Dynamics of seagrass bed microbial communities in artificial Chattonella blooms: A laboratory microcosm study

The influence of algicidal and growth-inhibiting bacteria in a seagrass (Zostera marina) bed, and their capability of controlling blooms of the fish-killing raphidophyte flagellate, Chattonella antiqua, were examined in laboratory microcosm experiments. Bacterial communities in seawater collected from the seagrass bed and Z. marina biofilm suppressed artificial Chattonella blooms in the presence of their natural competitors and predators. Phylogenetic analysis suggest that considerable numbers of bacteria that suppress Chattonella, including algicidal or growth-inhibiting bacteria isolated from seagrass biofilm and seawater from the seagrass bed, are members of Proteobacteria that can decompose lignocellulosic compounds. A direct comparison of partial 16S rRNA gene sequences (500 bp) revealed that the growth-limiting bacterium (strain ZM101) isolated from Z. marina biofilm belonged to the genus Phaeobacter (Alphaproteobacteria) showed 100% similarity with strains of growth-limiting bacteria isolated from seawater of both the seagrass bed and nearshore region, suggesting that the origin of these growth-limiting bacteria are the seagrass biofilm or seawater surrounding the seagrass bed. This study demonstrates that Chattonella growth-limiting bacteria living on seagrass biofilm and in the adjacent seawater can suppress Chattonella blooms, suggesting the possibility of Chattonella bloom prevention through restoration, protection, or introduction of seagrass in coastal areas.