ABSTRACT                      

Current understanding of the distribution, bioaccumulation, and trophic transfer patterns of polycyclic aromatic hydrocarbons (PAHs) in coral reef ecosystem remains limited, particularly regarding their potential associations with coral-associated microbial communities. This study investigated PAH occurrence, bioaccumulation, and apparent trophic distribution patterns across ecological compartments within the coral reef ecosystem of the Weizhou Island, northern South China Sea (SCS). PAHs were detected in multiple environmental and biological compartments, with zooplankton and coral tissue exhibiting relatively high PAH concentrations, and Turbinaria peltata (T. peltata; massive coral) showing the greatest PAH burdens among the investigated coral species. Biowater accumulation factors (BWAFs) varied substantially among reef organisms, and a significant positive relationship between log BWAFs and log KOW indicated that hydrophobicity was an important determinant of PAH accumulation. Apparent trophic magnification analysis revealed an overall tendency toward trophic dilution of PAHs across the coral reef ecosystem, indicating limited biomagnification potential under the investigated conditions. Comparative analysis of coral-associated microbial communities from 16S rRNA datasets revealed distinct microbial community composition and higher predicted PAH-related metabolic potential in T. peltata. The predicted enrichment of PAH-related metabolic pathways suggests that PAH transformation products may potentially enter microbial carbon metabolic pathways, where the transformed carbon could be utilized by microorganisms or contribute to carbon cycling within coral reef ecosystems, although direct functional validation is still required. Further studies integrating paired chemical and microbial measurements are required to determine whether these microbial processes contribute directly to PAH transformation and trophic transfer. Overall, this study provides new insights into PAH distribution and trophic behavior in coral reef ecosystems and offers an exploratory perspective on the potential role of coral-associated microbial communities in PAH fate under anthropogenic stress.