Variation in PAH inputs and microbial community in surface sediments of Hamilton Harbour: Implications to remediation and monitoring

Variations in concentrations of polycyclic aromatic hydrocarbons (PAHs) and microbial community indicators were investigated in representative highly contaminated and less contaminated surface sediment sites of Hamilton Harbour. Inputs of PAH to the upper 3cm of sediments up to four times the average upper sediment concentrations were observed. Associated PAH fingerprint profiles indicated that the source was consistent with the PAH source to the industrial region of the harbour. Increased PAH loadings were associated with decreased bacterial populations as indicated by phospholipid fatty acid (PLFA) concentrations. However, relatively minor impacts on overall community composition were indicated. Porewater methane concentrations and isotopic data indicated a difference in the occurrence of methane oxidation between the two sites. This study confirms temporally limited transport of contaminants from highly impacted regions as a vector for contaminants within the harbour and the impact on microbial carbon cycling and bed stability.