Author(s): Lett Wai New; Gubash Azhikodan; Katsuhide Yokoyama; Masashi Kodama; Nay Oo Hlang; Nyo Nyo Tun
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Keywords: Diatoms; Dinoflagellates; Phytoplankton distribution; Neap-spring tidal cycle
Abstract: The present study was conducted to analyze the spatio-temporal distribution of diatoms and dinoflagellates in the macrotidal Tanintharyi River estuary during dry season. Water samples were collected by plankton net from surface water during the neap-spring tidal cycle from 28 February to 7 March 2019 from the downstream to the upstream through the estuary. Further, the environmental parameters were measured using CTD probe. The distribution and abundance of species was analyzed using compound microscope. The salinity was increased from neap to spring tide and it varied spatially from the downstream (26-30.7) to the upstream (2-7.3). Turbidity was increased from neap tide and reached highest value in spring tide at mid upper estuary. A total of 82 phytoplankton species consist ing of 59 diatoms and 23 dinoflagellates were observed. The cell density of diatoms and dinoflagellates were ranged from 7.0x103-2.3x105 cells L-1 and 1.3x102-6.1x104 cells L-1. The abundance of diatoms and dinoflagellates were higher in neap tide than that in spring tide. Diatoms were increased from neap to intermediate tides and it depleted in spring tide. Dinoflagellates were decreased from neap to spring tides. Additionally, diatoms and dinoflagellates abundances were increased from downstream to mid lower-estuary and decreased in the upstream. Salinity and turbidity led to increase from neap to spring tide while the diatoms and dinoflagellates distribution decreased oppositely. The present study indicated that salinity, turbidity and mixing driven by the neap-spring tidal cycle were the influencing factors for the phytoplankton distribution in a tide-dominated estuary.
Year: 2020