북서태평양 주변해에서 Synechococcus lineage의 시공간적 변화

Abstract

To understand seasonal distribution of pico-cyanobacteria and to elucidate factors regulating their distribution, abundances and clone diversity and environmental variables were investigated for the East China Sea and the East Sea. Synechococcus were found to be predominant. Prochlorococcus, however, was a dominant member in only October in the East China Sea. There were 18 distinct Synechococcus clades, three of which were novel clades. Synechococcus lineages showed a clear seasonal distribution pattern. Clades I, IV and WPC3 were dominant in winter or spring, whereas clades II, WPC1, WPC3 and sub-cluster 5.3 (formerly clade X) were dominant in summer or autumn. Distinct vertical distribution patterns were observed in summer when thermal stratification is strong. Based on the T-RFLP analysis, distinct lineages of Synechococcus were shown between surface and sub-SCM depths. Thus, seasonal variations of Synechococcus lineages seemed to be due to seasonal temperature changes, and vertical variations especially in warm seasons reflected water temperature differences by water column stratification. In addition, spatial variations of Synechococcus lineages among stations suggested that mixing of water masses could be important in the variation.