosen et al, (2017), who suggested that similar levels of bacterial diversity are maintained across the urbanization gradient because the introduction of novel bacterial taxa from sewage, water distribution or septic systems, and stormwater may compensate for the loss of taxa sensitive to urban conditions.…”

Pulling apart the urbanization axis: patterns of physiochemical degradation and biological response across stream ecosystems

“…Contrary to our expectations (Perryman et al 2008, Wang et al 2011, Hosen et al 2017, microbial communities, as measured by OTU richness and community composition, did not shift perceptibly along the development gradient. The 2 denitrifier functional genes we measured with T-RFLP indicated that some community members responded to temperature (nirK) or to substrate supply and contamination (nosZ) because these variables were correlated with the major axes of variation in composition.…”

“…* 5 p < 0.05, ** 5 p < 0.01, *** p < 0.001, NS 5 not significant. fects of urban hydrology and water quality on microbial community composition still are not well understood (Hosen et al 2017). In a synthesis of lotic microbial diversity studies, Zeglin (2015) found that microbial diversity was negatively affected by metals, temperature, substrate type, or hydrology more commonly than by more general effects of land use or nutrient concentrations.…”

Aquatic Bacterial Communities Associated With Land Use and Environmental Factors in Agricultural Landscapes Using a Metabarcoding Approach

“…Localized sorting of aquatic bacterial communities in response to changes in water physiochemical properties has been previously reported (Moss, 2008 ; Hu et al, 2014 ; Sangchan et al, 2014 ; Staley et al, 2015 ; Van Rossum et al, 2015 ; Borges et al, 2017 ; Hosen et al, 2017 ). Jurelevicius et al ( 2013 ) demonstrated that different Proteobacteria (e.g., Achromobacter spp.)…”