Temporal dynamics of the larval microbiota in hatchery-raised white seabass (Atractoscion nobilis) under probiotic and live feed manipulation

Microbial loading in hatchery-raised white seabass larvae and live feed systems is occasionally monitored through selective, culture-based methods, but comprehensive microbial characterization and tracking using next generation sequencing tools have yet to be performed. In this study, the microbiota of larval white seabass (Atractoscion nobilis) and culture water were assessed under the varying parameters of probiotic treatment, live feed selection, and time. 16S rRNA amplicon sequencing was performed to characterize bacterial microbiota within samples and achieved an average depth of 164,413 reads per sample. The factor that contributed most to larval microbiota variability was time (weighted UniFrac: n = 71, R² = 0.202, p = 0.001). Secondarily, the larval microbiota differed from their surrounding culture water (weighted UniFrac: n = 60, R² = 0.063, p = 0.001). Probiotic treatment with INVE Aquaculture’s Sanolife® MIC led to incorporation of the probiotic into the microbial community but did not impact the presence or abundance of other bacterial taxa. The probiotic treatment had no effect on larval growth or survival. Substitution of Artemia with rotifers for the first feeding did not have a significant impact on larval or culture water microbiota. Throughout larval development, the most dominant bacterial phyla in the fish were Pseudomonadota (Proteobacteria) and Bacteroidota (Bacteroidetes). Vibrio spp. peaked in larval fish during the early feeding stages (5–18 dph) and coincided with turbulence in bacterial alpha diversity. Tenacibaculum, a possible opportunistic pathogen of white seabass, was initially overrepresented in the culture water, but did not become present in the larvae until 46 dph. Neither Vibrio nor Tenacibaculum appeared to cause disease or mortality. This study helps to characterize microbial patterns in fish aquaculture, which can identify bacterial species to be monitored in consecutive life stages.