Differential response patterns of bacterial communities in seawater and sediments to the Chaetomorpha valida bloom in sea cucumber Apostichopus japonicus aquaculture ponds.

The microbiota play a critical role in the health of the aquaculture pond ecosystem. Green tide have been found to affect the microbial community in the marine environments, but effects of Chaetomorpha valida bloom on the microbial composition in the aquaculture ponds related to the marine economic species have been rarely investigated. To address this shortcoming, we provided baseline information on the bacterial composition and diversity in C. valida bloom areas and non-bloom areas of Apostichopus japonicus aquaculture ponds in four seasons. High-throughput 16S rRNA sequencing revealed that C. valida bloom significantly changed the bacterial community composition in seawater and bacterial richness in sediment, but has minor effects on sediment bacterial community structure. The co-occurrence network analysis indicated that the bloom of C. valida intensified interspecific competition among sedimentary bacteria, thereby enhancing their stability. In contrast, it promoted symbiotic relationships among bacteria in seawater. Importantly, there were higher proportions of potential pathogens in seawater from C. valida bloom areas compared to non-bloom areas, suggesting a higher ecological risk associated with the C. valida blooms. This study offers novel perspectives on how bacterial communities in sediments and seawater differently respond to C. valida bloom in aquaculture systems.