Evidence of plastics integrating the geological cycle: plastic forms in coastal ecosystems along the southern Brazilian shoreline

Abstract

Plastic pollution in the ocean has reached alarming levels, being found deposited on the seafloor, floating on the water column, or stranded in beaches. It has been reported in the atmosphere, hydrosphere, biosphere, and lithosphere, forming new sedimentary rocks assuming the appearance of rocky material after being burned, cooled, and transported. Here, we report the first occurrence of plastiglomerates (Pgl) and plastistones (Pst) on the continental shoreline of Brazil, and the first record in a coastal lagoon ecosystem worldwide is reported in the present study. In total, one Pgl (Pgl1) and three Pst (Pst1, Pst2, and Pst3) were macro- and microscopically described according to their components and characteristics, and polymers were identified using near-infrared hyperspectral imaging (HSI-NIR). Pgl1 showed bivalve shells, metal, and wood as its framework and melted plastic as its cement and matrix. Vesicles (0.5-10 mm) could be observed. Plastistones showed different shapes, textures, roundness, sphericity, and encrusted bryozoans. Pgl1 (margins of a coastal lagoon) consisted of polyethylene (PE) and polyethylene terephthalate (PET). Pst1 and Pst2 (sandy beach) consisted of polypropylene (PP) and polystyrene (PS), respectively. Finally, Pst3 (sandy beach) consisted of PS, PE, and PET. The results highlight that human-caused pollution is becoming part of the geological record and reinforces the inclusion of novel plastic debris forms in marine pollution monitoring programs worldwide.