摘要：Plankton is a fundamental part of the waters, especially in coral reef ecosystems. This study aims to determine the abundance and diversity of plankton species, both phytoplankton, and zooplankton in the waters of Gosong Island, Southwest Aceh. This research was conducted in May 2021. Samples of plankton were collected from 4 sampling points with 4 replications. Phytoplankton consists of 51 species which are in 3 families, namely Cyanophyceae, Bacillariophyceae, and Dinophyceae. There are 17 species of zooplankton consisting of 7 families, namely Protozoa, Crustaceans, Urochordata, Polychaeta, Gastropods, Pelecypods, and Nematodes. The total abundance of phytoplankton ranged from 292,826 to 2,661,738 cells/m3, while the total abundance of zooplankton ranged from 4,957 to 32,870 ind/m3. The composition of the presence found at the study site was found to be higher in Cyanophyceae than Bacillariophyceae and the lowest number was found in Dinophyceae. Zooplankton is found in large to low numbers in the Crustacea, Protozoa, Urochordata, Gastropod, Pelecypoda, Polychaeta, and Nematoda. This research is able to provide an initial description of diversity, abundance, and several biological indices for follow-up research. Gosong Island is an island that has coral reefs, so it is necessary to carry out routine monitoring related to the type and abundance of plankton regularly.
