Identification and Measurement of Microplastics in Posidonia oceanica Banquettes in the Gulf of Gabes, Tunisia

Plastic pollution and microplastic (MPs) debris are some of the most significant solid waste pollutants, menacing the marine environment. However, Posidonia oceanica, an endemic Mediterranean Sea seagrass, has been revealed as an MPs’ accumulation agent. This study aims to determine the abundance, characteristics, and composition of MPs on the southern side of the Tunisian Mediterranean Sea, by using P. oceanica as a key trap for MPs. It has been realized in the frame of the MED Dé. Co. U. Plage project. Samples of P. oceanica banquettes were collected, the characterization of MPs detritus was carried out by stereomicroscopy, and acid digestion of Posidonia tissues was performed for qualitative and quantitative analysis of MPs using Nuclear Magnetic Resonance (NMR) spectroscopy. The dominant shape types of MPs in all samples were granules, filaments, and fragments. The most common colors of MPs were blue and black. Polyethylene, polystyrene, and bis 2-ethyl-hexyl phthalates were the most commonly identified polymers. P. oceanica shoots contribute to the trapping and storing of MPs, the horizontal migration on the seafloor, and the burial into sediments. Marine vegetation is a good tool to detect and track plasticizers and more studies on seagrass beds will provide researchers with a complete geographical picture of the dispersion and the rate of pollution by MPs. The results obtained will be used for developing baseline data on plastic contamination in the Tunisian marine coast.