Structural and functional responses of microbial communities in coastal sediments towards anthropogenic pollution caused by ship breaking activities.

Coastal ecosystems, like many others on the planet, face chronic threats from anthropogenic activities. The Alang-Sosiya Ship Breaking Yard (ASSBY) located near Bhavnagar in Gujarat, India, represents one such ecosystem impacted by decades of ship-breaking activities. This study aimed to assess the differences in microbial community composition between polluted coastal samples and pristine samples through high-throughput sequencing. Additionally, microbial co-occurrence networks and genes related to antibiotic and heavy metal resistance were predicted using metagenome mining. The analysis confirmed elevated heavy metal concentrations, particularly iron, in polluted samples. In non-polluted sites, alpha diversity indices showed a high microbial diversity compared to polluted sites. The bacterial communities from Deltaproteobacteria at non-polluted sites noticeably shifted to Gammaproteobacteria at polluted sites. Unclassified reads constituted a significant portion of the bacterial diversity. LEfSe (Linear discriminant analysis Effect Size) analysis identified potential bacterial biomarkers, including Pseudomonas, Halomonas and Rhodovulum, which were differentially abundant at polluted sites and may play roles in the biodegradation of xenobiotic compounds. Moreover, Co-occurrence network analysis validated these bacterial biomarkers from polluted sites and revealed their habitat-specific nature. Polluted metagenomes were enriched with genes related to aromatic compound degradation and stress responses, particularly genes for heavy metal and antibiotic resistance. These findings suggest that chronic pollution from ship-breaking activities has led to a shift in microbial communities, leading to an increased presence of resistance mechanisms in the polluted coastal environment to adapt to prolonged heavy pollution.