Seasonal changes in picocyanobacterial diversity as revealed by pyrosequencing in temperate waters of the East China Sea and the East Sea

Abstract

To elucidate the seasonal and spatial changes in picocyanobacterial diversity in temperate waters, the abundance and genetic diversity of picocyanobacteria and environmental variables were investigated at 3 stations located in the East China Sea and the East Sea. Barcoded amplicon pyrosequencing of 16S-23S internal transcribed spacer sequences was applied to study picocyanobacterial diversity using 36 samples. Through pyrosequencing, sequences belonging to 27 distinct Synechococcus and Prochlorococcus clades were retrieved, which showed high picocyanobacterial diversity and obvious seasonal variation in marginal waters. The coastal and cold water-adapted Synechococcus Clades I and IV were dominant during winter and spring, whereas the warm water-adapted Synechococcus Clade II and Prochlorococcus HLII ecotype were dominant during the summer and autumn. Further, Synechococcus Clades III, V, VII and 5.3-I as well as Prochlorococcus LLI opportunistically occupied distinct niches in the summer and early winter. In these temperate marginal seas, the seasonal distribution of picocyanobacterial diversity was mainly controlled by temperature and nutrient level. In addition, the seasonal circulation pattern of adjacent water masses was a key determinant of the physicochemical properties of water and consequently of picocyanobacterial diversity.