Characteristic and histological evidence of microplastic in scleractinian corals of Java']Java Sea

Coral reefs are threatened by emerging microplastic pollution but only a few studies are available regarding the extent of contamination in coral reef systems in situ. For this research, we collected samples from the seawater, sediments, and coral colonies of the Panjang Island cluster and the Karimunjawa Archipelago, Java Sea. Microplastics were detected in all sample types. Based on a Mann-Whitney test (p < 0.05), there is a significant difference in microplastic abundance between areas subjected to different levels of human activity. Corals showed the highest concentration of microplastics, with fragments being the most dominant type. No significant difference in microplastic abundance was found among the different polyp sizes (Mann-Whitney test, p > 0.05) or among different species (Kruskal-Wallis test, p > 0.05). All coral samples contained fragment and fiber microplastics in their polyps, consisting of Polyethylene terephthalate (PET), silicone-based plastic, polysulfoxide, and Polyvinyl alcohol (PVA) polymer. Here, we provide the first evidence of microplastics inside corals, observed using a histological method. The types of microplastic detected in the histological sections were similar to those extracted from the coral polyps. Tourism and fishing activity both play a role in governing the distribution, abundance, and diversity of microplastics in coral reef systems.