Seasonal Variations in the Abundance and Characteristics of Microplastics in the Coatzacoalcos Beach Sediments, Southwestern Gulf of Mexico

Microplastic pollution has become a growing concern in coastal ecosystems, due to its persistence and potential ecological impacts. This study evaluates the seasonal differences in microplastic abundance in the Coatzacoalcos beach sediments, Veracruz, Gulf of Mexico. Sediment samples were collected from the foreshore zone during the dry (April 2019) and rainy (October 2022) seasons. Microplastics were extracted by density separation and analyzed using Stereomicroscopy, Scanning Electron Microscope (SEM), and Fourier-Transform Infrared Spectroscopy (FTIR). The microplastic abundance estimation was higher in the rainy season (1210 MPs kg−1) compared to the dry season (690 MPs kg−1). Polymers detected during the rainy season were acrylonitrile–butadiene–styrene (ABS), poly(ethyl acrylate) (PEA), and cellophane (CE). The surface features of microplastics in the rainy season exhibited smooth surfaces, physical weathering features, adhered silica globules, and fragments of diatom frustules, indicating biological colonization and recent deposition after a long marine transport. In the dry season, the identified polymers were styrene–acrylonitrile (SAN), ABS, PEA, and CE, with surface features dominated by chemical weathering, such as flaking, dissolution pits, and grooves due to photo-oxidation. Seasonal variability in microplastic distribution was influenced by precipitation, river discharge, and sea currents. These findings highlight the role of climatic factors in controlling microplastic abundance, and highlight the need for improved waste management strategies in the coastal regions.