I. Introduction
Phytoplankton is the most primary producer in the marine ecosystem and plays an important role in ecological balance, material circulation and energy flow [1]. It is rich in protein, unsaturated fatty acids, carotenoids, polysaccharides and other bioactive substances. It has a broad prospect for application in medicine, cosmetics, feed, health food, bio fertilizer and other industries [2]. Meanwhile, phytoplankton is also a main reason for red tide [3]. It is well known that the red tide decreases the dissolved oxygen in seawater and blocks sunlight for undersea photosynthesis. As a result, the ecological disaster is frequently occurred to cause mass death of sea creatures, and even it may lead to toxic effect on the food chain to threaten human life. In this cycle, microalgae are the main source of phytoplankton, and it is vital to recognize the microalgae in single-cell level as the foundation in disaster warning or industrial utilization.