Evaluation of trophic state conditions in the three urban perennial lakes of the Coimbatore district, Tamil Nadu: Based on water quality parameters and rotifer composition

Abstract

This study aims to examine the trophic state conditions in the three major urban perennial lakes of the Coimbatore district based on the physicochemical properties and rotifer community structure. The study was conducted for a period of three months, from January 2023 to March 2023. The water and plankton samples were collected twice a month. The measured physicochemical properties showed that pH, salinity, total hardness, nitrate, and phosphate were found to be higher in Kumarasamy lake, followed by Ukkadam and Valankulam lake ecosystems. The higher rotifer population density was observed in Valankulam lake (1820 Ind./L), and lower in Kumarasamy lake (1080 Ind./L). In this study, Brachionidae species were abundantly found in the three perennial lake water environments, followed by Asplanchnidae, Lecanidae, Trichocercidae, and Filiniidae. In addition, a total of 28 freshwater rotifer species were reported for the first time from the three perennial lakes of the Coimbatore district, respectively. The determined trophic state index (TSI) (47.57) and rotifer trophic state index (TSI_ROT) (51.25) values affirm that the three perennial lakes are under meso-eutrophic conditions. The examined diversity indices values revealed that species dominance (D) and species richness (SR) are higher in Valankulam lake, followed by Ukkadam and Kumaraswamy lake ecosystems. This difference may be due to the influence of human activities and the mixing of various points and non-point sources of pollutants. The present study concluded that the three perennial lakes were moderately polluted by various sources of pollutants; therefore, continuous monitoring is needed for the conservation of flora and fauna diversity in the three perennial lakes of the Coimbatore district.