Introduction

Approximately, there are 330 aquatic organisms known to cause red tide in the world in which 73 species had been recorded to cause red tide in Hong Kong.

Diatoms and dinoflagellates are two common groups making up the phytoplankton community in Hong Kong and many of the red tide causative species belong to these 2 groups. There are however other groups of phytoplankton species also recorded to cause red tide in Hong Kong. They are collectively placed in the category "Others".