Aquatic Insects as Bioindicators of Water Quality in the Achenkovil River, Kerala, India.

The origin of the Achenkovil River, the Devarmalai of Western Ghats, is within the Konni reserve forest of Pathanamthitta district, flowing through Pathanamthitta, Kollam, and merging with the Pamba river in the Alappuzha district. This study included the spatial variation of aquatic insect fauna with respect to water quality. The bottom water samples and insect fauna were collected bimonthly using a Niskin sampler and D-frame nets for a period of one year (February 2019 to January 2020). The study yielded 10736 insect fauna under 8 orders, 21 families, 35 genera, and 36 species. How the quality of the water affects biodiversity of aquatic insects was examined using multivariate statistical techniques (PCA and CCA) and Pearson's correlation coefficient. The findings showed that the upstream portion of the river has a remarkable diversity and quantity of aquatic insect species. The major insect group in the collected sample was ephemeroptera. There were no pollution-sensitive taxa in the middle stream or downstream portions of the river, which suggests that the water quality was declining. The middle stream and downstream sections of the river did not contain any pollution-sensitive taxa, indicating deteriorating water quality. Human-caused factors like washing, cleaning cars, and washing cattle and disposal of garbage are common in these regions. Because most aquatic insects are sensitive to environmental fluctuations, they can be used as an efficient tool in biomonitoring studies.