A field study was conducted at Schleswig-Holstein in Germany to evaluate the possible factors controlling carbon and sulfate dynamics along a toposequence ! of daily to seasonally flooded coastal salt marsh soils. The soil at the top end of the salt marsh (with a height of 1.8 m above sea level: a.s.l. and a dense vegetation cover) was salic silty to clayic Typic Sulfaquent (Salzrohmarsh), while the soil at the bottom end (with some salt bushes and a 1.4 m a.s.l.) was sandy to silty Haplic Sulfaquent (Übergangsmischwatt). The mean (depth: 0-100 cm) values of pH were around 7, and of redox potentials (Eh) in the Typic Sulfaquent were ranged from -162 to +104 mV during all the seasons. The average net-emission of CO₂ above the vegetation cover was negative (-14.0 g m^-2 yr^-1) for the Haplic Sulfaquent but highly positive (857 g m^-2 yr^-1) for Typic Sulfaquent throughout the year. The annual average emissions of CH₄ were almost 10 fold higher in Haplic Sulfaquent (0.3 g m^-2 yr^-1) than that of the Typic Sulfaquent (0.03 g m^-2 yr^-1). The average maximum concentrations of CO₂ were detected within the surface soils at the depth of 20 to 40 cm in both the profiles. The surface soils at depth of 0 to 20 cm, where the concentrations of CO₂ were measured relatively low though the values were about 5 to 20 times higher than that of the atmospheric (350 ppmv) concentration. The concentrations of CH₄ at different seasons showed almost inverse relationships with the concentrations of CO₂. In all the profiles, the concentrations of CH₄ were very low and varied significantly (p≤0.05) with the seasons and depth function. The concentrations of CH₄ showed no dependence to temperature. The SO₄ contents were observed maximum in the Typic Sulfaquent followed by Haplic Sulfaquent during all the seasons. There was no noticeable correlation (r = -0.09) between SO₄ and CH₄ concentrations. Moreover, even CH₄ was determined at depths where the SO₄ concentration in the soil solution was around 1200 mg SO₄ L^-1.