Spatial and diel variations of the prokaryotic community in the Phaeocystis globosa blooms area of Beibu Gulf, China

While prokaryotes play key roles in nutrient cycling and energy flow during Phaeocystis globosa blooms, the information on the spatial and diel temporal distribution of the prokaryotic community during Phaeocystis blooms remains scarce. In January 2019, we used high-throughput sequencing of the 16S rRNA gene to explore the spatial and diel variations of particle-attached (PA) and free-living (FL) prokaryotic communities during the blooming phase of P. globosa in Beibu Gulf, Guangxi, China. The results suggested a significant spatial variation pattern in the horizontal distribution of prokaryotic communities, while there was no significant difference in the vertical direction. Both spatial distance and environmental variables shaped the horizontal distribution of the prokaryotic community structure, while environmental variables, particularly the abundance of P. globosa colony and Chl a , showed more significant influence and were closely related to the structure and variation of the prokaryotic community. Strong vertical mixing of the water column disrupted the vertical structure heterogeneity of the prokaryotic community in winter. There were significant differences in the diel samples of PA prokaryotic communities, but not in the FL prokaryotic communities. Nitrate, ammonium and the abundance of P. globosa colony were the key environmental variables impacting the diel variations of prokaryotic communities over the sampling period. The present study provided valuable information to depict the spatial-temporal variations of the microbial community and its association with environmental parameters during P. globosa bloom in the tropical gulf.