Effects of Sodium Diclofenac on Daphnia magna: Growth, Locomotion, Heartbeat and Risk Assessment

As the population of large urban centers grew following major world revolutions, the consumption of pharmaceuticals increased. Consequently, these substances are frequently detected in water treatment plants, surface waters, and even sediments. Sodium diclofenac (DCF), a non-steroidal anti-inflammatory drug (NSAID), can cause adverse effects on organisms when released into the environment, particularly in aquatic ecosystems. This study aimed to assess the acute and chronic effects of DCF exposure on Daphnia magna. The organisms were exposed to nominal DCF concentrations for 48 hours (acute exposure) and 21 days (chronic exposure). The evaluated endpoints for acute exposure included EC₅₀ (48h), NOEC, LOEC, and risk quotient (RQ). For chronic exposure, survival, body length, reproduction, and behavioral parameters (locomotion and heart rate) were analyzed. The EC₅₀ (48h) value was determined as 42.47 mg L⁻¹, indicating a high environmental risk (RQ = 3.91). The LOEC value obtained in acute exposure resulted in 100% mortality within the first 10 days of prolonged exposure. The length (cm) of exposed organisms decreased with increasing concentrations. Reproduction was affected only in terms of the number of neonates at 3.75 mg L⁻¹. Locomotion and trajectory were impaired at 0.0375 mg L⁻¹, while heart rate increased with rising DCF concentrations, with effects observed from the lowest concentration tested (0.00375 mg L⁻¹). This study highlights the toxicological effects of DCF on the freshwater organism D. magna. Given the widespread use of DCF, further studies across different trophic levels are necessary to support discussions on its regulation and potential inclusion in Brazilian and international regulatory frameworks.