Table_1_Characteristics and particularities of bacterial community variation in the offshore shellfish farming waters of the North Yellow Sea.docx

Bacteria in coastal waters drive global biogeochemical cycling and are strongly related to coastal environmental safety. The bacterial community in offshore shellfish farming waters of North China has its own characteristics and particularities, while the knowledge is limited. In this study, the bacterial community characteristics, the particularities of bacterial community in the waters with surface cold patches (SCPs) and the variation of pathogenic bacteria were investigated in the offshore shellfish farming waters in the North Yellow Sea (NYS) from 2017 to 2019. For all studied samples, Desulfobacterales acted as the keystone species taxon in microbial co-occurrence networks, and the proportional abundance of Actinobacteriota was found to be as low as 1.3%. The abundance of Marinobacter and Synechococcus was remarkably prominent in 13 genera with nitrogen-transforming function. The top two different bacterial functions in the spatial analysis (between the waters with SCPs and the ambient waters) were xenobiotics biodegradation and metabolism and metabolism of cofactors and vitamins, which were same with that in the seasonal analysis (between spring and summer). The abundance differences of most pathogenic bacteria analyzed in this study (11 out of 12 genera) also had the same variation dynamics between the spatial analysis and the seasonal analysis. An ANN predictive model for Vibrio abundance was constructed for Vibrio forecasting, with acceptable predictive accuracy. According to the above results, the bacterial community in the shellfish aquaculture waters in this study was characterized by the enhancing ability of nitrogen removal. Temperature was concluded as the predominant environmental factor to drive the variation of bacterial community function and pathogenic bacteria patterns in the offshore shellfish farming waters with SCPs. The results of this study will further our understanding of the bacterial community characteristics in offshore shellfish farming waters, and help for Vibrio forecasting and coastal environmental safety in aquaculture seawater.

近岸海域的细菌驱动着全球生物地球化学循环，且与近岸环境安全密切相关。中国北方近海贝类养殖水域的细菌群落具有其独特特征与特殊性，但目前相关认知仍较为有限。本研究于2017-2019年期间，针对北黄海（North Yellow Sea, NYS）近海贝类养殖水域展开调研，解析了该水域的细菌群落特征、表层冷斑（surface cold patches, SCPs）水域的细菌群落特殊性，以及致病菌的变化规律。所有供试样品中，脱硫杆菌目（Desulfobacterales）均为微生物共现网络（microbial co-occurrence networks）中的关键类群，而放线菌门（Actinobacteriota）的相对丰度仅为1.3%。在13个具有氮转化功能的菌属中，海杆菌属（Marinobacter）与聚球藻属（Synechococcus）的丰度最为显著。在空间分析（表层冷斑水域与周边水域的对比）中，差异最显著的两项细菌功能分别为外源生物降解与代谢、辅因子与维生素代谢；该结果与季节分析（春季与夏季的对比）所得结果一致。本研究分析的多数致病菌（12个菌属中的11个），其丰度差异在空间分析与季节分析中也呈现出一致的变化动态。本研究构建了用于预测弧菌（Vibrio）丰度的人工神经网络（Artificial Neural Network, ANN）预测模型，该模型具有可接受的预测精度。基于上述结果，本研究中的贝类养殖水域细菌群落以增强的脱氮能力为典型特征。温度被确定为驱动表层冷斑近海贝类养殖水域细菌群落功能与致病菌分布模式变化的主要环境因子。本研究结果将加深我们对近海贝类养殖水域细菌群落特征的认知，并可为养殖海水的弧菌预测与近岸环境安全保障提供理论支撑。