Journal of Marine Science and Engineering Article Shifts in Diatom Dominance Associated with Seasonal Changes in an Estuarine-Mangrove Phytoplankton Community Fareha Hilaluddin 1, Fatimah Md. Yusoff 2,3,* and Tatsuki Toda 4 1 Laboratory of Marine Biotechnology, Institute of Bioscience, Universiti Putra Malaysia (UPM), Serdang, Selangor 43400, Malaysia;
[email protected] 2 International Institute of Aquaculture and Aquatic Sciences, Universiti Putra Malaysia (UPM), Port Dickson, Negeri Sembilan 71050, Malaysia 3 Department of Aquaculture, Faculty of Agriculture, Universiti Putra Malaysia (UPM), Serdang, Selangor 43400, Malaysia 4 Laboratory of Restoration Ecology, Faculty of Engineering, Soka University, 1-236 Tangi-cho, Hachioji, Tokyo 192-8577, Japan;
[email protected] * Correspondence:
[email protected] Received: 6 June 2020; Accepted: 13 July 2020; Published: 17 July 2020 Abstract: A study on seasonal phytoplankton abundance and composition in a mangrove estuary, Matang Mangrove Forest Reserve (MMFR), Malaysia, was carried out to determine the phytoplankton structure in this ecosystem, and to identify potential indicators of environmental changes. Phytoplankton samples were collected bimonthly from June 2010 to April 2011, to cover both dry (June to October) and wet (November to April) seasons, at four selected sampling sites along the river. Diatoms showed the highest number of species (50 species) from a total of 85 phytoplankton species from 76 genera. Diatoms contributed more than 90% of the total phytoplankton abundance during the dry season (southwest monsoon) and less than 70% during the wet season (northeast monsoon) as dinoflagellates became more abundant during the rainy season. Two diatoms were recorded as dominant species throughout the sampling period; Cyclotella sp.