Microbial community structure and congruence responses to multiple environmental stressors: insights from a mesocosm experiment

Multiple stressors present a significant challenge to global freshwater ecosystems, particularly affecting microbial dynamics. The response of microbial communities at the water and sediment interface varies depending on the specific stressors and habitat conditions. Previous studies have shown that biodiversity and community structure change predictably along single stress gradients. However, the interactions among multiple stressors and their combined effects on microbial communities, especially in water and sediment remain poorly understood. To investigate these interactions, 48 mesocosms were constructed to simulate shallow freshwater lake ecosystems, exposing them to the individual or combined effects of temperature (continuous warming (W), multiple heatwaves (H)), glyphosate herbicide (G), and eutrophication (E) induced by nitrogen and phosphorus addition. Results indicated that eutrophication significantly enhanced the congruence of microbial species richness at the water and sediment interface, and functional richness ( p ​< ​0.05). Changes in beta-diversity in both water and sediment were primarily driven by temperature and eutrophication, with effects varying according to microbial habitat. The combined effects of temperature and eutrophication on beta-diversity were either antagonistic interactions (less than) or additive interactions (approximating the cumulative impact of each factor individually). Glyphosate herbicide had no significant influence on microbial congruence or diversity at the water and sediment interface, nor did it interact with warming or eutrophication. This research provides insights into the changes and adaptations of freshwater ecosystems under multiple stressors from a microbial community perspective. These findings have important implications for developing cost-effective ecological monitoring strategies for freshwater systems. • Eutrophication drives microbial community congruence at the water-sediment interface. • Eutrophication affects sediment microbial beta diversity, while warming impacts communities in water. • The interactive effects of multiple stressors on microbial community diversity primarily manifest as antagonistic effects. • Both single and multiple stressors enhance species and functional turnover in microbial communities.