Polycyclic aromatic compounds (PACs), including harmful polycyclic aromatic hydrocarbons (PAHs) and more toxic derivatives, are continuously released contaminants. Their provenance and dynamics in coastal oceans remain poorly understood. This study presents the first comprehensive assessment of PACs in coastal oceans by combining their presence with key hydrological and biogeochemical indicators, and potential microbial degradation. High concentrations of Σ