Short-term ingestion and tissue incorporation of Polystyrene microplastic in the scleractinian coral Porites porites

Abstract

Microplastics (MP), plastic fragments whose diameter is less than 5 mm, are an emergent pollutant in marine environments. Benthic organisms, such as corals, are at high risk of suffering toxic effects due to MP exposure. This study aims to evaluate the incorporation of polystyrene microparticles (PSm) on the reef building coral species Porites porites. PSm were synthesized employing the simple emulsion and solvent evaporation technique, obtaining round particles with a diameter of ≤5μm. P. porites fragments were exposed to four different PSm concentrations (1, 10, 100, 1000) mg/L over a period of 96 h. Histological techniques were used to evaluate PSm incorporation. No mortality was recorded during the bioassay. PSm incorporation in the gastrovascular cavity was evidenced in all of the tested concentrations. Additionally, in the highest PSm concentration (1000 mg/L), clusters were detected inside the gastrovascular tissue and mesenterial filaments. As complementary information, no statistically significant differences were found across PSm concentrations for catalase enzymatic activity and melanin content (PERMANOVA based on Euclidean distances) as a proxy of general exposure effects. This study found that P. porites is capable of ingesting microplastics, specifically polystyrene microspheres regardless of the tested concentrations, without presenting apparent toxic effects in a 96-hour exposure period. Moreover, it is shown that PSm can be incorporated inside the coral tissue. Further studies are needed to assess the potential toxic effects of MP ingestion with longer exposure times, as well as the possible mechanisms involved in MP recognition and incorporation.