Temporal and spatial dynamics of algicidal and growth-inhibiting bacteria against the fish-killing raphidophyte Chattonella antiqua in seawater of Yatsushiro Sea, south-western Kyushu, Japan
稲葉, 信晴 ,
秋里, 綾乃 ,
黒田, 麻美 ,
西, 広海 ,
田原, 義雄 坂見, 知子 ,
18 , 2016-03-18 , 北海道大学大学院水産科学研究院
The harmful raphidophyte Cattonella antiqua is known as a notorious red-tide causing autotrophic flagellate. Mass mortalities of mainly cultured yellowtails by C. antiqua in 2009 and 2010 at Yatsushiro Sea, located in Kyushu, the southernmost of the four main islands of Japan, reaching 8.7 billion Japanese yen(about 80 million US dollar) have been newly reported. There is an urgent need to seek strategies for reducing negative impacts by Chattonella red-tides. In this study, temporal and spatial fluctuations of algicidal bacteria(AB) and growth-inhibiting bacteria(GIB) against C. antiqua in the seawater at southwest of Yatsushiro Sea were investigated in 2012. Densities of AB or GIB ranged between 3.7×10¹-5.6×10³CFU mL⁻¹ at 0 m and 1.4×10¹-8.5×10²CFU mL⁻¹ at 1m above the bottom(B-1m). Percentages of bacteria that killed or inhibited the growth of C. antiqua within the total culturable bacteria fluctuated between 3.3-17%(0m) and 3.3-10%(B-1m). AB and GIB were mostly found as particle-associated form(0m : 71%, B-1m : 87%). Partial 16S rRNA sequencing revealed that all of AB and GIB detected in this study were comprised of α- and γ-proteobacteria as well as the previous study conducted in 2011. This study gives an important ecological implication of algicidal and growth-inhibiting bacteria in coastal water in relation to the occurrences and prevention of harmful red-tides by Cattonella spp.