Effects of the Rhizospheres of Three Submerged Plants on the Abundances of Functional Genes of Typical Nitrogen Cycle Microorganisms in Sediments

Purpose Nitrification-denitrification and anaerobic ammonium oxidation are important denitrification ways in a lake ecosystem. The abundance and community structure of nitrogen circulating microorganisms can reflect the ecological environment of the lake, and it is an important indicator to judge the ecological restoration.

Method Simulation experiment and field investigation were designed to study the effects of Egeria densa, Myriophyllum verticillatum and Vallisneria natans rhizosphere on the inorganic nitrogen content and the functional gene abundance of several typical nitrogen cycle microorganisms using qPCR method, such as ammonia oxidizing archaea (AOA), aerobic ammonia-oxidizing bacteria (AOB), denitrifying bacteria and anaerobic ammonium oxidation (Anammox).

Result Three submerged plants could remarkably reduce the ammonia nitrogen in the rhizosphere sediment (P<0.05). The copies ofnirS, nirK and nosZ gene were increased in M. verticillatum and V. natans rhizosphere sediments. The copies of AOA amoA were increased but AOB amoA were decreased in M. verticillatum and V. natans rhizosphere sediments. nirS, nirK and nosZ gene copies were decreased, but hzO gene copies were increased significantly in E. densa rhizosphere sediments (P<0.05).

Conclusion Denitrification was the main way of nitrogen removal in M. verticillatum and V. natans rhizosphere sediments. M. verticillatum and V. natans were selective for AOA amoA, and AOA was the main contributor to the ammoxidation process in sediments. Anaerobic ammonium oxidation process was the main denitrification way of E. densa rhizosphere sediments.