Heterotrophic, chemoautotrophic and mature approaches in biofloc system for Pacific white shrimp

Abstract

This work aimed to evaluate three different strategies for rearing L. vannamei in a biofloc system: heterotrophic, chemoautotrophic and a mature biofloc system relative to the effects of water quality, water bacterial community, biofloc composition and yield. To accomplish this, a study lasting 35 days was conducted with juvenile (3.46 g) shrimps stocked in twelve 300 L tanks at a stocking density of 350 shrimp m3. For heterotrophic treatment, water received molasses as a carbon source. For chemoautotrophic treatment, ammonium and nitrite salts were added to the water. The mature treatment was created by adding a significant amount of water containing mature biofloc from another established biofloc technology (BFT) system. In both mature and chemoautotrophic treatments, the nitrification process could maintain toxic nitrogen compounds (ammonia and nitrite) at low levels without the addition of carbohydrates. In contrast, the heterotrophic system had peaks of ammonia and nitrite during the rearing cycle. The heterotrophic system also had a significantly higher value of volatile solids and total suspended solids compared to the other treatments. Analysis of the biofloc system revealed a relatively high proportion of protein, but the proportion of protein in the heterotrophic system was higher. Chemoautotrophic and mature treatments maintained the water quality at a constant level, especially nitrogen removal. Metagenomic analysis showed the microbial community associated with the biofloc system to be represented by 10 phyla. In all treatments, the five most abundant phyla were the following: Proteobacteria, Bacteroidetes, Chloroflexi, Actinobacteria, and Gemmatimonadetes. Shrimp performance demonstrated that heterotrophic, mature and chemoautotrophic systems are suitable approaches for shrimp rearing in BFT.