Influence of cadmium and zinc contamination on the sediment microbiome of estuarine and coastal ecosystems in the Southwest Coast of India.

Abstract

Metals and their nanoparticles can induce toxicities that influence the survival of both microorganisms and macroorganisms. The current study reports on the impact of heavy metal pollution on the microbiome of estuarine and coastal sediments, where the settling and final remineralization of organic matter occur. Sediment samples collected from the Cochin estuary along the southwest coast of India and its adjacent coast showed high concentrations of cadmium (Cd) and zinc (Zn). The contamination factor (CF), calculated by comparing the concentration of metals in each station with that of shale value for Cd and Zn, ranged from 5.2 to 8.7 and 1.5 to 2.0 respectively, in the estuarine and coastal stations. Microbiome analysis revealed that bacteria were common across all stations but varied in relative abundance. Proteobacteria, Chloroflexi, Actinobacteria, Desulfobacteria, and Acidobacteria were the major bacterial phylum found in all stations. More than 70% of the bacteria were tolerant to 1mM concentration of Cd. The findings of our study suggest that metal pollution can influence the microbiome of sediments in the estuaries and coasts. Bacteria with metal tolerance may dominate in polluted areas, but their participation in remineralization may be impaired, as evident in our previous reports. This impairment could ultimately influence the dynamics of the food web and the biogeochemical cycling of nutrients, necessitating further research.