the green macroalgae colonized the aquaculture rafts, and the fouling biomass as well as the species composition changed (Li et al., 2014; Fan et al., 2015; Wang et al., 2015). At the harvest season (April to May), U. prolifera became one of the most dominant species on the rafts, and was proven to be the source of the blooms (Fan et al., 2015; Song et al., 2015b; Wang et al., 2015). However, the propagules source of the rafts-fouling green mac-roalgae was still unclear. In our previous study, we found that the green macroalgal micro-propagules existed in the waters and sediments in the Subei Shoal area throughout a year and showed remarkable temporal and spatial variations (Song et al., 2015a). We hypothesized that they were the “seed source” of the rafts-fouling green macroalgae and could serve as the precursor of the green tides in summer. However, in that study, we did not conduct the species identification of the micro-propagules and thus could not confirm this hypothesis. In addition, the green mac-roalgal micro-propagules had strong adaptive capability to harsh environmental conditions (Zhang et al., 2011; Liu et al., 2012). When the P. yezoensis aquaculture activities were over, the farm- Foundation item: The National Natural Science Foundation of China under contract Nos 41606190 and 41506185; the Fundamental Research Funds for FIO under contract No. 2015G09; the Foundation of Key Laboratory of Integrated Monitoring and Applied Technologies for Marine Harmful Algal Blooms, SOA under contract Nos MATHAB201507 and MATHAB201806; Shandong Natural Science Foundation under contract No. ZR2016DB22. *Corresponding author, E-mail: wangzl@fio.org.cn? ers recycled the rafts and a large amount of micro-propagules attached on the ropes and bamboo poles (Song et al., 2015a). We were not sure that whether the attached micro-propagules could also serve as the source of the rafts-fouling green macroalgae in the next aquaculture cycle.
