Zooplankton community structure and ecology of the Pit Lakes, Raniganj Coal Field, West Bengal, India

Abstract

Man-made pit lakes are often formed as a result of mining activities, and they can significantly alter the local ecosystem. Understanding the zooplankton community in these lakes is crucial as zooplankton play a vital role in the aquatic food chain and are sensitive indicators of water quality. The primary aim of this study is to determine the zooplankton composition and wet land zooplankton index in some pit lakes of Raniganj Coal Field (RCF) area. For three years (2023-2025), monthly samples of surface water and zooplankton were collected from 11 pit lakes. Water quality parameters like temperature, Secchi depth, dissolved oxygen, pH, conductivity, and total dissolved solids were measured on-site. Analyses for nitrate, phosphate, total hardness, alkalinity, Turbidity and chloride were conducted using standard methods. Zooplankton were collected from the subsurface layer using a 50-liter bucket and a 50 µm plankton net. 52 zooplankton species, of which nine were Cladocera, six Copepoda and 37 Rotifera. The most abundant and diverse zooplankton species were rotifers, followed by copepods. The most abundant species were: Brachionus falcatus, B. forficula, Keratella cochlearis, K. tropica, Tropocyclops sp. and Moina micrura. Redundancy analysis highlighted that pH, chloride, phosphate, turbidity, nitrate and Secchi depth were the prevailing environmental parameters. The most prevalent species was Brachionus forficula. Overall, these findings contribute to a deeper understanding of zooplankton diversity, community structure, and their relationship with environmental factors in man-made pit lakes, providing valuable information for conservation and management efforts in these unique aquatic environments.