为评估水产养殖中小球藻在调控水体氨氮(NH₄⁺-N)和亚硝酸盐氮(NO₂^--N)的应用前景，实验以普通小球藻为对象，饲料废水为培养液，首先检测了曝气、光照、光照+曝气条件下普通小球藻细胞密度及水体中NH₄⁺-N和NO₂^--N的时间变化规律，其次分析了时间(X₁)、光照强度(X₂)或初始藻密度(X₃)对2种氮盐去除率(Y)的影响，最后评估了普通小球藻去除水体中NH₄⁺-N、NO₂^--N和NO₃^--N的效果，并解析了普通小球藻同化水体NO₂^--N的潜在途径。结果显示，普通小球藻在适宜的光照条件下具有极佳的氮盐去除能力，其在18 000 lx时对NH₄⁺-N去除率高达96.23%，在9 000 lx时对NO₂^--N去除率高达99.19%；初始藻密度在2.5×10⁵ 个/mL时对NH₄⁺-N、NO₂^--N去除率最高，分别为94.92%和99.05%。氮盐去除率与处理时间和光照强度的回归方程：Y_NH4^＋-N=1.189X₁+5.79×10^-4X₂+24.158(R²=0.664)，Y_NO2^--N=1.562X₁+1.909×10^-3X₂-26.078(R²=0.762)；氮盐去除率与处理时间和初始藻密度的回归方程为：Y_NH4^＋-N=0.888X₁+1.02×10^-5X₃+32.555(R²=0.408)，Y_NO2^--N =1.746X₁+1.64×10^-5X₃-17.250(R²=0.613)。普通小球藻去除氮盐顺序为NH₄⁺-N＞NO₃^--N＞NO₂^--N；NH₄⁺-N同化阶段普通小球藻亚硝酸盐还原酶活性显著低于NO₂^--N同化阶段。研究表明，普通小球藻能显著降低水体NH₄⁺-N与NO₂^--N含量，NO₂^--N可能是由藻细胞内亚硝酸盐还原酶还原成NH₄⁺-N而被普通小球藻同化吸收。该研究结果可为养殖水体原位生物修复提供科学依据。

Since the non-ionic ammonia and ionic ammonia can be converted into each other, in aquaculture, ammonia nitrogen (NH₄⁺-N) and nitrite nitrogen (NO₂^--N) are the key factors that affect the growth and development of aquatic animals. Therefore, the removal of NH₄⁺-N and NO₂^--N in aquaculture water is of great significance to ensure the health of aquaculture animals. As we all know, microorganisms and algae play important roles in maintaining the ecological balance of aquaculture ponds. It has been proved that Chlorella had the ability of purifying aquaculture water, with different Chlorella species different removal efficiency on NH₄⁺-N and NO₂^--N. Chlorella vulgaris is widely used in aquaculture, however, we know little about the removal effect on nitrogen nutrient especially NO₂^--N by C. vulgaris. Given the shortage of effective ecological control measures in aquaculture, it is of great significance to illustrate the removal effect of NH₄⁺- N and NO₂^--N by C. vulgaris and related influencing factors. Aiming to evaluate the application prospect of C. vulgaris in purifying NH₄⁺-N and NO₂^--N in water, in the present study, C. vulgaris was taken as the research object and feed wastewater was taken as the culture medium. We firstly detected the cell density of C. vulgaris and the temporal variations of NH₄⁺-N and NO₂^--N in water under aeration, light, combined light and aeration conditions. Then we analyzed the effects of time (X₁), light intensity (X₂) or initial C. vulgaris density (X₃) on the removal rates of NH₄⁺-N and NO₂^--N (Y). Finally, we evaluated the removal efficiency of NH₄⁺-N, NO₂^--N and NO₃^--N from water by C. vulgaris, and we analyzed the potential pathway of NO₂^--N assimilation by C. vulgaris. The results showed that C. vulgaris could remove NH₄⁺-N, NO₂^--N and NO₃^--N significantly under suitable light conditions. The NH₄⁺- N removal rate reached up to at 18 000 lx (96.23%), and NO₂^--N removal rate reached up to 99.19% at 9 000 lx. The initial density of C. vulgaris at 2.5×10⁵ cells/mL had the highest removal rates for NH₄⁺-N and NO₂^--N, accounting 94.92% and 99.05%, respectively. The regression equation of NH₄⁺-N and NO₂^--N removal rates with treatment time and light intensity was as follows: Y_NH4⁺-N=1.189X₁+5.79×10^-4X₂+24.158 (R²=0.664), Y_NO2^--N=1.562X₁+1.909×10^-3X₂-26.078 (R²=0.762). The regression equation of NH₄⁺-N and NO₂^--N removal rates with treatment time and initial C. vulgaris density was as follows: Y_NH4⁺-N =0.888X₁+1.02×10^-5X₃+32.555 (R²=0.408), Y_NO2^--N =1.746X₁+1.64×10^-5X₃-17.250 (R²=0.613). The order of nitrogen removal by C. vulgaris was NH₄⁺-N>NO₃^--N>NO₂^--N, and the activity of nitrite reductase in C. vulgaris at NH₄⁺-N decline stage was significantly lower than that at NO₂^--N decline stage. In conclusion, C. vulgaris can significantly reduce the contents of NH₄⁺-N and NO₂^--N in water, and NO₂^--N may be reduced to NH₄⁺-N by intracellular nitrite reductase and assimilated by C. vulgaris. These results provide scientific basis for in-situ bioremediation of aquaculture waters.

S 949

国家重点研发计划 (2019YFD0900301)；中国水产科学研究院基本科研业务费(2021XT0701)