This study aims to evaluate effects induced by the exposure of key marine species to leachates and suspensions of different particle-size of PET microparticles, a plastic polymer that is actually considered safe for the environment. Leachates and suspensions of small (5–60 μm); medium (61–499 μm) and large (500–3000 μm) PET were tested on bacteria (V. fischeri; UNI EN ISO 11348-3:2009), algae (P. tricornutum; UNI EN ISO 10253:2016E), and echinoderms (P. lividus; EPA 600/R-95-136/Section 15) species both under standard (8.0) and acidified (7.5) pH conditions. Results obtained show that: i) conversely to larval stage of P. lividus, bacterial and algal tested species are not sensitive to PET pollution under all tested conditions; ii) different tested particle-sizes of PET produce effects that are not always related to their particle-size; iii) differences comparing acidified and standard pH conditions were recorded; iv) concerning echinoderms, food availability produce significant differences compared to fasting conditions; v) special attention on the possible interactions between MPs and other stressors (e.g., food and pH) is needed in order to give a better picture of natural occurring dynamics on marine ecosystems especially in the future frame of global changes.
