Bacterial community temporal dynamics and disease-related variations in the seawater of Pyropia (laver) seedling pools

Conchocelis cultivation is a crucial step in the industrial growth of Pyropia (laver). However, our knowledge of the seawater microbiology community in Pyropia seedling pools is limited. This study investigated the temporal dynamics in seedling pool microbiota before and after outbreaks of yellow spot disease in Pyropia yezoensis conchocelis. A total of 18 water samples were collected to assess seedling pool health status, followed by the sequencing of microbiota 16S ribosomal RNA (rRNA). Analysis of 16,760,224 16S rRNA gene sequences indicated that the core microbe group comprised 207 genera. The microbial diversity of samples gradually increased from May to July. The bacterial diversity of seawater samples from diseased P. yezoensis seedling pools was significantly higher than samples from healthy seedling pools. It is noteworthy that each pool group had a distinctive microbial community composition. The relative abundance of two dominant bacteria genera, Sediminicola and Roseivirga, increased over time in healthy seedling pools, peaking in August, while Vibrio remained at constantly low levels. However, the abundance of Vibrio and Polaribacter increased sharply in diseased P. yezoensis seedling pools and decreased after fresh seawater exchange. This indicates that these bacteria are probably associated with the filament disease. Many disease-associated bacteria are negatively related to the HCO3 − concentration in seawater and positively related to pH. Changes in bacteria and environmental factors reflect the characteristics of microbial community succession in seedling pools and therefore have potential to be used as biomarkers and environmental signals for Pyropia disease monitoring.