Ecotoxicological Effects of Diclofenac (Voltaren) on physiological Performance and Cellular Integrity of Two Green Microalgae "Tetradesmus obliquus and Nannochloropsis oculata”

Abstract

Pharmaceuticals are designed to produce specific effects in the body, even at very low doses. However, due to their widespread use and the inability of most wastewater treatment plants to completely remove them, traces of these compounds are now commonly detected in rivers, lakes, and other aquatic environments. In this study, we investigate the effects of Voltaren, a widely used anti-inflammatory drug, on two green microalgal species, Tetradesmus obliquus and Nannochloropsis oculata, which are essential primary producers in aquatic food webs. Exposure to different concentrations of Voltaren (LC₁₀, LC₂₅, and LC₅₀) resulted in significant growth inhibition in both species. After 24h of exposure at LC₅₀, cell densities decreased by 76.5% in T. obliquus and 57.6% in N. oculata. Chlorophyll a content also declined sharply after 96h, decreasing by 87.4% in T. obliquus and by 82.9% in N. oculata, even at the lowest concentration. Biochemical analyses revealed marked reductions in cellular components: T. obliquus exhibited decreases of 20% in protein, 59.5% in carbohydrates, and 57.4% in lipids, whereas N. oculata showed greater reductions of 51.2%, 64%, and 62.5%, respectively. Transmission electron microscopy (TEM) revealed severe ultrastructural damage in algal cells exposed to Voltaren. These findings demonstrate that even low concentrations of pharmaceuticals can significantly impair algal physiology and morphology, potentially disrupting aquatic ecosystem stability. The results emphasize the need for stricter environmental risk assessments of pharmaceuticals and for integrating ecological safety into drug design, usage, and wastewater management strategies.