鲴鲢鳙混养系统中微生物对氮素迁移转化的影响

The effects of microorganisms on the migration and transformation of nitrogen in the polyculture system of Plagiogathops microlepis Bleeker,Hypophthalmichthys molitrix and Aristichthys nobilis

通过实验室模拟富营养化水体进行鲢(Hypophthalmichthys molitrix)鳙(Aristichthys nobilis)鲴(Plagiogathops micrloepis Bleeker)混养,结合同位素标记与微生物检测,研究其中沉积物微生物群落的变化及其对氮素迁移转化的影响,揭示鲢鳙鲴混养作用机制.结果表明,鲢鳙鲴混养增加了沉积物中氨化细菌(芽孢杆菌属与假单胞菌属)的数量,实验结束时,与其它组相比,鲢鳙鲴组的芽孢杆菌属(Bacillus)与假单胞菌属(Pseudomonas)总占比最高,为31.2%,这增强了氨化作用,减少了沉积物中有机氮的含量,使得鲢鳙鲴组的δ^(15)N(底质沉积物)在实验结束时降至726.8‰.鲢鳙鲴混养提高了沉积物中反硝化菌属(动胶菌属与芽胞杆菌属)的数量,实验结束,鲢鳙鲴组动胶菌属(Zoogloea)与芽胞杆菌属(Bacillus)占比显著高于鲢鳙组(P<0.05),达到8.17%、33.7%,使得系统中反硝化反应加强,使水体中更多的硝酸盐氮转化为气态氮并移出水体,实验结束时,与其它组相比,鲢鳙鲴组δ^(15)N_(硝酸盐氮)降低至96.3‰,^(15)N总含量也降低至6.94μmol.

The polyculture system of Plagiogathops microlepis Bleeker(Xenocypris microlepis),Hypophthalmichthys molitrix(Silver carp)and Aristichthys nobilis(bighead carp)was set up in simulated eutrophic water.The dynamics of microbial communities and their effects on the migration and transformation of nitrogen in the sediments were investigated by applying isotopic labeling and microbial analysis to reveal the underlying mechanism of the polyculture system.The results showed that:The polyculture of Xenocypris microlepis,silver carp and bighead carp could increase the proportion of Pseudomonas and Bacillus involved in the ammonification process in the sediments.Comparing with the silver carp and bighead carp group,the total proportion of Bacillus and Pseudomonas in the polyculture group was the highest(31.2%)at the end of experiment,showing that it enhanced ammonification process and thus,reduced the content of organic nitrogen in the sediments.Consequently,theδ^(15)N(substrate sediment)of the polyculture group decreased to 726.8‰.The polyculture of Xenocypris microlepis,silver carp and bighead carp could increase the proportion of denitrifying bacteria(Zoogloea and Bacillus)in the sediments.The proportion of Zoogloea and Bacillus in the polyculture group was significantly higher than that in the silver carp and bighead carp group(P<0.05),reaching 8.17%and 33.7%,respectively.Therefore,the denitrification process was enhanced in the system,converting more nitrate into nitrogen gas in the water and finally releasing this gas from this water.At the end of the experiment,in the polyculture group,theδ^(15)N(nitrate nitrogen)decreased to 96.3‰and the total content of 15N decreased to 6.94μmol.