The underlying mechanisms of bacterioplankton community assembly and interspecies interactions during harmful algal blooms remain largely unclear. Using 16S rRNA gene amplicon sequencing, we analyzed the bacterioplankton communities over the continuous course of saxitoxin-producing Gymnodinium catenatum blooms and two diatom (i.e., Skeletonema costatum and Chaetoceros curvisetus) blooms in an anthropogenically controlled and eutrophic bay, East China Sea. The succession of bacterioplankton communities correlated with changes in the dynamics of algal species. Deterministic versus stochastic bacterioplankton community assemblage processes were quantified, demonstrating that stochastic processes increased when algal blooms happened. The occurrence of algal blooms caused weaker bacterioplankton interspecies interactions and higher degrees of cooperative activities, changed keystone taxa and diminished the stability of bacterial communities. These findings consequently have important implications for our understanding of bacterioplankton community ecology during algal blooms.

在有害藻华期间，浮游细菌群落组装和种间相互作用的潜在机制仍不清楚。使用16S rRNA基因扩增子测序，我们分析了产生毒素的连续过程中浮游生物群落，其中Gymnodinium catenatum花朵和两个硅藻（即，Skeletonema costatum和Chaetoceros curvisetus））在一个由人为控制且富营养的海湾东海盛开。浮游细菌群落的演替与藻类动力学变化有关。确定性和随机的浮游生物群落组装过程被量化，表明当藻华发生时，随机过程增加。藻华的发生导致浮游植物之间的物种间相互作用较弱，合作活动程度更高，改变了梯形分类群并降低了细菌群落的稳定性。因此，这些发现对我们理解藻华期间浮游细菌群落生态学具有重要意义。