BACKGROUND AND OBJECTIVES:
Coastal soil salinization is an environmental constraint that alters soil physicochemical conditions and may restructure microbial communities, while field patterns may also reflect land use and co-varying soil properties. The study objectives were to characterize soil physicochemical conditions together with bacterial diversity, composition, community dissimilarity, and predicted ecological functions at three tropical coastal sites in Palang, Tuban, East Java, with contrasting electrical conductivity.METHODS:
Electrical conductivity at sampling sites PA۸, PA۹, and PA۱۰ was ۱۳.۶۸, ۳.۷۴, and ۰.۵۰ decisiemens per meter, respectively. One composite soil sample per site was analyzed by nearly full-length bacterial small-subunit ribosomal ribonucleic acid gene amplicon sequencing. Amplicon sequence variants were inferred after denoising, and taxonomy was classified against a curated ribosomal reference database. Observed richness, Shannon and Gini-Simpson indices, Bray-Curtis and Weighted UniFrac principal coordinate analyses, taxonomic relative abundance, and taxonomy-based predicted functions were summarized descriptively. Exchangeable sodium, organic carbon, cation exchange capacity, phosphorus availability, texture, and culturable bacterial abundance were also compared among sites. Because site identity, electrical conductivity, land use, and other soil properties were confounded, no replicated salinity-effect inference was performed.FINDINGS: PA۸ had ۲,۰۵۲ observed sequence variants and a Shannon index of ۹.۶۱; PA۹ had ۵,۲۰۵ variants and a Shannon index of ۱۱.۳۹; and PA۱۰ had ۳,۱۴۵ variants and a Shannon index of ۱۱.۰۳. Taxonomic profiles differed among sites. PA۸ was characterized by Bacillota, Bacillales, and Incertae_Sedis_۱۴; PA۹ by Bacillota/Pseudomonadota, Bacillales, and Neobacillus; and PA۱۰ by Chloroflexota, Anaerolineales, and UTCFX۱. Weighted UniFrac distances were ۰.۳۲۶۶ for PA۹–PA۱۰, ۰.۴۸۵۰ for PA۸–PA۹, and ۰.۵۲۲۶ for PA۸–PA۱۰. Predicted chemoheterotrophy represented ۲۰.۴۶ percent, ۱۶.۹۷ percent, and ۲۳.۸۸ percent of post-filter reads at PA۸, PA۹, and PA۱۰, respectively. PA۸ also had the highest exchangeable sodium, whereas PA۱۰ had the highest organic carbon, cation exchange capacity, Olsen-available phosphorus, and culturable bacterial abundance.CONCLUSION: The three sites showed distinct physicochemical and bacterial community profiles, but the observational design does not permit causal attribution to salinity or generalization to salinity classes. The findings provide a site-specific environmental baseline and hypotheses for future replicated studies.