Spatial And Temporal Variations Of Denitrifier Communities In Freshwater Lakes

Lake microorganisms drive biogeochemical cycle in freshwater lake ecosystem.Denitrification is an important process for nitrogen removal in freshwater lake and it is crucial for controlling the eutrophication of lake ecosystem,because of the conversion of nitrate?NO₃^-?or nitrite?NO₂^-?to N₂O or N₂.Although researches on denitrifiers in aquatic systems,such as estuary and ocean,have rapidly advanced,the studies on freshwater lake denitrifiers communities are still limited.Based on denitrifiers'functional genes nirS and nosZ,this study applied quantitative PCR and high throughput sequencing technology to analyze the sediment and water denitrifiers community in Dianchi Lake and Erhai Lake on Yunnan Plateau and influential environmental factors.The main results obtained were as follows:?1?The vertical changes of denitrifier community abundance,richness,diversity and structure occurred in waters and sediments of either Dianchi Lake or Erhai Lake.Dianchi Lake waters had larger nirS and sediment nirS and nosZ abundance than Erhai Lake waters.Moreover,water column and sediment also differed sharply in denitrifier community structure.?2?The remarkable temporal changes of denitrifier community abundance,richness and diversity occurred in sediments of either Dianchi Lake or Erhai Lake,but the temporal and spatial variations of denitrifier community composition in these two lakes was not considerable.In addition,the Redundancy Analysis?RDA?showed that trophic status may play an important role in shaping sediment nirS-and nosZ-denitrifier communities in freshwater lakes.?3?The remarkable temporal and spatial variations of nirS-denitrifier community abundance,and nirS-and nosZ-denitrifier richness,diversity and structure occurred in bottom water of either Dianchi Lake or Erhai Lake.In addition,the results of RDA showed that trophic status may play an important role in shaping nirS-and nosZ-denitrifier communities in freshwater lakes bottom water.