How natural bacterioplankton communities respond to environmental changes after inoculation with an algicidal material, to mitigate Cochlodinium polykrikoides blooms: Assessment using microcosm experiments

Abstract

The aim of the present study was to determine how bacterioplankton communities change when Cochlodinium polykrikoides blooms are subject to control following the introduction of the algicidal material Ca-aminoclay, and to clarify whether the compositions of the bacterioplankton communities are species-specific for phytoplankton. Specifically, we analysed changes in the genetic diversity of bacterioplankton communities using 454 pyrosequencing in sub-samples obtained from in situ microcosm experiments containing natural C. polykrikoides blooms and the natural phytoplankton community. It was noted that Alpha-proteobacteria and Bacteroidetes were strongly associated with the blooming stage of C. polykrikoides, suggesting that these bacterioplankton groups are intimately linked to the development of C. polykrikoides blooms. In contrast, Gamma-proteobacteria were associated with the termination of harmful algal blooms and hypertrophic environmental conditions due to the algicidal material Ca-aminoclay. In water containing C. polykrikoides blooms, the bacterioplankton community exhibited marked differences for example, Phaeobacter caeruleus (Alpha-proteobacteria) formed a large proportion of all the bacterioplankton communities, while Tenacibaculum aestuarii and Flavobacterium aquidurense (Bacteroidetes) increased during the early stages of C. polykrikoides bloom decline. Our results suggest that the composition of bactere compositions of the bacterioplankton communities are species-specific for phytoplankton. Specifically, we analysed changes in the genetic diversity of bacterioplankton communities using 454 pyrosequencing in sub-samples obtained from in situ microcosm experiments containing natural C. polykrikoides blooms and the natural phytoplankton community. It was noted that Alpha-proteobacteria and Bacteroidetes were strongly associated with the blooming stage of C. polykrikoides, suggesting that these bacterioplankton groups are intimately linked to the development of C. polykrikoides blooms. In contrast, Gamma-proteobacteria were associated with the termination of harmful algal blooms and hypertrophic environmental conditions due to the algicidal material Ca-aminoclay. In water containing C. polykrikoides blooms, the bacterioplankton community exhibited marked differences for example, Phaeobacter caeruleus (Alpha-proteobacteria) formed a large proportion of all the bacterioplankton communities, while Tenacibaculum aestuarii and Flavobacterium aquidurense (Bacteroidetes) increased during the early stages of C. polykrikoides bloom decline. Our results suggest that the composition of bacter