Abstract
The existence of diatoms greatly affects the life in the water as it plays some important roles as a source of food for various organisms in aquatic ecosystems. In addition, the diatoms existence is commonly used as an environmental bioindicator. The purpose of this study was to determine the diatom community structure in the Maluk Coastal waters. The water sample was taken from three coastal waters areas by using plankton net of 20 m in size and there thirty-eight diatom species were identified. Data of diatom community were analyzed by using parameters of density, species diversity index, species evenness index, and values of importance for diatom species. The density of diatom in all sampling sites is 1600 ind./L. Five species of diatoms that have the highest density were Asteroplanus karianus (573.333 ind./L), Thalassiothrix longissima (423.333 ind./L), Striatella unipunctata (130 ind / L), Gyrosigma scalprum (50 ind / L), and Licmophora abbreviate (40 ind/L). The diversity index value of the diatom species was in moderate category (1.964). Asteroplanus karianus was a species that can be found in all three sampling sites and with the highest value of importance of 40.751%. The diatom species evenness index was 0.522, which means that the diatom species were not distributed evenly, because there were several species dominating with a large number of individuals at certain sampling sites.