Research Article

Stable Isotopes in Freshwater Zooplankton Ecology: Tracing Trophic Dynamics and Environmental Change

Abstract

Stable isotopes of carbon (δ13C) and nitrogen (δ15N) are pivotal in aquatic food web studies, serving as intrinsic tracers of carbon sources and trophic positioning. In freshwater ecosystems, zooplankton represent an essential intermediate trophic group, rapidly integrating isotopic signals from lower trophic levels. This mini-review critically examines the current state of knowledge regarding stable isotope applications in freshwater zooplankton research, with a focus on quantifying anthropogenic impacts such as eutrophication, land-use conversion, and climate-mediated hydrological shifts. The review synthesizes key empirical findings, methodological protocols, and statistical approaches for interpreting isotopic variability. Recent advancements in compound-specific isotope analysis (CSIA), baseline normalization, and mixing models are discussed. Emphasis is placed on tropical and subtropical regions, including South Indian aquatic systems, where isotopic frameworks remain underutilized. This synthesis highlights the potential of stable isotope techniques to elucidate biogeochemical pathways, refine ecosystem models, and support biomonitoring under accelerating global change.