太湖人工生态系统中氮循环细菌分布

对太湖五里湖的以水生高等植物为主的湖泊人工生态系统，用最大可能数（ＭＰＮ）法，测定了该系统内各种生态类型水生高等植物群落内的４类氮循环细菌的分布．结果表明，反硝化细菌的最大可能数（ＭＰＮ），在水生高等植物群落内水体中较敞水区湖水高２－５个数量级，差异极显著（Ｐ＜０．０１），漂浮植物群落内水体的反硝化细菌ＭＰＮ值较沉水和浮叶植物群落内水体高２－３个数量级，差异极显著（Ｐ＜０．０１）；硝化细菌ＭＰＮ值，敞水区湖水高于凤眼莲、水花生群落内水体，差异显著（ Ｐ＜ ０． ０５），菱群落与其他群落比较，亦有极显著性差异（ Ｐ＜ ０． ０１）；亚硝化细菌ＭＰＮ值，在水生高等植物群落内的水体中较敞水区高 ３－ ４个数量级，差异极显著（ Ｐ＜ ０． ０１） ；氨化细菌ＭＰＮ值，在水生高等植物群落内的水体中高于敞水区水体．除硝化细菌外，反硝化、亚硝化及氨化细菌均在根际处最为密集，且由根际向外呈现递减趋势．

Distribution of Nitrogen Cycle Bacteria in an Artificial Ecosystem of Taihu Lake

This paper first report the distribution and role of four nitrogen cycle bacteria in the artificial ecosystem of Taihu Lake. These nitrogen cycle bacteria include ammonifying bacteria, denitrifying bacteria, nitrobacteria and nitroasobacteria, determined with MPN method. The MPN values of denitrifying bacteria in the water covered by Alternanthera philoxeroides and Eichhornia crasipes are about 2 - 3 and 2 - 5 order-of-magnitudes higher than the water vegetated with other macrophytes and unvegetated water respectively. There is significant difference between them (P < 0. 01). The MPN values of ammonifying bacteria in vegetated water are markedly higher than that in unvegetated water. The MPN values of nitrosobacteria in vegetated water are notably higher than those in unvegetated water (P < 0. 01 ). The MPN values of nibobacteria and nitrosobacteria in the water vegetated with submerged plant are higher than those in the water covered by floating plant. The MPN values of ammonifying and denitrifying bacateria, nitrosobacteria are very dense in rhizosphere, and decrease from rhizosphere to outside.