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

Abstract

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: 57·3μgSm−2h−1) in saltmarsh with considerable seasonal (max: 144·03μgSm−2h−1; min: 1·47μgSm−2h−1) and diurnal (max: 83·58μgSm−2h−1; min: 69·59μgSm−2h−1) changes in flux rates. Hydrogen sulfide was dominant (average: 21·2μgSm−2h−1, max: 79·2μgSm−2h−1; min: 5·29μgSm−2h−1) form in brackishmarsh and carbonyl sulfide (average: 1·09μgSm−2h−1; max: 3·42μgSm−2h−1; min: 0·32μgSm−2h−1) was dominant form in freshwater marsh. A greater amount of H2S was evolved from brackishmarsh (21·22μgSm−2h−1) as compared to the saltmarsh (2·46μgSm−2h−1) and freshwater marsh (0·30μgSm−2h−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 73·3μgSm−2h−1 for the saltmarsh, 32·1μgSm−2h−1 for brackishmarsh and 2·76μgSm−2h−1 for the freshwater marsh.