Base on cluster analysis and calculating indicator value have provided basic information about seasonal change of phytoplankton in the south-east of Vietnam seawater. There are some species present all year round with high density such as: Coscinodiscus radiatus, Odontella. regia, whereas some species only grow at a few month in the year, such as: Climacodium biconcavum is species of tropical pelagic zone in dry season (March)
or Pseudosolenia calcar-avis, Odontella (Biddulphia) regia is species group of eurythermes and euryhalines in May
in west season (August and November) are the group of low salinity species and brackish species such as: Chaetoceros cun'isetus. Hemiaulus sinensis, Chaetoceros diversus and so on.