Dispersão de microplásticos em águas superficiais e sedimentos de fundo da plataforma continental de Fortaleza

Plastic products are widely used worldwide, with their production increasing steadily since the 1950s. The emergence of microplastics (MPs), small plastic debris measuring <5 mm, has become a widespread problem in marine environments. These particles enter the marine environment from various land and marine sources, causing harm to marine organisms. Plastic pollution predominates in marine debris (60-85%). The study of microplastic pollution in aquatic ecosystems has grown in the last decade, including in Brazil, but there is little information on the dispersion, deposition, and accumulation of MPs in the coastal waters of Fortaleza. This research aims to compare seasonal variations in the amount of microplastics and perform the morphological and chemical characterization of water and sediment samples collected off the coast of Fortaleza, Ceará. Surface water samples were collected using a plankton net (0.33 mm mesh) and bottom sediment samples were collected using a Van Veen dredge in five areas off the coast of Fortaleza (the mouth of the Cocó River, Maceió Stream, submarine outfall, storm drain, and the mouth of the Ceará River). The samples were taken to the laboratory where they were separated, processed, and analyzed. 2,742 MPs > 0.3 mm and 977 MPs < 0.3 mm were found in the water samples, and 1,466 in the sediment samples, considering all samples. The presence of particles was greater than 90% in all samples and areas. Fibers were the most common form at all sites, while red and blue colors were present in 100% of the samples. The total masses for water samples in April were 16.05 g of MPs > 0.3 mm and 8.92 g of MPs < 0.3 mm. In November, they were 42.13 g and 36.43 g, and in January, 19.31 g and 15.44 g, respectively. The area with the highest concentration of microplastics was at point C10 and points E16, E17, and E18, indicating a possible source of release. The region with the lowest concentration was the mouth of the Ceará River. Concentrations varied between the months, with the highest concentrations in April in the drainage areas, in November at the mouth of the Cocó River and drainage points, and in January in the drainage and Barra do Ceará. However, there was no statistical difference (95% significance) in the sediment samples between the dry and rainy seasons. Regarding polymer composition, 77% was polyethylene and 23% polyethylene. Therefore, the significant presence of microplastics was revealed in the waters and sediments off the coast of Fortaleza, Ceará, with some seasonal variations in concentrations. Over 90% of the collected samples contained microplastics, highlighting the worrying spread of these materials. The analysis identified a predominance of polyethylene and polypropylene, highlighting the need for continuous monitoring and management strategies to mitigate pollution. The seasonal patterns suggest complex environmental influences, requiring further studies to better understand and plan for the protection of marine ecosystems.