Abstract

Water column mixing homogenizes thermal and chemical gradients which are known to define distribution of microbial communities and influence the prevailing biogeochemical processes. Little is however known about the effects of rapid water column mixing on the vertical distribution of microbial communities in stratified reser-voirs. To address this knowledge gap, physicochemical properties and microbial community composition from 16 S rRNA amplicon sequencing were analyzed before and after mixing of vertically stratified water-column bioreactors. Our results showed that alpha-diversity of bacterial communities decreased from bottom to surface during periods of thermal stratification. After an experimental mixing event, bacterial community diversity experienced a significant decrease throughout the water column and network connectivity was disrupted, fol-lowed by slow recovery. Significant differences in composition were seen for both total (DNA) and active (RNA) bacterial communities when comparing surface and bottom layer during periods of stratification, and when comparing samples collected before mixing and after re-stratification. The dominant predicted community as-sembly processes for stratified conditions were deterministic while such processes were less important during recovery from episodic mixing. Water quality characteristics of stratified water were significantly correlated with bacterial community diversity and structure. Furthermore, structural equation modeling analyses showed that changes in sulfur may have the greatest direct effect on bacterial community composition. Our results imply that rapid vertical mixing caused by episodic weather extremes and hydrological operations may have a long-term effect on microbial communities and biogeochemical processes.

Keywords

Water stratification; Rapid mixing event; Bacterial communities; Community assembly; Vertical water

Published in

Environmental Research
2024, Volume: 243, article number: 117886
Publisher: ACADEMIC PRESS INC ELSEVIER SCIENCE

SLU Authors

• Bertilsson, Stefan

  • Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Microbiology
Environmental Sciences
Oceanography, Hydrology, Water Resources


Publication identifier

DOI: https://doi.org/10.1016/j.envres.2023.117886

Permanent link to this page (URI)

https://res.slu.se/id/publ/128014