Closely related responses of Environments-Virus-Bacteria on Akashiwo sanguinea (Dinophyta) HABs from blooms to termination for in-door microcosm study

Abstract

We investigated the ecological responses of marine virus, bacterial and eukaryotic plankton communities by metagenomics during and after Akashiwo sanguinea (Dinophyta) harmful algal blooms (HABs) for 100 L scale in-door microcosm study (continuous supply of inorganic nutrient sources optimal growth temperature suitable for optimal growth conditions). With the decrease and termination of A. sanguinea bloom, the concentrations of the inorganic nutrients, in particular, phosphate and ammonia increased rapidly. Changes in the concentration of dissolved organic carbon were similar to those of the phosphate and ammonia concentrations. A. sanguinea bloom harboured and promoted specific bacterial populations. Particularly, the host-specific bacterial OTUs (Polaribacter marinivivus and Polaribacter huanghezhanensis) that remineralizes extracellular products from A. sanguinea participates in micro-environments and plays an important role in microbial community dynamics. Among nucleocytoplasmic large DNA viruses (NCLDVs), Aureococcus anophagefferens virus was strongly and positively correlated with the HABs, Amoebophrya sp. The endoparasitic dinoflagellate Amoebophrya sp. has attracted attention regarding its roles in trophic interactions: the endoparasitic dinoflagellate Amoebophrya sp. controlled the bloom dynamics and correlated with HAB decline. Thus, microbial communities and the environment changed dynamically during the A. sanguinea bloom, and the rapid turnover of microorganisms responded to ecological interactions. A. sanguinea bloom dramatically changes the environments by exuding dissolved carbohydrates via autotrophic processes, followed by changes in microbial communities involving host-specific viruses, bacteria and parasitoids. Moreover, to interpret their ecosystem, the complex reactions among various microorganisms should be studied rather than evaluated a simple 1:1 reaction, such as a prey–predator interaction.