The Influence of Vegetation on Microbial Enzyme Activity and Bacterial Community Structure in Freshwater Constructed Wetland Sediments

Microorganisms play important roles in wetland ecosystems, but little is known about the influence of wetland plants on microbial community structure and activity. A greenhouse experiment was conducted to study the short-term influence of wetland vegetation on the sediment microbial community. Mesocosms were either planted with Juncus effusus, Carex lurida, or Dichanthelium acuminatum var. acuminatum or remained unvegetated. After eight weeks, sediment samples were taken and assayed for the activity of five microbial extracellular enzymes associated with carbon, nitrogen, and phosphorus cycling. beta-1,4-glucosidase, phosphatase, and N-acetylglucosaminidase exhibited similar activity for all vegetation treatments, while the activity of the phenolic-degrading enzymes phenol oxidase and peroxidase was higher in sediments with no vegetation. Denaturing gradient gel electrophoresis and sequencing of partial 16S rRNA genes indicate differences in the sediment bacterial community associated with each plant regime. Acidobacteria, Firmicutes and Proteobacteria were the dominant phyla, although unvegetated sediments contained proportionally fewer Firmicutes and Alphaproteobacteria. This study provides insights into the structure of wetland bacterial communities and suggests that vegetation can influence both bacterial community structure and specific enzyme activity in wetland sediments. Moreover, these influences can occur over a relatively short time and could occur within just a few months of vegetation changes.