Flux of Reduced Sulfur Gases Along a Salinity Gradient in Louisiana Coastal Marshes

Seasonal and diurnal reduced sulfur gas emissions were measured along a salinity gradient in Louisiana Gulf Coast salt, brackish and freshwater marshes. Reduced sulfur gas emission was strongly associated with habitat and salinity gradient. The dominant emission component was dimethyl sulfide (average: 57·3 g S m 2 h 1) in saltmarsh with considerable seasonal (max: 144·03 g S m 2 h 1; min: 1·47 g S m 2 h 1) and diurnal (max: 83·58 g S m 2 h 1; min: 69·59 g S m 2 h 1) changes in flux rates. Hydrogen sulfide was dominant (average: 21·2 g S m 2 h 1, max: 79·2 g S m 2 h 1; min: 5·29 g S m 2 h 1) form in brackishmarsh and carbonyl sulfide (average: 1·09 g S m 2 h 1; max: 3·42 g S m 2 h 1; min: 0·32 g S m 2 h 1) was dominant form in freshwater marsh. A greater amount of H2S was evolved from brackishmarsh (21·22 g S m 2 h 1) as compared to the saltmarsh (2·46 g S m 2 h 1) and freshwater marsh (0·30 g S m 2 h 1). Emission of total reduced sulfur gases decreased with decrease in salinity and distance inland from the coast. Emission of total reduced sulfur gases over the study averaged 73·3 g S m 2 h 1 for the saltmarsh, 32·1 g S m 2 h 1 for brackishmarsh and 2·76 g S m 2 h 1 for the freshwater marsh.