Microbial indicators along a metallic contamination gradient in tropical coastal sediments

The structure and diversity of microbial community inhabiting coastal sediments reflect the exposition to con-taminants. Aiming to assess the changes in the microbiota from Sepetiba Bay (SB, Brazil) sediments, correlations between the 16S rRNA gene data (V4-V5 region), metal contamination factors (CF), and the ecological risk classification provided by the Quality Ratio (QR) index were considered. The results show that microbial di-versity differs significantly between the less (SB external sector) and the most (SB internal sector) polluted sectors. Also, differences in the microbial community structure regarding the ecological risk classifications validated the QR index as a reliable tool to report the SB chronic contamination. Microbial indicator genera resistant to metals (Desulfatiglans, SEEP-SRB1, Spirochaeta 2, among others) presented mainly anaerobic me-tabolisms. These genera are related to the sulfate reducing and methanogenic metabolisms probably partici-pating in the natural attenuation processes but also associated with greenhouse gas emissions. In contrast, microbial indicator genera sensitive to metals (Rubripirellula, Blastopirellula, Aquibacter, among others) presented mainly aerobic metabolisms. It is suggested that future works should investigate the metabolic functions to evaluate the influence of metallic contaminants on microbial community inhabiting SB sediment.

Automated summary

This study assessed the changes in microbial communities in sediments from Sepetiba Bay in Brazil. The results showed significant differences in microbial diversity between less polluted and highly polluted sectors. The study also validated the use of the Quality Ratio index as a reliable tool for assessing chronic contamination in the bay.