Marine aquaculture wastewater is one of the major sources of nitrogen pollution in coastal areas, and excessive discharge poses a threat to human health and the marine ecosystem. In order to investigate the nitrogen metabolism potential of microorganisms in marine aquaculture water, metagenomic sequencing was conducted, and microbial communities involved in nitrogen metabolism on composite filler biofilms and their contributions to nitrogen metabolism functions were analyzed based on KEGG annotation. Metagenomic analysis revealed that nitrogen metabolism microorganisms were primarily composed of Proteobacteria, Planctomycetota, Bacteroidota, and Firmicutes. KEGG results indicated the presence of complete nitrogen metabolism pathways within the biofilm. Analysis of nitrogen metabolism modules and relative enzyme abundance showed that the nitrification module was much less abundant compared to denitrification. Denitrification, dissimilatory nitrate reduction, and ammonia conversion to amino acids were the major modules of nitrogen metabolism in the biofilm, reflecting the main nitrogen transformation pathways. The study systematically revealed key driving taxa in the nitrogen cycle within the biofilm. Proteobacteria, Planctomycetota, Bacteroidota, and Verrucomicrobia were identified as the major executors of nitrogen metabolism pathway modules and enzyme functions in the biofilm. This research underscores the diverse microbial communities cooperate to maintain the potential nitrogen removal capacity of the biofilm. This study provide new insights into the critical driving factors of nitrogen cycling in marine aquaculture wastewater, which can serve as a scientific basis for the efficient purification of aquaculture wastewater.

海水养殖废水是沿海地区氮污染的主要来源之一，超标排放对人类健康和海洋生态系统构成威胁。为了探究海水养殖水体中微生物的氮代谢潜力，进行了宏基因组测序，并基于KEGG注释分析了复合填料生物膜上参与氮代谢的微生物群落及其对氮代谢功能的贡献。宏基因组分析表明，氮代谢微生物主要由变形菌门、浮霉菌门、拟杆菌门和厚壁菌门组成。 KEGG 结果表明生物膜内存在完整的氮代谢途径。对氮代谢模块和相对酶丰度的分析表明，与反硝化模块相比，硝化模块的丰度要低得多。反硝化、异化硝酸盐还原和氨转化为氨基酸是生物膜氮代谢的主要模块，反映了主要的氮转化途径。该研究系统地揭示了生物膜内氮循环的关键驱动类群。变形菌门、浮霉菌门、拟杆菌门和疣微菌门被确定为生物膜中氮代谢途径模块和酶功能的主要执行者。这项研究强调了不同的微生物群落合作维持生物膜潜在的脱氮能力。该研究为海水养殖废水氮循环的关键驱动因素提供了新的见解，可为水产养殖废水的高效净化提供科学依据。