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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). [ABSTRACT FROM AUTHOR]

Chlorella pyrenoidosa is a widely used microalgae in the aquaculture process of Litopenaeus vannamei. In order to evaluate the effects of supplementing C. pyrenoidosa on water quality, shrimp growth performance, and biofilm bacterial community structure in L. vannamei aquaculture systems, C. pyrenoidosa suspension was supplemented in the precultured biofilm (PB) and water exchange (WE) culture systems. The results showed that supplementation with C. pyrenoidosa significantly increased the turbidity and the concentrations of total ammonia nitrogen (TAN) and nitrite nitrogen (NO 2 − ─N) in the PBC system (the PB system supplemented with C. pyrenoidosa), but had no significant effect on those in the WEC system (the WE system supplemented with C. pyrenoidosa). However, the TAN concentration of all systems remained at a low level (<0.1 mg/L) throughout the experiment. Additionally, supplementation with C. pyrenoidosa decreased the final concentrations of total phosphorus in the PBC and WEC systems by 15.74% and 23.33%, respectively. With the supplementation of C. pyrenoidosa, the final weight, final biomass, and average daily growth rate of L. vannamei increased, while the feed conversion ratio decreased. 16srRNA high-throughput sequencing results showed that the supplementation of C. pyrenoidosa to the PBC system resulted in a decrease in the relative abundances of Proteobacteria and Bacteroidetes and an increase in the relative abundance of Acidobacteria. Compared to those in the initial biofilm sample, the relative abundances of nitrifying bacteria, Nitrosococcus, Nitrosomonas, Nitrococcus, and Nitrospira, in PBCF (biofilm in the PB systems with C. pyrenoidosa) and PBOF (biofilm in the PB systems without C. pyrenoidosa) decreased from 10.18% to 3.05% and 0.75%, respectively. In conclusion, C. pyrenoidosa, as a supplement to the aquaculture systems, has practical application prospects. [ABSTRACT FROM AUTHOR]

Two kinds of culture systems were constructed, namely, an artificial substrate system (novel sponge biocarrier, SB) and a water exchange system (WE), to evaluate the effects of the microalga Haematococcus pluvialis on the water quality and performance of whiteleg shrimp (Litopenaeus vannamei). The results showed that the average NH4+-N concentration with H. pluvialis was lower than those without it. The average concentration of NO2−-N and NO3−-N in SB system were significantly decreased than those present in WE system, but there was no significant difference in SB system. The growth performance of shrimp with H. pluvialis was superior to that without it. The final average weight and growth rate of shrimp in SB1 and WE1 tanks were differed significantly among that present in SB2 and WE2 tanks (p < 0.05). SB1 tended to have the highest average weight gain and lowest feed conversion ratio. The shrimp survival was significantly higher in SB1 and WE1 tanks (89.06% and 82.29%, respectively) than that present in SB2 and WE2 tanks (78.13% and 48.44%, p < 0.05). The high-throughput sequencing results showed that the diversity of bacterial communities and the abundance of bacteria related to the nitrogen cycle and the degradation of organic matter were increased. The present study showed that H. pluvialis had positive effects on shrimp culture in using artificial substrate system and water exchange system. [ABSTRACT FROM AUTHOR]