鲢鱅鲴混养对水环境及氮素迁移转化的影响

利用¹⁵N稳定同位素技术研究混养细鳞斜颌鲴对鲢鱅鱼水环境及氮素迁移转化的影响.结果显示：实验期间，鲴鲢鱅组各营养盐浓度经过短暂升高后迅速降低，实验结束时，TN，TP，NO₃^--N，NO₂^--N，PO₄^3--P浓度分别达到2.67，0.13，0.93，0.026，0.0035mg/L，鲢鱅组各营养盐浓度总体保持增长趋势并于第10d后显著大于鲴鲢鱅组相应值（P<0.05），到实验结束分别为鲴鲢鱅组的1.80，1.69，1.73，1.72，1.83倍.与对照组相比，有鱼组的叶绿素浓度Chla和藻细胞密度明显下降，到实验结束，鲢鱅组的Chla和藻细胞密度分别为34.69mg/m³，1.96×10⁶cells/L，鲴鲢鱅组分别为25.32mg/m³，1.9×10⁶cells/L，均显著低于对照组（P<0.05）.同位素分析结果显示：标记物¹⁵N微囊藻进入系统后，部分被鲢鱅鱼摄食同化为机体组成部分，再通过鱼类分泌，排泄等方式进入水体，水体中含氮营养盐被藻类生长吸收，此外，一部分微囊藻沉淀和鱼类排泄物作为沉积腐质被鲴鱼摄食同化为其机体组成部分.

Effects of Plagiogathops micrloepis Bleeker,Hypophthalmichthys molitrix and Aristichthys nobilis polyculture on water environment and nitrogen migration and transformation

¹⁵N stable isotope tracer technique was employed to study the effects of Plagiogathops micrloepis Bleeker (Xenocypris microlepis), Hypophthalmichthys molitrix (Silver carp) and Aristichthys nobilis (bighead carp) polyculture on water environment and nitrogen migration and transformation. The results showed that each nutrient salt concentration in the Xenocypris microlepis, silver carp and bighead carp group decreased rapidly after a brief increase and at the end of the test, while TN, TP, NO₃^--N,NO₂^--N and PO₄^3--P respectively reached 2.67, 0.13, 0.93, 0.026 and 0.0035mg/L. The nutrient concentration of the silver carp and bighead carp group generally maintained an increasing trend and was significantly greater than the corresponding value of the Xenocypris microlepis, silver carp and bighead carp group after the 10th day (P<0.05), while TN, TP, NO₃^--N, NO₂^--N and PO₄^3--P of it were 1.80, 1.69, 1.73, 1.72 and 1.83 times of that group when the experiment was over. Chl a and the cell density of algae in the fish group decreased significantly compared with the control group, while the silver carp and bighead carp group reaching 34.69mg/m³, 1.96×10⁶cells/L and the Xenocypris microlepis, silver and bighead carp group reaching 25.32mg/m³, 1.9×10⁶ cells/L respectively at the end of the test, which were significantly lower than the control group (P<0.05). The isotope analysis showed that Microcystis marked ¹⁵N was assimilated partly by the silver carp and bighead carp body and entered the water body through fish secretion and excretion, then the nitrogen in water were absorbed by algae after being put into the water. In addition, some Microcystis sedimentation and fish excrement were assimilated as the sedimentary humus into the body of Xenocypris microlepis by ingestion.