Impacts of environmental pharmaceuticals on diatom physiology: Mechanistic, functional and ecological perspectives

Pharmaceuticals, a diverse class of bioactive compounds, are increasingly recognized as a significant ecotoxicological concern in aquatic environments. Their high target specificity and potency at nanomolar concentrations can disrupt evolutionarily conserved biochemical pathways in non-target organisms, even at sub-therapeutic environmental levels. Diatoms (Bacillariophyceae), as silica-walled microalgae, are ecologically indispensable yet underrepresented in ecotoxicological risk frameworks. This review consolidated findings from available empirical studies to examine the mechanistic and physiological impacts of pharmaceuticals and antibiotic mixtures on diatoms across cellular, molecular, and community scales. We assessed compound-specific toxicity profiles, concentration-response dynamics, and hormetic thresholds, as well as alterations in chloroplast photophysiology (Fv/Fm, OJIP kinetics), redox balance (reactive oxygen species and antioxidant enzymes), frustule biosilification, and lipidome remodeling. Moreover, we evaluated the potential of diatoms in phcoremediation, highlighting their capacity for pharmaceutical biosorption, biotransformation, and ecological sequestration, particularly in engineered bioreactor systems. Finally, the review stressed the need for a paradigm shift from single-compound assays to mixture toxicity modeling and multi-generational ecotoxicogenomics, aiming to capture latent evolutionary consequences of chronic exposure. By integrating diatom-based endpoints into regulatory surveillance and predictive modeling, we underscored the necessity for change in safeguarding aquatic microbial primary producers amid intensifying chemical anthropogenesis and mounting antimicrobial resistance.