Metabolic modeling of daphnia for environmental toxicity studies

Daphnia, a genus of small planktonic freshwater crustaceans commonly referred to as "water fleas," plays a critical role in aquatic ecosystems and has long served as a model organism in ecotoxicological studies. Owing to its sensitivity to pollutants, short life cycle, ease of laboratory cultivation, and transparent body, Daphnia pulex has become a widely adopted test species for acute and chronic toxicity assessments. As a heterotrophic organism, Daphnia's growth and survival are highly dependent on food availability and quality, particularly essential nutrients such as phosphorus, polyunsaturated fatty acids (PUFAs), and sterols. Among various feed sources, Chlorella vulgaris has demonstrated considerable nutritional value for Daphnia cultivation, exhibiting high protein content and the ability to effectively remove selenium from wastewater. In this study, a genome-scale metabolic model of Daphnia pulex was constructed using the COBRA Toolbox within MATLAB, enabling simulation of its metabolic behavior under different nutrient conditions. The model was employed to evaluate the organism's growth response to various dietary inputs and to identify key metabolic pathways involved in nutrient assimilation. In the final stage, toxicological assessments were carried out by integrating metal concentration data from Lake Beyşehir with the metabolic model. Heavy metal compounds commonly found in freshwater environments were analyzed in terms of their potential impact on Daphnia's metabolic performance. The study presents a comprehensive framework that combines metabolic modeling with toxicological evaluation, offering novel insights into the metabolic adaptability of Daphnia pulex under both nutrient-driven and chemically stressed conditions. The results support the potential use of this integrated modeling approach for predicting the ecological consequences of pollutant exposure and assessing algal-based feed viability in contaminated water systems.