Anthropogenic Activities Destabilized Bacterial Co-occurrence Networks in a Subtropical River

Abstract

Previous studies suggested that strong positive correlations between microbial taxa destabilized microbial co-occurrence network, because network members which had strong positive correlations with each other tended to decrease in abundance synchronously. Anthropogenic activities have strong influences on microbial community composition and diversity in riverine ecosystems, but how they influence the stability of microbial co-occurrence network remain unclear. In this study, we used nutrient concentrations (nitrogen and phosphorus) as an indicator for anthropogenic activities, and explored the effects of anthropogenic activities on the stability of bacterial co-occurrence networks in a subtropical river, Xiyuan River. The nutrient concentrations were higher in midstream and downstream areas than in upstream area of Xiyuan River. The average proportion and correlation coefficient of positive correlations were higher in midstream and downstream networks than in upstream networks, indicating frequent anthropogenic activities destabilized the bacterial co-occurrence networks. To further explore the mechanisms, we found that the changes of network stabilities were associated with the changes of bacterial functions. Anthropogenic activity tolerant bacteria (e.g. nutrient removal, aromatic degradation and pathogen bacteria) and their linked bacterial members formed the large and strong positive modules in the midstream and downstream networks, and thus destabilized the networks. Based on network perspective, our results provide a new insight in the mechanisms of how anthropogenic activities alter riverine microbial communities.