Spatio-temporal distribution of diatoms and dinoflagellates in the macrotidal Tanintharyi River estuary, Myanmar

Abstract

The spatio-temporal distribution of diatoms and dinoflagellates composition and abundance were analyzed to investigate their seasonal and neap–spring tidal dynamics in the tide-dominated tropical Tanintharyi River estuary (TRE), Myanmar in 2019. The salinity showed significant variations between seasons (F=32.86, P < 0.001) and the maximum salinity was found in the lower estuary. The turbidity was highest in the mid-upper estuary during spring tide in both seasons. Eighty-two species of microphytoplankton (Fifty-nine species of diatoms and twenty-three species of dinoflagellates) were observed and summarized as 15 groups based on their similarity in cell shapes and sizes. Diatoms were dominant over dinoflagellates in both seasons. The density of diatoms was maximum during the intermediate tide in both seasons. The density of dinoflagellates was maximum during the neap tide in the dry season while during the intermediate tide in the wet season. Spatially, abundances of both diatoms and dinoflagellates were maximum in the lower part of the estuary, which corresponds to high salinity. The abundance of diatoms was significantly different between seasons (F=4.14, P < 0.05). Further, chain-forming diatoms and surface extension dinoflagellates were the dominant groups throughout the estuary. The study indicates that the salinity, turbidity, and mixing driven by the seasons and the neap–spring tidal cycle can influence the distribution and abundance of diatoms and dinoflagellates in the TRE. The cell shape and size promote most aspects of their survival strategy.