Microplastic Occurrence in Relation to Sediment Granulometry Along the Central Caribbean Coast of Colombia

Previous investigations along Colombia’s central Caribbean coast have documented microplastic (MP) pollution in terms of typology, abundance, and spatial distribution. However, the influence of sediment granulometry and associated statistical parameters (mean, median, sorting, skewness, and kurtosis) on MP occurrence remains poorly understood. This study addresses this gap through an integrated assessment conducted at 15 coastal sites along the central Caribbean coast of Colombia. Sediment samples were collected and analyzed to determine granulometric characteristics and to quantify MP abundance, shapes, and potential impacts, enabling evaluation of their relationships. Grain-size distributions were broadly homogeneous among the surveyed beaches, with dominance of sand, slightly gravelly sand, and slightly gravelly muddy sand. Sorting conditions were primarily moderately well sorted (60%), followed by moderately sorted (20%), well sorted (13%), and very well sorted sediments (7%). Microplastic densities ranged from 160 to 1,120 MPs kg⁻¹, values comparable to those reported for beaches and coastal embayments worldwide. Fibres were the dominant MP typology, representing 86.8% of the total items recorded. Multiple linear regression analysis indicated that approximately 30% of the variability in MP occurrence could be explained by the sediment statistical parameters considered, with sorting emerging as the most influential variable, accounting for ~11% of the explained variance (r² = 0.27; F = 0.67). These findings highlight the role of sedimentary processes in modulating microplastic accumulation on sandy beaches. To manage the MP issue, reducing the current elevated plastic inputs into the environment is necessary/mandatory. Approaches to reach this goal must be focused on the entire plastic life cycle (extraction, design, production, use, disposal, recovery, recycling).