:Phaeocystis globosa is one of the dominant microalgae associated with harmful algal blooms (HABs). P. globosa has a pleomorphic life cycle and its ecological success has been attributed to algal colony formation. However, few studies have assessed differences in functional profiles and microbial communities between the inside- and outside-colonies. To address this, environmental and metagenomics tools were used to conduct a time-series analysis of the bacterial composition and metabolic characteristics of intra- and extra-colonies during a natural P. globosa bloom. The bacterioplankton structure and functions were shown to exhibit significant temporal heterogeneity throughout the bloom phases (pre-, during- and post-stage). A distinct difference was also found between the intra- and extra-colonies. Intra-colony bacterial functional genes were more enriched in matter metabolic and signal communication pathways. The conception model shows that functional potential and microbial composition are remarkably related to algal bloom fate, especially in the intra-colonial environment. Overall, this work highlights the differences in bacterial structure and functions within and outside the colony during algal blooms. The findings provide fundamental information to better understand that phenotypic heterogeneity is a selective strategy that improves population competitiveness and environmental adaptation, benefiting P. globosa bloom formation and persistence.
 

Phaeocystis globosa,Colony,Algal blooms,Microbial profiles,Ecological strategy