Aquatic insects as bioindicators of stream water quality - a seasonal analysis on Western Ghats river, Muthirapuzha, in central Kerala, India

Abstract

This study was conducted to assess the water quality of Muthirapuzha River, Idukki using aquatic insects as bioindicators. Insects were collected on a seasonal basis from February 2014 to January 2015 from 12 sampling stations. Insects were sampled using standard collection methods and were identified up to family level. A total of 3,278 individuals belonging to seven orders and 37 families were collected during the study period. The greatest number of taxa was represented by order Ephemetroptera during monsoon (27%) and post-monsoon (25%), while Diptera (22.7%) dominated the pre-monsoon season. Shannon Weiner diversity index, Simpson dominance index, and Margalef’s richness index was highest post-monsoon. The EPT score in Muthirapuzha was for normal waters, however, pre-monsoon values were lowest, indicating pollution load during this period. Hilsenhoff’s family biotic index (HFBI) was used to estimate the status of organic pollution along the river based on representative families of aquatic entomofauna; values were highest at pre-monsoon season. The overall organic water quality level in the Muthirapuzha was good to fair based on this study.