Marine ecotoxicity of polystyrene microplastics, imidacloprid, and acyclovir: individual exposure in microalgae, rotifers and crustaceans

Marine ecosystems are increasingly exposed to emerging pollutants such as pharmaceuticals, pesticides, and microplastics, raising concerns over their potential ecological impact. This study investigated the eco-genotoxic effects of the antiviral drug acyclovir (ACV), the pesticide imidacloprid (IMD), and 1.0 μm polystyrene microplastics (PS-MPs) in representative marine organisms from different trophic levels: the microalga Phaeodactylum tricornutum, the rotifer Brachionus plicatilis, and the crustacean Artemia franciscana. Ecotoxicity tests showed that PS-MPs were the most toxic to P. tricornutum (EC50 = 8.30 mg/L), followed by IMD (EC50 = 135.83 mg/L) and ACV (EC50 = 177.83 mg/L). Among consumers, B. plicatilis was more sensitive to PS-MPs and ACV (LC50 ∼100 mg/L). PS-MPs showed the lowest short-term toxicity in A. franciscana (<20 % lethality at 200 mg/L). Genotoxicity was observed starting from 20 mg/L for IMD, 2 mg/L for ACV, and 0.2 mg/L for PS-MPs, the latter being the most environmentally concerning. Environmental risk assessment indicated no immediate ecological threat from IMD and PS-MPs at current marine environmental concentrations.