Struktur Komunitas Plankton dan Kaitannya dengan Siklus Pasang Surut di Perairan Estuari Belawan Provinsi Sumatera Utara

Abstract

Belawan Estuary is one of the estuary areas or the east coast of Sumatra which has a distinctive and complex ecosystem with various habitat types. The measurement of tidal time has an effect on the composition of plankton species. This research was conducted from October to December 2023 at the Belawan Estuary. The purpose of this study is to determine the structure of plankton communities during tides and their distribution in the Belawan Estuary. Determination of sampling location using purposive sampling method at 8 observation stations by following 4 phases of tidal cycle. Plankton samples were taken using the horizontal method by tying plankton nets on the ship, then the ship was run for 20 minutes. The results of plankton identification found at high tide and at low tide were 16 classes of plankton with a total of 64 species. For phytoplankton, 60 species were obtained which were divided into 9 classes, namely Bacillariophyceae, Chlorophyceae, Conjugatophyceae, Coscinodiscophyceae, Cyanophyceae, Dinophyceae, Euglenoidea, Mediophyceae and Prymnesiophyceae. While zooplankton obtained 14 species divided into 7 classes, namely Chromadorea, Clitellata, Crustacea, Eurotatoria, Foraminifera, Oligohymenophorea and Spirotrichea. The highest diversity of the class Bacillariophyceae (23 species) dominated by Skeletonema sp. The highest abundance spatially and temporally was found at station 5 low tide and the first quarter phase of low tide with the amount of phytoplankton abundance of 75371.4 cells / L, and zooplankton 118150 ind / L with the highest saprobic values of -3 spatially and -2.74 temporarily. This value shows that the Belawan Estuary is heavily polluted. The relationship of chemical physical parameters with plankton abundance and diversity tends to be influenced by currents, TSS, DO, salinity, water table height.