Abstract

• Phytoplankton samples were collected from ten designated sampling stations from Kywe Ku bridge (Lat. 12º 31´ N and Long. 98º 47´ E) to Done Pale Aw (Lat. 12º 21´ N and Long. 98º 02´ E) covering inshore, nearshore and offshore, Myeik coastal waters from June 2011 to February 2013. A total of 135 phytoplankton species were identified. In the inshore water (Station 1 and Station 2), the species succession was evident by 8 species of diatoms. In the nearshore water (Station 3, Station 4, Station 5, Station 6 and Station 7), fifteen species of diatoms and one species of dinoflagellate were recorded as species succession. In the offshore water (Station 8, Station 9 and Station 10), there were twenty species of diatoms in the species succession. The quantity of physico-chemical parameters were: water temperature 25-30ºC, salinity 4-34‰, pH 7.1-8.2, phosphate 0.01-1.33 mg/l, nitrate 0.01-0.99 mg/l and transparency 0.51-9.0 m in the Myeik coastal waters. The diatoms were more dominant than the dinoflagellate in any season and their densities were always near 90%. The composition of dominant diatoms showed the different situations from the inshore, nearshore to offshore coastal waters. The succession of phytoplankton was positively correlated with some environmental factors such as transparency and temperature, however, the negative correlation was found with nitrate, phosphate, salinity, pH and rainfall in Myeik Archipelago.