Biodiversity and abundance of aquatic insects in two freshwater lakes of Mysore district, Karnataka, India

Abstract

A study on aquatic insects biodiversity and abundance along with physicochemical parameters of two lentic water bodies (Varuna and Dalvoy) of Mysore district was carried out on monthly basis from October 2018 to March 2019. A total of 31 species belonging to 19 families and 6 orders were recorded during the study period. At order level, Coleoptera showed maximum relative abundance (57%) followed by Hemiptera (13%) in Varuna Lake, while in Dalvoy Lake, the order Hemiptera (66%) was most abundant, followed by Coleoptera (16%). Computation of dominant status of different species of aquatic insects in lakes based on Engelmann's scale revealed that Canthydrus laetabilis and Gyrinus distinctus, from the order Coleoptera, were dominant in Varuna Lake, while two Hemipteran species, Diplonychus rusticus and Anisops sp., were dominant in Dalvoy Lake. The highest Shannon diversity index (2.803) and evenness values (0.66) were recorded in Varuna Lake, which was slightly greater than Dalvoy Lake (2.028 and 0.45). Similarly, the Biological Working Party Score (BMWP) and Average Score Per Taxon (ASPT) values were 80 and 5.33 in Varuna Lake and 53 and 4.08 in Dalvoy Lake. This indicates Varuna Lake is less polluted and has higher species diversity than Dalvoy Lake. In terms of the physico-chemical properties of water, a significant difference was noted in electrical conductivity, total dissolved solids, free carbon dioxide, dissolved oxygen, total alkalinity, hardness, nitrate, sulphate, and chloride concentrations between Dalvoy Lake and Varuna Lake. The results of physicochemical analysis and diversity indices suggest stressed and disturbed water quality conditions at Dalvoy Lake.

Keywords

• aquatic insects
• abundance
• bio indicator
• diversity
• water quality