MACROZOOBENTHOS ROLE AS A BIOINDICATOR OF QUALITY IN BILAH RIVER LABUHANBATU

Bilah River is the largest river in Labuhanbatu District, Sumatera Utara Province. Many community activities, such as sand mining, local water companies, agriculture, fisheries, transportation, palm oil mills and source of drinking water occurred in this river area. The research was conducted for 12 months from December 2016 to October 2017. The analysis result of water quality in the upstream of Bilah river (stations 1, 2 and 3), were classified as good quality; stations 4, 5 and 6 as medium quality; while the downstream (stations 8, 9 and 10) were classified as not good. Two phylas, 4 classes, 11 orders, 20 families and 27 species of macrozoobenthos were obtained. The insect class is the mostly found group in the sampling location consisted of 19 species. Diversity Index values ranged from 0.9872-2.441 and the Biotic Index value ranged from 0-15. Bioindicator species in the upstream were of orders: Coleoptera (Psephenus texanus), Ephemeroptera (Heptagenia diabasi), Plecoptera (Neoperla sp, Swelstsa sp) and Trichoptera (Chimarra sp). In the moderate polluted part of the river, bioindicator macrozoobenthos were of orders: Odonata (Aphylla angustifolia, Ceriagrion tenellum, Macrodiplax balteata, Macromia illinoiensis). Furthermore, bioindicator species in the downstream with heavy pollution were Gastropoda (Pleurocera canaliculate).