Contamination of Seston and Sediments in the Colombian Caribbean by Polycyclic Aromatic Hydrocarbons

The widespread expansion of human activities has increased contamination in marine ecosystems, particularly by polycyclic aromatic hydrocarbons (PAHs), which threaten ecosystem functioning and biodiversity. Known for their adverse effects, many PAHs are carcinogenic and mutagenic, posing an important health risk. Nevertheless, substantial knowledge gaps persist regarding the occurrence of PAHs in the seston and sediments of tropical estuaries across many regions worldwide. Therefore, this study aimed to (a) determine PAH concentrations in seston and sediments during rainy and dry seasons and (b) assess contamination risks in the Colombian Caribbean. Samples from 10 locations, collected in November 2021 and April 2022, were analyzed using gas chromatography–mass spectrometry. Results showed the highest PAH concentrations in seston during the rainy season, reaching 4,428.7 ng g −1 in the Magdalena sector of Ciénaga Grande de Santa Marta and averaging 2,641.3 ± 861.6 ng g −1 (ranging from 1,421.4 to 3,735.1 ng g −1 ) in the Sinú sector. In sediments, the highest concentrations were found in the Sinú sector during the dry season, averaging 2,870.5 ± 3,218.3 ng g −1 (ranging from 886.4 to 8,557.8 ng g −1 ). Salinity, organic matter, and silt were significantly associated with the distribution of high-molecular-weight PAHs, likely because these factors influence flocculation and sedimentation rates. Although PAH levels were within US Environmental Protection Agency limits, sediment quality indices (e.g., mean effects range-median quotient and mean probable effects level quotient) indicated moderate contamination levels, suggesting potential biological effects. The study identifies priority hotspots for targeted monitoring and follow-up ecological assessment, with the aim of protecting regional biodiversity and food security.