Toxicity of tyre wear particle leachates to marine phytoplankton

•TWP leachates have a negative effect on phytoplankton growth.•EC50 values range from 23 to 64% concentration of leachates from 1 g L−1 TWP.•The dinoflagellate H. steinii was the most sensitive studied species to TWP leachates.•Potentially environmentally relevant effects in coastal areas after road runoff. Tyre wear particles (TWP) are some of the dominant sources of microplastics in the aquatic environment. Once TWP enter aquatic systems, they can leach certain plastic additives that can be potentially toxic to biota. However, little is known about the impact of TWP lixiviates on marine phytoplankton, the base of marine food webs. This study aims to determine the acute toxic effect of leachates derived from TWP on three phytoplankton species: the cryptophyte Rhodomonas salina, the diatom Thalassiosira weissflogii and the dinoflagellate Heterocapsa steinii, using the median effect concentration (EC50) for specific growth rate as endpoint. Leachates were obtained by incubating 1 g L−1 of