Abstract:

The bioflocs shrimp culture system was used to culture M. japonicus and investigate the efficiency and stability of nitrogen conversion in the biofloc system during abrupt temperature change. In the experiment, M. japonicus was randomly divided into 2 groups. The control group was disinfected clean seawater with a daily water exchange rate of 20% (semi-closed culture system), and the experimental group was biofloc seawater with an initial volume of 20 mL/L (biofloc floc culture system). After the water quality of the experimental group and the control group remained stable for one week, the temperature mutation stress was applied, and the temperature rose sharply by 10℃. The results showed that there was no significant effect of abrupt temperature change on the nitrogen conversion pathway in the biofloc system during the experiments, and the nitrate nitrogen in the experimental group showed an increase after abrupt temperature change, from 19.65 mg/L on the 5 d of the experiment (before abrupt temperature change) to 31.54 mg/L on the 10 d (after abrupt temperature change), and the cumulative rate was greater in the experimental group than in the control group. High-throughput sequencing revealed that a total of 4219 OTUs were obtained in both experimental and control aqueous organisms. The abundance and diversity indices were greater in the experimental group than those in the control group, and greater before than after abrupt temperature change. Microbial communities in the water and gut after temperature mutation were lower in abundance and diversity than before abrupt temperature change. Bioflocs system performed better than semi-closed culture system in coping with abrupt temperature change, with higher stability in both abundance and diversity of microbial communities.

Key words: biofloc, nitrogen conversion, microbial community, temperature mutation