Abstract

Plastics contaminate the oceans worldwide. Microplastics are defined as plastic particles with a size comprised between 2 μm and 5 mm. While the contamination by microplastics of seawater and fish has been well documented, the contamina-tion of corals has only been demonstrated in vitro. However, corals are key organisms in reef ecosystems and their contami-nation by microplastics could represent a critical threat for this environment, justifying an assessment of that pollution in reef habitats. In Guadeloupe (Lesser Antilles), three sites have been studied to evaluate the level of contamination of Scleractinian corals by microplastics. They were located on the East (windward), West (leeward) and North coasts of the island in order to encompass different marine conditions. In each site, three coral colonies belonging to four coral species were collected: Agaricia agaricites, Siderastrea siderea, Porites astreoides and Orbicella faveolata. Living tissues of each sample were dissolved using hypochlorite sodium. Then, microplastic particles were sorted under a binocular microscope and photo-graphed. Image processing was used to count the number of particles of plastics found inside each coral colony and to sort them according to their morphology (fragment, fiber…). Globally, 87.5 % of the sampled colonies contained microplastics, with a varying proportion of fragments and fibers according to species and sites. The size of the polyps was not significantly related to the level of contamination of the polyps. The site presenting the less contaminated corals appeared to be the most exposed to open oceanic waters and relatively sheltered from coastal anthropogenic activities. This preliminary study has revealed the importance of the contamination of Caribbean reef corals by microplastics.

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