Cladocerans and copepods as bioindicators of aquatic ecosystem health: Ecological roles, anthropogenic stressors and limitations

Cladocerans and copepods are dominant crustacean zooplankton groups that play central roles in aquatic ecosystem functioning. As primary consumers, they regulate phytoplankton biomass, facilitate nutrient recycling, and transfer energy to higher trophic levels, particularly fish and macroinvertebrates. Owing to their short life cycles, high sensitivity to environmental variability, and measurable population responses, these organisms have been widely used as bioindicators of water quality and ecosystem health. This review synthesizes peer-reviewed literature on the ecological roles of cladocerans and copepods in freshwater and marine systems, examines their responses to major anthropogenic stressors, including pollution, eutrophication, climate change, and habitat modification and evaluates their applicability and limitations as bioindicators. Evidence indicates that changes in abundance, community composition, reproductive traits, and functional diversity of these zooplankton groups often reflect alterations in nutrient status, contaminant exposure, and climatic conditions. However, their use as indicators is constrained by factors such as short generation times, high seasonal variability, and context-dependent responses. By integrating ecological function with indicator performance, this review highlights both the strengths and limitations of cladocerans and copepods for aquatic biomonitoring and emphasizes the need for system-specific, high-frequency monitoring frameworks.