Abstract

• In this study, vertical soil cores were collected from two habitats (mudflat and salt marshes) in Zeekone, Tawpun, Kalwi, and Karaikdo. The aim was to examine the organic carbon content and physicochemical properties of the soil's vertical profile (within 0-60 cm). Eight salt marsh species were identified based on their vegetation cover, including Sesuvium portulacastrum, Phragmites australis, Distichlis spicata, Puccinellia species, Paspalum species, Spartina maritima, Typha angustifolia, and Schoenoplectus americanus.The results showed that soil organic carbon (SOC) content decreased with depth in the Zeekone, Tawpun, and Karaikdo stations. In contrast, an increasing trend was observed in the Kalwi station. For soil physical properties, dry bulk density (gcm⁻³) increased with depth at Zeekone, Tawpun, and Karaikdo, but not at Kalwi. The mudflat in the Kalwi station had the highest soil salinity value (5.98 ± 0.67), while the Phragmites australis salt marsh at the Zeekone station had the lowest (0.06 ± 0.01). Soil pH values across all stations ranged from weakly acidic to weakly alkaline.The highest SOC content was found in the Sesuvium portulacastrum salt marsh at Zeekone and the mudflat at Tawpun, with mean values of 1.00 ± 0.57% and 1.16 ± 0.71%, respectively. The sediment types in the Zeekone and Tawpun stations were sandy loam and sand. Kalwi station consisted of loamy sand and sand, and Karaikdo station had loam and sandy loam sediment types.