Effects of potassium monopersulfate on nitrification activity and bacterial community structure of sponge biocarrier biofilm in <i>Litopenaeus vannamei</i> aquaculture system

Effects of potassium monopersulfate (KMPS) on the nitrification activity, aquacultural water quality and bacterial community structure of sponge biocarriers with pre-cultured biofilm (SBBF) were analysed through shaking flask experiments and L. vannamei aquaculture experiments. Changes in the ammonia oxidation rate (AOR) and nitrite oxidation rate (NOR) of SBBF under six KMPS concentration treatments (0, 1, 2, 3, 4 and 5 mg/L) were studied. The results showed that the AOR and NOR of SBBF treated with high concentrations of KMPS (3, 4 and 5 mg/L) were significantly lower than those of the control group (CK) (p < 0.05). However, compared with the first dosing of NH4Cl and NaNO2, the inhibition of AOR and NOR by KMPS on AOR and NOR was weakened after the second and third dosing times. That is, AOR and NOR can recover partially or completely over time. The L. vannamei aquaculture experiment was performed using four concentrations of KMPS (0, 2, 4 and 8 mg/L). The results showed that with increasing KMPS dosage, the average and peak concentrations of NH4+-N and NO2–-N in each treatment significantly increased (P < 0.05), and the final body weight of shrimp significantly decreased (P < 0.05). Furthermore the highest dose (8.0 mg/L) of KMPS reduced the survival rate by 9.33% compared to the CK. High-throughput sequencing analysis of the biofilm structure showed that the relative abundances of Nitrospirota, Nitrosomonas and Nitrococcus, which are related to nitrogen cycling, and beneficial bacteria including Firmicutes and Bacilli decreased with the addition of KMPS (p < 0.05).本研究通过摇瓶实验与凡纳滨对虾（Litopenaeus vannamei）养殖实验，探究过一硫酸氢钾（potassium monopersulfate, KMPS）对预培养生物膜海绵生物载体（sponge biocarriers with pre-cultured biofilm, SBBF）的硝化活性、养殖水质及细菌群落结构的影响。设置6组KMPS浓度梯度处理（0、1、2、3、4、5 mg/L），分析SBBF的氨氧化速率（ammonia oxidation rate, AOR）与亚硝酸盐氧化速率（nitrite oxidation rate, NOR）的变化特征。结果显示，高浓度KMPS（3、4、5 mg/L）处理组的SBBF的AOR与NOR均显著低于对照组（CK）（p<0.05）。与首次投加氯化铵（NH4Cl）与亚硝酸钠（NaNO2）时相比，第二次、第三次投加后KMPS对AOR与NOR的抑制作用有所减弱，即AOR与NOR可随培养时间推移实现部分或完全恢复。本研究另设置4组KMPS浓度（0、2、4、8 mg/L）开展凡纳滨对虾养殖实验，结果表明：随着KMPS投加浓度升高，各处理组水体中氨氮（NH4+-N）与亚硝态氮（NO2–-N）的平均浓度及峰值浓度均显著升高（P<0.05），对虾最终体重显著降低（P<0.05）；且最高投加浓度（8.0 mg/L）组对虾存活率较对照组降低9.33%。对生物膜群落结构的高通量测序分析显示，与氮循环相关的硝化螺旋菌门（Nitrospirota）、亚硝化单胞菌属（Nitrosomonas）、硝化球菌属（Nitrococcus），以及厚壁菌门（Firmicutes）、芽孢杆菌纲（Bacilli）等有益菌的相对丰度，均随KMPS的添加显著下降（p<0.05）。