Taxonomic and trophic characterization of benthic macroinvertebrate fauna in headwaters of eastern Himalaya

A taxonomic and functional feeding group study of benthic macroinvertebrate fauna was conducted in the headwater streams/Kholas of eastern Himalaya viz. Rimbi Khola and its tributaries (Nambu Khola, Limbuni Khola and Lingsur Khola). Samples were collected twice in a year during January and February 2017. Standard methods were adopted for the samples collection and identification of benthic macroinvertebrate fauna. The density ranged from 264 to 792 indiv.m⁻² among Rimbi Khola and tributaries. Seventeen taxa were recorded with highest taxonomic richness in Rimbi Khola compare to the tributaries. Leptoceridae was most abundant taxa in all streams/Kholas followed by Hydropsychidae, Leptophlebidae and Baetidae. CCA identified discharge, current velocity and substratum as most important factors in streams/Kholas, while different characteristics taxa were determined by PCA. These variations in environmental variables and characteristics taxa were attributed to proximate factors in each river. However, trophic characterization indicated that all the streams/Kholas were dominated by shredders. Collectors were second most abundant trophic group in the Rimbi, Limbuni and Lingsur Khola, while scraper in Nambu Khola. Nambu Khola was different from rest of the streams due to variation in dominant trophic groups, because of open stream system and high periphytonic growth.