Increased anthropogenic activities destabilized bacterial co-occurrence
networks in a subtropical river
Abstract
Previous studies suggested that in an ecological co-occurrence network
with a large proportion of strongly positive correlations, the network
members may respond synchronously to environmental changes (e.g
synchronously become extinct), resulting in instability of network.
Anthropogenic activities have strong influences on the microbial
community composition and diversity in river ecosystems, but how their
influences on the stability of microbial co-occurrence networks remain
unclear. In this study, we used nutrient concentrations (nitrogen and
phosphorus) as an indicator for anthropogenic actives, 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 proportion and correlations
coefficients of positive correlations for bacterial co-occurrence
networks strongly and positively correlated with the nutrient
concentrations, indicating increased anthropogenic activities
destabilized the networks in midstream and downstream areas. To further
explore the mechanisms, we found that the changes of network stability
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 a
largely and strongly positive module in the midstream and downstream
networks, therefore destabilized the networks. Based on network
perspective, our results provide new insight in the mechanisms of
anthropogenic activities alter riverine microbial communities.