Uptake and effects of nanoplastics on the dinoflagelates Gymnodinoum corollarium.

Plastic nanoparticles are the final state of degradation of plastic in the environment before disintegrating into low-molecular-weight organic compounds. Unicellular organisms are very sensitive to the toxic effects of nanoplastics, as they are often capable of phagotrophy, but are unable to consume such a foreign material as synthetic plastics. We studied the effect of polystyrene, poly(vinyl chloride), poly(methyl acrylate), and poly(methyl methacrylate) nanoparticles on the photosynthetic dinoflagellates Gymnodinium corollarium Sundström, Kremp et Daugbjerg. Fluorescent tagged particles were used to visualize plastic capture by dinoflagellate cells. We found that these dinoflagellates are able to phagotrophic nutrition and thus should be regarded as mixotrophic species. This causes their susceptibility to the toxic effect of plastic nanoparticles. Living cells ingest plastic nanoparticles and accumulate in the cytoplasm as micrometer-level aggregates, probably in food vacuoles. The action of nanoplastics leads to a dose-dependent increase in the level of reactive oxygen species in dinoflagellate cells, indicating plastic degradation in the cells. The introduction of a methyl group into the main chain in the α-position in the case of poly(methyl methacrylate) causes a drastic reduction in toxicity. We expect that such nanoparticles can be a tool for testing unicellular organisms on heterotrophic feeding ability. We suggest a dual role of dinoflagellates in the ecological fate of plastic waste: the involvement of nanoplastic in the food chains and its biochemical destruction. This article is protected by copyright. All rights reserved. Environ Toxicol Chem 2023;00:0-0. © 2023 SETAC.