Sulfate reducer and sulfur oxidizer respond differentially to the invasion of Spartina alterniflora in estuarine salt marsh of China

Abstract

Although salt marshes are productive ecosystems hosting an active sulfur cycle, little is known regarding the response of functional bacteria involved in the sulfur redox cycling to invasive Spartina alterniflora. We compared community abundance and composition of sulfate reducing bacteria (SRB) and sulfide oxidizing bacteria (SOB) in sediments vegetated by the invasive plant S. alterniflora and native plants (Phragmites australis; Scirpus mariqueter) in salt marsh of the Yangtze Estuary, China. The community structures were assessed using clone libraries, sequencing and quantitative PCR, based on functional markers of sulphite reductase (Dsr) (dsrB) and sulfate thiohydrolase (the Sox pathway) (soxB) genes. Copy numbers of dsrB gene in soils vegetated by S. alterniflora were significantly higher than those in soils by native plants, while there were no significant difference of the abundance of soxB genes between S. alterniflora and native plants. With respect to sulfate reducing bacteria, Desulfobacterales dominated in soils of all vegetations (52.2%–72.3%), and families Desulfovibrionales and Clostridiales were observed at high tidal elevation, while Syntrophobacterales and Desulfarculales were only present at low tidal elevation. While in the sulfide oxidizing bacteria community, the phylum Chlorobia was only detected and even dominated at low tidal zone. Canonical correspondence analysis (CCA) suggested that ferric iron was the major factor controlling the community structure of both sulfate reducing bacteria and sulfide oxidizing bacteria across various vegetations. Sulfate was closely correlated with sulfate reducing bacteria and sulfide oxidizing bacteria communities from S. alterniflora at both high and low tidal zones. Our results indicated the invasion of S. alterniflora into coastal salt marsh of China would change the microbial composition of SRB and SOB, and promote the proliferation of sulfate reducing bacteria to accelerating the sulfur cycling, and which in turn favor the invasion of sulfur tolerant plant in coastal wetlands.