Bacterial Communities in the Water of Larval-Rearing System for the Yesso Scallop (Patinopecten Yessoensis)

Bacterial disease is a significant issue for larviculture of the Yesso scallop (Patinopecten yessoensis). One source of bacteria is the water of larval-rearing tanks. In this study, water bacterial communities were investigated by MiSeq sequencing during larval development at fertilized egg W1, trochophora W2, D-shaped larvae W3, umbo larvae W4, juvenile scallop W5 stages. Genomic DNA was extracted from the water samples, and a gene segment from the V3-V4 portion of the 16S rRNA gene was amplified and sequenced using an Illumina Miseq sequencer. A total of 69245 optimized reads obtained from five samples were identified as 9 phyla and 86 genera. Bacterial communities were dominated by the Proteobacteria and Bacteroidetes at phylum level across five larval development stages. At genus level, sequences assigned to Pseudoalteromonas, NS3a marine group and Sulfitobacter were dominant at stages of W1, W4 and W5. Moreover, reads from Vibrio became dominant at stage W2, followed by Pseudoalteromonas and Sulfitobacter; Glaciecola was dominant at stage W3, followed by NS3a marine group and Sulfitobacter. These findings indicated that water bacterial communities changed greatly during the trochophora and D-shaped larvae stages of larval development.