混合营养方式是原生生物一种很普遍的营养策略，近年来随着越来越多的原生生物被发现为混养方式，且在许多海区混养原生生物的多样性和生物量都非常高，暗示着它们在海洋生态系统的营养盐和有机物循环中起着重要的作用。然而，目前为止对于混养原生生物的基础生物学和生态学研究还非常缺乏，特别是对于富营养的河口生态系统，这大大限制了对该类群生物在海洋生态系统中作用的理解和认识。本课题旨在以珠江口为研究生境，研究河口生态系统中混养原生生物的组成和分布情况以及影响这些特征的环境因素，并通过实验生态学手段，在实验室和野外条件下，着重研究光照和营养盐对混养原生生物生长和摄食的影响，从而为深入理解海洋微食物网的动态变化以及混养原生生物的作用提供基础数据，为改进和完善海洋食物网模型提供重要的理论依据。

Mixotrophy is a common nutritional strategy in marine protists. Recently, more and more marine protists were found to be mixotrophic. The incredible diversity of mixotrophic protists, as well as their high biomass in many marine regions, suggests that they may play an important role in the cycling of nutrients and organic matter in the marine ecosystems. However, researches concerning the biology and ecology of mixotrophic protists，especially in eutrophic estuarine ecosystems are still scarce so far, which limits our understanding on their roles in the marine ecosystems. This proposal aims to take the Pearl River Estuary as studing habitat and investigate the composition and distribution pattern of mixotrophic protists as well as influencing factors in estuarine ecosystem. By conducting experiments in the laboratory and field, we aim to investigate the effects of light and nutrients on the growth and feeding of mixotrophic protists. This research can provide basic data for better understanding the roles of mixotrophic protists in the dynamics of marine microbial food webs. It also can provide an important theoretical basis for the improvement of marine food web models.