RESUMO
Potholes are microhabitats in riverine ecosystems that substantially contribute to the unique regional faunal diversity and community composition. Investigations on the ecological status of potholes in riverine habitats are very scanty. The present work is of utmost importance, particularly as a pioneering study to evaluate the health status of riverine potholes using aquatic insects as potential biological indicators. Samples of water and aquatic insects were collected and analyzed during the pre-monsoon season from February 2022 to May 2022 in the potholes at Athirappilly and the Ezhattumugham regions of the Chalakudy river basin. The present study identified 208 individuals represented by 15 families in the potholes at Athirappilly, whereas 94 individuals belong to 10 families at Ezhattumugham. The computation of water quality parameters and benthic metrics revealed a significant variation between the stations. Spearman correlation analysis revealed that the water temperature, electrical conductivity, dissolved oxygen concentration, and biochemical oxygen demand were influencing the distribution of aquatic insects in the potholes. Families such as Perlidae, Ephemeridae, Baetidae, Stenopsychidae, and Hydropsychidae (sensitive families) reported from the well-oxygenated potholes at Athirappilly, where the water temperature and biochemical oxygen demand were minimum. The significantly high percentage composition of Ephemeroptera, Plecoptera, and Trichoptera taxa and a low family biotic index value indicate good health condition of the potholes at Athirappilly. In contrast, the low percentage composition of Ephemeroptera, Plecoptera, and Trichoptera taxa and high family biotic index values, with the abundance of tolerant families (Micronectidae, Caenidae, and Chironomidae), reflect the impact of organic pollution at Ezhattumugham.
