Bacterial communities reflect the spatial variation in pollutant levels in Brazilian mangrove sediment

The majority of oil from oceanic oil spills converges on coastal ecosystems such as mangrove forests. A major challenge to mangrove bioremediation is defining the mangrove's pollution levels and measuring its recuperation from pollution. Bioindicators can provide a welcome tool for defining such recovery. To determine if the microbial profiles reflected variation in the pollutants, samples from different locations within a single mangrove with a history of exposure to oil were chemically characterised, and the microbial populations were evaluated by a comprehensive range of conventional and molecular methods. Multivariate ordination of denaturing gradient gel electrophoresis (DGGE) microbial community fingerprints revealed a pronounced separation between the sediment and rhizosphere samples for all analysed bacterial communities (Bacteria, Betaproteobacteria, Alphaproteobacteria, Actinobacteria and Pseudomonas). A Mantel test revealed significant relationships between the sediment chemical fertility and oil-derived pollutants, most of the bacterial community fingerprints from sediment samples, and the counts by different cultivation strategies. The level of total petroleum hydrocarbons was significantly associated with the Bacteria and Betaproteobacteria fingerprints, whereas anthracene and the total level of polycyclic aromatic hydrocarbons were associated with the Actinobacteria. These results show that microbial communities from the studied mangrove reflect the spatial variation of the chemicals in the sediment, demonstrating the specific influences of oil-derived pollutants.