Microbial community shifts in streams receiving treated wastewater effluent
Cresten Mansfeldt1, Kristy Deiner2, Elvira Mächler3
1Eawag: Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland.
The Science of the Total Environment
|December 31, 2019
Summary
Wastewater treatment plant (WWTP) effluent significantly alters stream microbial communities, introducing human-gut bacteria and decreasing beneficial microbes. These changes indicate potential shifts in stream ecosystem function.
Area of Science:
- Environmental microbiology
- Ecotoxicology
- Stream ecology
Background:
- Wastewater treatment plant (WWTP) effluents release microorganisms into watersheds.
- Understanding microbial community shifts in streams receiving WWTP effluent is crucial for assessing ecological impact.
Purpose of the Study:
- To characterize bacterial community shifts in headwater streams affected by WWTP effluent.
- To determine the extent to which downstream microbial communities are a mixture of upstream and effluent sources.
Main Methods:
- Sampling of water-column microorganisms from upstream, downstream, and WWTP effluent sites.
- Bacterial community characterization using 16S rRNA gene V3-V4 region sequencing.
- Ordination analyses to assess community profile mixing.
Main Results:
- Downstream bacterial communities showed a mixture of upstream and effluent profiles.
- WWTP effluent contributed >50% to the downstream community in 14 out of 23 sites.
- A human-gut bacterium, Ruminococcus, showed a 30-fold increase downstream, serving as a potential bioindicator. Cyanobacteria/Chloroplast abundance decreased, not explained by hydraulic mixing alone.
Conclusions:
- WWTP effluent significantly alters stream microbial composition, introducing human-gut bacteria and reducing autotrophic groups.
- These shifts can lead to broader changes in stream ecosystem function.
- Specific microbial sequence variants, like Ruminococcus, can serve as bioindicators of wastewater influence.
