Tire wear particles (TWP) are a major source of microplastics in the environment. Despite their prevalence, the effects of tire particle leachates on marine microplankton communities remains poorly understood. In this study, we assessed the acute impacts of tire particle leachates on the structure of coastal microplankton assemblages from the Canary Islands. Five laboratory experiments were conducted, exposing microplankton to a range of leachate dilutions over 72 h, with TWP leachates prepared from an initial concentration of 1 g L⁻¹ .Our results revealed that the abundances of diatoms, most dinoflagellates, and ciliates were significantly reduced following exposure to leachates, with median effective concentrations (EC