Characterization of the bacterial microbiota associated with the formation of flocs and in the nitrification process in intensive production systems (Biofloc Technology - BFT) of the white shrimp Litopenaeus vannamei
Bacteria have several crucial functions for the successful production of aquatic organisms using biofloc technology (Biofloc Technology - BFT), however, our knowledge about the diversity and activity of bacteria has been limited mainly by the lack of more efficient techniques for characterization of these bacterial communities. Therefore, the objective of this work was to analyze the diversity of the bacterial community involved in the formation of bioflocs and in the nitrification process in aquaculture systems using the BFT system and the addition of artificial substrates for the formation of biofilm during intensive production of white shrimp Litopenaeus vannamei. For this it was necessary to implement a technique of analysis of bacterial diversity for aquaculture systems, in this case, the fingerprinting technique Temporal Temperature Gradient Electrophoresis (TTGE). In this work it was possible to observe that the biofilm serves as a food supplement and reduced the stress caused by the high stocking density, improving the zootechnical performance of the shrimp, however, the addition of artificial substrates in the production environment did not influence nitrification. This was more influenced by the reuse of water with bioflocs, accelerating the oxidation of ammonia to nitrite. Another factor that influenced the nitrification process was the intensity of water mixing (turbulence), controlling the size of the bioflocs. It was observed that the use of porous stones presented less mixing intensity and allowed the formation of bioflocs of larger size and greater efficiency in nitrification than with the use of aerotubes in the production tanks, which presented greater intensity of mixing, but smaller and less efficient nitrification, demonstrating the importance of turbulence in the size of bioflocs in the BFT system. The TTGE technique was effective for analyzing the diversity and succession of the bacterial community of bioflocs and biofilm in a BFT system, being able to be applied in different aquaculture systems. The use of this technique, combined with environmental data during the production cycle of L. vannamei, made it possible to infer bacterial ribotypes related to the formation of bioflocs and the nitrification process. Besides that, it was observed that the bacterial communities of the biofloc and biofilm are similar to each other.