Abstract
Nitrite oxidation, a pivotal process in the nitrogen cycle driven by microorganisms, is primarily carried out by nitrite-oxidizing bacteria (NOB). While extensive studies on Nitrospira have been conducted in terrestrial habitats, knowledge of Nitrospira in marine sediments remains limited. Therefore, we employed high-throughput sequencing analysis to systematically explore the community structure, assembly processes and potential interactions of Nitrospira in the eastern China marginal seas. Our results exhibit pronounced spatial heterogeneity in Nitrospira communities across seas. Widespread distribution of Nitrospira taxa was observed, with Nitrospira lineage II emerging as the most important group in this study. Based on the neutral community model (NCM), normalized stochasticity ratio (NST) and beta nearest-taxon-index (βNTI) analysis, deterministic processes predominantly shaped the community assembly of Nitrospira. Complex interspecies interactions among Nitrospira were observed with molecular ecological network analysis, and the community in the East China Sea showed the highest complexity, while the community displayed the greatest stability in the South Yellow Sea. In addition, the Nitrospira communities were notably influenced by geographic distances and environmental factors, including salinity, temperature, dissolved oxygen concentration and dissolved inorganic nutrient concentration. These results may expand our understanding of Nitrospira in marine environments and enhance our insights into the marine nitrogen cycle.