Effect of Organic and Inorganic Fertilization on the Establishment of Nitrifying Bacteria in an Integrated Culture of Penaeus vannamei and Oreochromis niloticus and Its Interaction with the Microbial Community
Author: Raysa Pâmela Oliveira Sena (Currículo Lattes)
Advisor: Dr. Luis Henrique da Silva Poersch
Abstract
This study evaluated the effect of organic and inorganic fertilization on the establishment of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) in an integrated culture of Penaeus vannamei and Oreochromis niloticus, as well as their interaction with the microbial community. A 43-day experiment was conducted in an aquaculture greenhouse, using a culture system composed of six 20 m³ tanks and six 4 m³ tanks, in which shrimp (400 shrimp m⁻²) and juvenile tilapia (45 fish m⁻³) were stocked. The experiment consisted of two treatments with three replicates each, arranged in a completely randomized design: Chemoautotrophic treatment and Heterotrophic treatment. Identification and quantification of the phytoplankton and zooplankton communities were performed by direct microscopic counting in a sedimentation chamber at the beginning and end of the experimental period. Quantification of the nitrifying bacterial community was carried out using the fluorescent in situ hybridization (FISH) technique at both time points. At the end of the trial, shrimp and tilapia weight and survival were assessed. At the conclusion of the experiment, both treatments were dominated by flagellated protozoa. The abundance of microalgae and ciliates was higher in the chemoautotrophic treatment. The relative abundance of AOB and NOB compared to the total microbial abundance was lower than 0.1%. No significant differences were observed in AOB and NOB abundance between treatments. By the end of the experimental period, shrimp weight was higher in the chemoautotrophic treatment. Tilapia weights ranged from 171.60 to 180.80 g in the chemoautotrophic and heterotrophic treatments, respectively. The use of predominantly chemoautotrophic or heterotrophic biofloc systems does not significantly affect the establishment of AOB and NOB communities in integrated multitrophic cultures of Penaeus vannamei and Oreochromis niloticus. Both fertilization strategies are equally effective in supporting the development of the microbial loop and the nitrification process in these types of culture systems.