摘要： 为探究不同封闭式养殖模式下吉富罗非鱼(Oreochromis niloticus)越冬期间的微生物群落变化，本研究采用高通量测序技术，比较分析了循环水养殖系统（RAS）与生物絮团系统（BFT）中鱼体肠道及水体的微生物群落结构。结果表明，养殖过程中RAS组水体、RAS组生物滤池滤料及BFT组水体的Chao1指数均呈上升趋势，RAS组水体和生物滤池滤料的多样性在末期下降，BFT组水体微生物多样性上升；养殖末期RAS组鱼体肠道与鳃的物种丰富度和多样性均高于BFT组。养殖初期RAS组水体优势菌为变形菌门(Proteobacteria, 75%)和副球菌属(Paracoccus, 34%)，BFT组水体的为厚壁菌门(Firmicutes, 86%)和芽孢杆菌属(Bacillus, 85%)；养殖末期BFT组水体优势菌门转变为绿弯菌门(Chloroflexi, 43%)。养殖初期鱼体肠道以梭杆菌门(Fusobacteria, 62%)和鲸杆菌属(Cetobacterium, 61%)为主，养殖末期RAS组以变形菌门(35%)和绿弯菌门(31%)为优势菌门，优势菌属为norank_o__JG30-KF-CM45(25%)和包西氏菌属(Bosea, 12%)；BFT组优势菌门为变形菌门、放线菌门(Actinobacteria)和厚壁菌门，优势属包括芽孢杆菌(16%)、鲸杆菌(13%)和norank_f__Caldilineaceae(13%)。养殖末期BFT组水体与鱼体肠道的微生物群落表现出较强一致性，共同优势菌门包括梭杆菌门、变形菌门、绿弯菌门及拟杆菌门(Bacteroidota)；RAS组水体与鱼体肠道间微生物相关性较弱。综上所述，不同养殖模式显著改变了养殖水体和吉富罗非鱼肠道微生物群落结构，利于罗非鱼的健康。与RAS相比，BFT系统更能增加罗非鱼肠道的微生物群落多样性。因此，在越冬养殖过程中，建议将BFT系统作为吉富罗非鱼的优选养殖模式。

关键词: 吉富罗非鱼, 循环水养殖系统, 生物絮团技术, 微生物群落

Abstract:  Genetically Improved Farmed Tilapia (GIFT tilapia, Oreochromis niloticus), a selectively bred strain of Oreochromis niloticus is a globally important aquaculture species known for its rapid growth and stress resistance. As a tropical fish species, GIFT tilapia is extremely sensitive to low temperatures. The overwintering period has become a major challenge for its aquaculture in most regions of China. To improve overwintering survival rates and ensure sustainable aquaculture, closed aquaculture systems have gained increasing attention. Closed aquaculture systems mainly include recirculating aquaculture systems (RAS) and biofloc technology (BFT). They offer significant advantages in water conservation, temperature control, and environmental sustainability. However, the microbial community dynamics and ecological interactions in RAS and BFT systems under overwintering conditions remain unclear. This study investigated the structural evolution of microbial communities in water and fish tissues under RAS and BFT systems during overwintering. High-throughput 16S rDNA sequencing was employed to characterize these communities. In this study, two treatment groups were established: RAS groups and BFT groups. Each group included three replicates. Both groups were stocked with juvenile GIFT tilapia. They were maintained under identical stocking densities and environmental management. At the beginning and end of the culture period, samples were collected from the water, biofilter media (RAS groups), biofloc particles (BFT groups), as well as from the intestinal and gill tissues of the fish. These samples were used for microbial DNA extraction and subsequent diversity analysis. In addition, key water quality parameters, including ammonia nitrogen, nitrite, and nitrate were monitored to evaluate environmental changes during the culture process. Alpha diversity analysis revealed that the Chao1 and Simpson indices of RAS water, biofilter media, and BFT water samples increased during the overwintering period. In contrast, the microbial diversity in the intestinal and gill tissues of the fish showed a decreasing trend. At the early stage of culture, Proteobacteria (75%) dominated the microbial community in the RAS groups, with Paracoccus (34%) being the predominant genus. Meanwhile, the BFT groups was mainly composed of Firmicutes (86%) and Bacillus (85%). By the end of the culture period, the proportion of Proteobacteria in the RAS system had decreased to 26%. Chloroflexi (43%) became dominant in the BFT groups, and the relative abundance of Bacillus dropped to 3%. The dominant phyla in the biofilter shifted from Proteobacteria in the early stage to Chloroflexi and Actinobacteria later on. Notably, at the end of the culture period, the microbial composition of the water and GIFT tilapia intestines in the BFT groups showed strong consistency. They shared dominant phyla including Fusobacteria, Proteobacteria, Chloroflexi, and Bacteroidota. In contrast, the microbial correlation between the water and fish intestines in the RAS groups was relatively weak. In summary, different overwintering aquaculture models significantly altered the microbial communities in the rearing water and the intestinal tract of GIFT tilapia. This study provides some theoretical foundation for the development of low-temperature overwintering strategies for GIFT tilapia, and offers practical guidance for the optimization and application of RAS and BFT systems. For overwintering aquaculture, it is recommended to choose the BFT systems as the preferred model for GIFT tilapia.

Key words: Genetically Improved Farmed Tilapia (GIFT tilapia), recirculating aquaculture systems, biofloc technology, microbial community