SAMIKSHA AGARWAL AND SALTANAT PARVEEN
Abstract
Cladoceran species are small planktonic crustaceans and are widely used as effective bioindicators of the trophic status of aquatic systems. Their short life cycle, sensitivity to environmental stressors, and their key position in the aquatic food web make them highly responsive to variations in water quality and biological interactions. This study aimed to explore the role of cladoceran species, viz., D. pulex and M. macrocopa, as a bioindicator of aquatic pollution by incorporating a field study with laboratory analysis. These microcrustaceans exhibit distinct sensitivities to changes in water quality parameters, including temperature, nutrient concentrations, dissolved oxygen levels, pH, and the presence of toxic substances such as pesticides. Combining bioassessment of cladoceran species with physicochemical analysis provides useful insights into the trophic status of water bodies. Laboratory experiments measured the lethal concentration (LC50) and monitored sublethal effects like clutch size, population size, and survival during controlled pesticide exposure. Parallel field studies were conducted in both pesticide-affected and reference aquatic environments to evaluate population dynamics, species diversity, and their relationships with physicochemical factors. The findings indicated that D. pulex demonstrated greater sensitivity to contaminants, characterised by lower LC50 values and significant reproductive suppression, while M. macrocopa exhibited a comparatively higher tolerance but displayed alterations in population structure in response to field conditions. The integration of lab and field findings confirmed that laboratory assays provide precise toxicity thresholds, while field studies validate ecological relevance under complex, multi-stressor environments. The integrated approach emphasises the importance of utilizing cladoceran species as complementary bioindicators, with D. pulex acting as an early-warning species and M. macrocopa indicating wider ecological effects.