Water Quality Assessment with Biotic Index Based on Abundance and Diversity of Aquatic Insects in a Hilly Stream, Bangladesh

Abstract

Study of stream insect fauna provide valuable insights into aspects of the stream channel ecosystem. The present study was conducted to investigate the aquatic stream living insect community, abundance and diversity in a hilly stream, Balukhali chora of Chittagong University campus to determine the water quality. The insects were collected with bottom dredge net from the edge and benthic regions of the Riffle zone and the Pool zone of the stream from January 2018 to December 2018. Insects were sampled using standard entomological method and determined their tolerance value. A total of 2535 insects were recorded, belonging to six insect orders, 30 families and 45 genera. The abundance ratio was higher in all the months in the Pool zone excepting the months of April, May, June and October. The orders Ephemeroptera, Odonata and Diptera were abundant in the Pool zone, while Hemiptera, Coleoptera and Lepidoptera were abundant in the Riffle zone. On the basis of Biotic Index, the most dominating orders Odonata and Hemiptera indicated good water quality, though the dipteran genus Chironomus spp. indicated poor quality in some of the months. The stream insect community structure of the two zones indicated that the overall water quality of the stream water was very good. Both manmade and natural interruption occurred in the stream channel due to human settlement, agricultural runoff and natural disasters. The study was conducted to know the abundance and diversity of aquatic insect community which indicated the water quality of the stream.