Soil salinity restructures microbial communities in coastal croplands of Kuakata, Bangladesh

Soil salinity is an increasing threat to agriculture in coastal regions, where climate change and sea-level rise intensify salt intrusion. Coastal agriculture in Bangladesh faces increasing salinity stress, yet its effects on soil microbial assembly and nutrient cycling remain poorly understood. This study examined how salinity affects soil microbial communities in agricultural soils from Kuakata, Bangladesh, using near-full-length 16 S rRNA amplicon sequencing. Soil samples were collected from 10 saline and 6 non-saline croplands, with saline fields showing visible signs of crop stress. Saline soils had substantially higher electrical conductivity (4.82 vs. 0.5 dS/m), exchangeable sodium percentage (33.78% vs. 11.37%), sodium adsorption ratio (2.38 vs. 0.41), pH (6.83 vs. 5.40), and sulfur content (288.9 vs. 120.62 mg/kg) than non-saline soils. Microbial communities differed significantly between soil groups and saline soils showed reduced microbial evenness. Although Proteobacteria and Chloroflexi dominated both soil types, saline soils were enriched in anaerobic and sulfur-associated-taxa, including Desulfobacterota, Deferrisomatota, Pseudomonas, and Thioalkalispira-Sulfurivermis, whereas non-saline soils showed higher abundance of taxa linked to more diverse soil ecological functions. Predicted phenotype analysis indicated a higher relative abundance of anaerobic-associated microorganisms in saline soils (36.4%) than in non-saline soils (29.3%). Together, these findings indicate that salinity strongly restructures soil microbial communities and may contribute to reduced soil health and agricultural productivity in coastal farming systems.