Molecular identification of the macroalgae that cause green tides in the Bohai Sea, China

In 2015, a novel green tide began to bloom in Qinhuangdao on the coast of the Bohai Sea, northern China, and has recurred each April to September since. Accurate identification of the causative species of the green tides is the first step in studying this marine ecological disaster. In this study, fifteen green macroalgal samples and nine red macroalgal samples were collected according to the development process of the green tide. Seven gene markers, ITS, rbcL, tufA, and 5S spacer and COI, LSU, and UPA were co-employed to classify the species in the green and red macroalgae, respectively. In a comprehensive analysis of the molecular identification results and the morphological characteristics of the macroalgae, Ulva pertusa, Bryopsis plumosa, and Ulva prolifera, respectively, were confirmed to be the first dominant species in the three distinct stages of the green tide. In addition, we also found that the rbcL and COI genes can serve as the appropriate gene markers for molecular identification of the green and red macroalgae, respectively, in the Bohai Sea green tide.