Spatiotemporal dynamics of ammonium monooxygenase (amoA) genes in sediments of the aquaculture area in the Yellow Sea Cold Water Mass

Ammonia oxidation is a fundamental process in the marine nitrogen cycle, driving the transformation of ammonia into nitrate and playing a crucial role in maintaining nitrogen balance in deep-sea ecosystems. Ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) are kay contributors to this process; however, their dynamics in deep-sea aquaculture environments remain poorly understood. This study investigated the spatiotemporal variations in the diversity, community composition, and abundance of archaeal and bacterial amoA genes in sediments from Yellow Sea Cold Water Mass aquaculture area. Results revealed that AOB exhibited more OTUs as well as higher diversity and richness than AOA. Most AOA and AOB were classified into the genera Nitrosopumilus and Nitrosomonas, respectively. The highest abundance of amoA gene copies was observed in December. Although bioindicators for both AOA and AOB communities were detected across all sampling sites and times, none of them could be identified as aquaculture-derived indicators. Neutral community model indicated that AOB community assembly was primarily shaped by stochastic processes (R² = 88.6 %), whereas the AOA community was more influenced by environmental factors (R² = 61.3 %). Key environmental drivers, including bottom water temperature and sediment carbon content, significantly affected archaeal amoA gene abundance and AOA indicator abundance. These findings provide new insights into the distinct ecological roles and assembly mechanisms of AOA and AOB communities in the YSCWM. Understanding these microbial dynamics is essential for evaluating nitrogen cycling stability in deep-sea aquaculture environments and developing sustainable management strategies for marine aquaculture in the YSCWM.