Combined and Individual Effects of Chlorella sp. and Bacterial Probiotics in Biofloc Systems for White Shrimp (Penaeus vannamei)

This study aimed to evaluate the effects of establishing a population of the green microalgae Chlorella sp. on different key aspects of a biofloc culture of Penaeus vannamei in comparison with those obtained with a commercial probiotic. The aspects evaluated were shrimp zootechnical performance, nutritional composition of biofloc and microbial populations of shrimp intestinal microbiota and biofloc. Four treatments were tested: two of them included Chlorella sp. alone (M) or in combination to a bacterial probiotic (MP), while the other two included only the probiotic (P) or none of them (C). The presence of Chlorella sp. enhanced protein and phosphorus bioavailability in the biofloc and contributed to nutrient bioremediation within the system. However, shrimp growth performance and survival were significantly reduced, likely due to greater and more prolonged nitrate exposure following microalgae inoculation. Although overall nitrate and phosphate concentrations were higher in microalgae treatment, their accumulation over the experimental period was lower in the presence of Chlorella sp. In addition, microalgal supplementation reduced the abundance of bacterial groups associated with oligotrophic lifestyles, complex organic matter degradation, and nitrogen cycling in the intestinal microbiota. In contrast, probiotic supplementation increased protein content in shrimp and phosphorus bioavailability in the biofloc, while zootechnical performance remained comparable to the control and was higher than in microalgae treatments. Furthermore, probiotic addition reduced the abundance of Flavobacteriaceae, a bacterial family proposed as a bioindicator of White Feces Syndrome (WFS) in P. vannamei.