印度洋海域大气气溶胶和海洋微表层中细菌的特征及其冰核活性

Marine aerosols have been shown to act as condensation and ice nuclei in cloud formation process and are consequently hypothesized to have significantly direct and indirect effects on the global climate. The sea surface microlayer (SML), i.e., the boundary layer interface between the atmosphere and the ocean, is critical to a diverse range of Earth system processes including the ocean–atmosphere exchange of aerosols. Bacteria and other microorganisms are enriched in the SML and ejected into the atmosphere, and they constitute a major fraction of marine aerosols. However, there has been a large lack of the knowledge regarding the role of bacteria playing in the ocean-aerosol-cloud-climate links. In this study, we will simultaneously collect marine aerosol and the SML water samples in the Indian Ocean, and analyze the characteristics of bacteria in both media, including the abundance, viability, and community structure. The exchange of bacteria between the ocean and the atmosphere and the relative contributions of marine and terrestrial sources to airborne bacteria in marine air will be estimated. The factors influencing the existence of bacteria in the marine atmosphere will be explored. In addition, the ice nucleation properties of particles and bacteria in both media will be measured to assess the effect of bacteria in the marine ecosystem on the formation of ice nuclei in clouds. These results will be critical to improve our understanding of the development and evolution of bacteria in the marine ecosystem, and provide fundamental information on the role of microbiological/bacterial activities in regulating the marine ecosystem and the global climate.

海洋气溶胶能在云形成过程中充当云凝结核和冰核，直接和间接影响全球气候。作为大气和海洋的交界面，海洋微表层对气溶胶的海-气交换等重要地球系统过程十分关键。细菌等微生物在海洋微表层富集并释放到大气中，成为海洋气溶胶的重要组成。然而，我们对细菌在海洋-气溶胶-云-气候系统耦合中的作用的认识仍在很大程度上存在不足。本项目拟在印度洋海域同时采集大气气溶胶和海洋微表层样品，测量两种介质中细菌的浓度及活性、存在状态与群落结构等特性，估算细菌的海-气通量及海洋源和陆地源对海洋大气细菌的贡献，确定影响海洋大气中细菌存在的主要因素。同时，测量两种介质中颗粒物及细菌的冰核活性，评估海洋生态系统中细菌对云中冰核形成的贡献。本项目研究结果将有助于理解海洋生态环境中细菌的发展和演化规律，阐明海洋生态系统中细菌等微生物活动与气候变化之间的联系。

海洋气溶胶能在云形成过程中充当云凝结核和冰核，直接和间接影响全球气候。目前对细菌等生物气溶胶在海洋-气溶胶-云-气候系统耦合中的作用的认识仍在很大程度上存在不足。项目执行期间，我们综述了海洋大气生物气溶胶对云形成和全球气候影响的最新研究进展；采集了印度洋海域海洋气溶胶和海水等介质样品，并进行实验室分析其理化特性；搭建了一套可用于研究浸润冻结模式下非均质冰核的可靠装置（TJU-INA），性能优良，应用于研究印度洋海洋气溶胶和海水冰核活性测试。观测发现，南海至印度洋开放海域荧光气溶胶颗粒物（FAPs）浓度比近海海域低1-2个数量级（约10-10^2 L-1），占总颗粒物比例小于20%，主要由海洋排放的细菌和真菌等生物气溶胶贡献；南海近海海域和科伦坡港口等地FAPs浓度比例可达40-80%，可能同时受到陆地源生物气溶胶和其他干扰物的影响。利用激发-发射矩阵（EEM）荧光光谱技术结合平行因子分析（PARAFAC）方法研究得出，溶解性有机质（DOM）的荧光组分以酪氨酸、色氨酸等类蛋白类组分为主，表明表层海水中微生物源对DOM的贡献较大，可能对海洋大气生物气溶胶具有重要贡献。项目研究结果有助于理解海洋大气生态环境中微生物的发展和演化规律，阐明海洋生态系统中微生物活动与气候变化之间的联系。