Untangling microbiota diversity and assembly patterns in the world's longest underground culvert water diversion canal.

The long-distance underground box culvert water transport system (LUBWT) is a crucial link between the source of drinking water and the consumers. It must ensure the stability of water quality during transportation. However, uncontrollable microbial growth can develop in the water delivery system during the long delivery process, posing a risk to health and safety. Therefore, we applied 16 s and 18 s gene sequence analysis in order to study microbial communities in box culvert waters sampled in 2021, as well as a molecular ecological network-based approach to decipher microbial interactions and stability. Our findings revealed that, in contrast to natural freshwater ecosystems, micro-eukaryotes in LUBWT have complex interactions such as predation, parasitism, and symbiosis due to their semi-enclosed box culvert environment. Total nitrogen may be the primary factor affecting bacterial community interactions in addition to temperature. Moreover, employing stability indicators such as robustness and vulnerability, we also found that microbial stability varied significantly from season to season, with summer having the higher stability of microbial communities. Not only that but also the stability of the micronuclei also varied greatly during water transport, which might also be related to the complex interactions among the micro-eukaryotes. To summarize, our study reveals the microbial interactions and stability in LUBWT, providing essential ecological knowledge to ensure the safety of LUBWT's water quality.