Introducing plasticoral: A biogenic-plastic agglutinate as an emerging indicator of the Plasticene in Okinawa reef...

Plastic pollution has become a significant concern for marine environments with adverse effects on critical ecosystems such as coral reefs. Marine plastic litter items transform into new variants after prolonged exposure to the environment and interactions with organic and inorganic materials. While earlier documented variants such as plastiglomerates and plasticrusts are chiefly formed between plastic and abiogenic substrates, this study introduces plasticorals, a new form of plastic litter variant formed from plastic materials thermally adhered to or agglutinated to coral rubble. Plasticorals were incidentally observed on three beaches in Okinawa Island, Japan, during routine marine litter surveys. The plastic components of these plastic-coral agglutinate samples, examined with Raman spectroscopy showed spectral consistencies with polyethylene and polypropylene. The infiltration of skeletal pores and plastic coral interface were visualized using micro-CT scanning and microscopy. This new plastic variant provides fresh perspectives on the persistence of plastic litter in coral reef environments and highlights the potential for plasticorals to serve as future stratigraphic markers within the contemporary sedimentary record of tropical reef systems. We recommend further studies to better understand formation processes, distribution, and potential ecotoxicological impacts of plasticorals on coral reef environments.