Due to anthropogenic activities, coastal sediments are prone to hydrocarbon contamination, which can be reflected in the microbial community structure, diversity, and metabolism. To evaluate these impacts, the chemical contamination factor (CF 16PAHs ) and the Quality Ratio (QR) index for ecological risk assessment were integrated with bacterial community characterization (16S rRNA gene sequencing) in Sepetiba Bay (Brazil), a system highly impacted by human activities. CF 16PAHs presents a decreasing trend from the internal to the external sector, while QR ranked most internal stations as moderate to high ecological risk. Canonical correspondence analysis accounted for 22.42% of the total variance in bacterial community composition, suggesting that CF 16PAHs played a significant role in structuring the assemblages. Proteobacteria predominated (53.4%), especially Gamma- and Deltaproteobacteria (29%, 21%, and 3% respectively) and the most prevalent genera were Vibrio (12%), Desulfatiglans (11%), and Bacillus (8%). Cluster correlation analysis showed that nearly half of all ASVs were significantly associated with PAH levels. Linear discriminant analysis identified habitat-specific bioindicators across the contamination gradient, including Woeseiaceae (low risk), Bacillus (moderate risk), Desulfobulbus and Desulfatiglans (high risk). Overall, the bacterial community structure was consistent with the QR risk classification, suggesting the efficiency of combining molecular and geochemical approaches to assess sediment quality and contamination risk in coastal ecosystems. • Integrated PAH, enzymatic, and 16S data to assess sediment contamination. • Bacterial bioindicators emerged along the PAH contamination gradient. • Bacterial community patterns served as indicators of sediment quality. • Quality Ratio Index applied to evaluate PAH-driven ecological risk.
Carvalho et al. (Fri,) studied this question.