南海混合营养真核藻类的物种鉴定和细菌摄食压力估算

小型真核藻类是开阔大洋光合生物的主要类群，是初级生产力的重要贡献者。许多这些含有叶绿体的鞭毛藻类能够通过摄食细菌获取额外的营养物质和能量，因此称之为混合营养藻类。它们的存在能够增加初级生产力和能量向上传输的效率，显著提升生态系统的颗粒碳输出。我国南海存在大量物种丰富的小型真核藻类，但对它们的混合营养模式研究尚显不足。该课题旨在从定性和定量两个方面调查南海典型海区的混养藻类，通过大规模的现场分离获取该海区的代表性混养藻株，经物种鉴定之后用于摄食实验测定对细菌蓝细菌的摄食速率，最终结合它们的现场丰度估算其对细菌群落的摄食压力。不同于海洋届普遍采用的荧光标定灭活细菌FLB的方法，该项目通过喂食模式藻株未经处理的天然细菌，能够测得更加准确真实的摄食速率。揭示的混养藻类物种和丰度信息能够帮助评估它们在南海生态系统中的作用，估算的摄食压力能够帮助填补生态模型中细菌－藻类的物能流数值。

Small eukaryotes are an important component of autotrophic community and a major contributor of primary production in open ocean. Many of these chloroplasts-containing eukaryotic flagellates can obtain extra nutrients and energy through grazing on bacteria, and are thus mixotrophic. Mixotrophs in an ecosystem can significantly increase particulate carbon export through enhanced primary production and energy transport efficiency to higher trophic levels. South China Sea harbors a large amount of small eukaryotes which are high in abundance and diversity, though studies on their mixotrophic lifestyle remain surprisingly little. This project aim to investigate these mixotrophs both qualitatively and quantitatively in typical environments of South China Sea. A combined methodology will be applied in this project, including broad isolation and identification of model mixotrophic strains through in situ bacterial prey enrichment, measurements of bacterial and cyanobacterial grazing rates via laboratory grazing experiments and ultimately, their grazing impact on bacterial community based on abundance results from the field will be calculated. The application of feeding model strains live, unprocessed natural bacterial culture is fundamentally different from the Fluorescently Labeled Bacteria method and can provide more accurate and reliable grazing rate estimations. Mixotrophic taxonomy and abundance results revealed from this work can ultimately shed light on the functional role of mixotrophic eukaryotes in South China Sea and provide numbers of nutrients and energy flow between bacteria and eukaryotes for ecological models.