Spatio-temporal variations in the physiological profiles of streambed bacterial communities: implication of wastewater treatment plant effluents

Abstract

The e uents of wastewater treatment plants (WWTPs) represent a complex mixture of nutrients and toxic substances, thus, the potential exists for the e uents to signi cantly impact the biochemical characteristics and bacterial communities of the receiving water. We examined spatial and seasonal patterns, and the impact of e uents on microbial biomass, bacterial community structure, and metabolic diversity on a fourth-order stream. We took triplicate sediment samples at ve different locations along a 5,000m transect over three sampling periods. We quanti ed bacterial community structure as communitylevel physiological pro les and biomass with phospholipid phosphate analysis. Our ndings highlight the worrisome impacts of e uents on microbial biomass and bacterial metabolic diversity on the receiving water. Microbial biomass was signi cantly higher at the WWTP outfall compared to upstream and downstream sites and correlated positively with sediment physicochemical parameters. Furthermore, our data revealed signi cant spatial differences in bacterial community structure in the context of WWTP impact. High nutrient availability (lower carbon/nitrogen ratios) at the outfall increased site-speci c bacterial metabolic diversity in winter but decreased the same in fall. Seasonal changes in the sedimentary microbial biomass and bacterial carbon substrate utilization were evident regardless of the spatial variations or impacts of the wastewater e uents. Communities in fall showed more versatile substrate utilization patterns than the winter communities. These results suggest that WWTP e uents signi cantly increased microbial biomass and highlight its mixed effects on bacterial community structure and metabolic diversity. Also, our data underscore a close association between sedimentary physicochemical parameters and the associated microbial functional activities.

Lotic Ecosystem Sediment Microbial Communities’ Resilience to the Impact of Wastewater Effluents in a Polluted European Hotspot—Mureș Basin (Transylvania, Romania)

“…Moreover, they show the impact of WWTP effluent on downstream microbial communities, which have shifted from the microbial structure found in the upstream sites to the microbial structure of the WWTP effluent. This result was expected, as other studies have also found WWTP effluent to have an impact on downstream microbial communities [93,136,139,169,171]. However, unlike our study, these studies only looked immediately downstream of the WWTP and not at the whole river.…”

“…Several studies have shown that this impact results in a reduction in the alpha diversity in sites immediately downstream of WWTPs [129,137], while others have shown a change in the balance between autotrophic and heterotrophic bacteria [166]. Other studies detect no change in alpha diversity before and after the WWTP [167][168][169]. The apparent lack of impact on alpha diversity might be explained by the fact that, while micropollutants can negatively affect the abundance of certain taxa, nutrients can favor the growth of others [166].…”