Zooplankton sebagai Bioindikator Kualitas Perairan di Sungai Krueng Langsa

River quality will change according to environmental developments. This research aims to determine the diversity of zooplankton and the role of zooplankton as a bioindicator of water quality and environmental conditions of the Krueng Langsa River. This research was carried out from February to August 2023 at 3 research locations located in the villages of Kemuning Hulu, Kampung Tengoh and Cinta Raja, East Langsa using the purposive sampling method. The results of research in the Krueng Langsa River obtained 10 types of zooplankton, namely Oncaea sp., Mesopodopsis larvae, Temora turbinata, Cyphonautes larvae, Cephalodella forticata, Cephalodella megalocephala, Keratella sp., Lecane lunaris, Rotaria neptunia and Synchaeta sp. The diversity index is in the low to medium category with an H' value of 0.41 to 1.41, the uniformity index is in the medium to high category with an E value of 0.57 to 0.88 and the dominance index is in the low category. to high with a C value of 0.28 to 0.76. Based on the abundance of zooplankton, the waters of the Krueng Langsa River are classified as oligotrophic. Environmental conditions in the Krueng Langsa River are still tolerant to zooplankton life.