DEEP DAVE, AMITA MISHRA, S.K. PATEL AND PRITI MAHLA
Abstract
Coastal sludge environments function as dynamic interfaces where factors, such as salinity, redox conditions, and human activities, shape microbial diversity. This study conducted a comparative examination of the microbiomes in seawater (S1), sediment (S2), and hypersaline saltpan (S3) sludge from Mundra Port, Gujarat, using 16S rRNA (V3âV4) Illumina MiSeq sequencing. The study revealed distinct microbial community structures across these habitats: seawater was primarily dominated by Proteobacteria, Bacteroidota, and Cyanobacteria; sediments showed enrichment of Desulfobacterota, Firmicutes, and Chloroflexi; whereas saltpans were characterized by halophilic archaea, notably Halobacteriota. Analyses of alpha and beta diversity confirmed that sediments exhibited the highest richness and demonstrated a pronounced habitat-specific separation, largely influenced by salinity. Functional predictions using PICRUSt2 indicated aerobic carbon and nitrogen cycling in seawater, anaerobic sulfur metabolism and hydrocarbon degradation in sediments, and osmoregulatory and stress-response pathways in saltpans. Collectively, the findings illustrate a distinct ecological gradient from marine to hypersaline environments, highlighting reduced diversity but enhanced functional specialization under extreme salinity conditions. These results emphasize the biogeochemical importance of port-associated sludge systems and their potential as reservoirs of halophilic and anaerobic microorganisms with applications in biotechnology.