Performance of Platymonas and microbial community analysis under different C/N ratio in biofloc technology aquaculture system

Abstract

The Biofloc technology (BFT) system attracted widespread attention in aquaculture, which can reduce water replenishment with nitrogen removement, and provide extra feed. Microorganisms with complex metabolic properties played important role in bioflocs, however, the function of microalgae as a primary producer in the BFT system has rarely been studied. In this study, microalga Platymonas sp. was applied to BFT system under different carbon/nitrogen (C/N) ratio. The physiology characteristics of the microalgae, water quality parameters, and bacterial communities were monitored in seven days. At the same C/N ratio, the algae group has superior effects on removal of ammonia nitrogen, nitrite, and nitrate than the control group, and the algal group with C/N ratio of 6 achieved the same performance of control group with C/N ratio of 10. Addition of Platymonas sp. and C/N ratio also significantly (p < 0.05) affected the species diversity and richness of the flocs. In conclusion, the supplementation of the Platymonas sp. and its associated bacteria in the bioflocs performed beneficial effects on the water quality by reducing the nitrogenous compounds and providing a favorable environment for certain bacterial groups, and reduced dependence on higher content of carbon sources at the same time. Overall, this study highlights the significance of microalgae in BFT culture system under C/N ratio control.