Potential denitrification in wetland sediments with different plant species detritus

Abstract

The effect of detritus originating from different plant species on denitrifying capacity was investigated in a Swedish wastewater treatment wetland. Intact sediment cores containing sediment with a detritus layer were collected from wetland basins dominated by Typha latifolia, Phragmites australis, or Elodea canadensis in November 2000 and potential denitrification was measured using the acetylene-inhibition method. The cores from stands of E. canadensis showed more than three times higher denitrification capacity than the cores of the other plants. Bacterial abundance per unit dry weight was both highest and lowest in the detritus of P. australis, whereas the C/N ratio was lower in the cores of E. canadensis. This suggests that the submerged plant provided more organic material of high quality to support heterotrophic organisms. It is also possible that the surfaces of E. canadensis offered more or more suitable surfaces for bacterial growth and thereby increased the bacterial population. It is apparent that denitrifying bacteria were more favored by E. canadensis detritus than by detritus from the emergent plant species at the time of sampling. Since the turnover of plant detritus varies considerably among species, the seasonal variation in denitrification capacity is likely to be quite different for different plants.