Large-scale blooms formed by pico-sized phytoplankton, which strongly inhibited feeding activity and growth of cultured scallops, have been recorded along the coast of Qinhuangdao in the Bohai Sea since 2009. Based on pigment profiles and clone library analysis of phytoplankton samples during the blooms, the major bloom-forming species was primarily identified as pelagophyte Aureococcus anophagefferens Hargraves et Sieburth, the causative species of intensive brown tides in the United States and South Africa. Due to the indistinct morphological features of the bloom-forming microalgae and limited knowledge on the composition of phytoplankton communities, there were still disputes concerning the causative species of the blooms. In this study, the method of high-throughput sequencing targeted 18S rDNA V4 region was used to study the composition of pico- and nano-sized phytoplankton communities in 2013 and 2014. A total of 18 groups of eukaryotic microalgae at the class level and more than 2000 operational taxonomic units (OTUs) were identified in phytoplankton samples collected from the brown-tide zone in the Qinhuangdao coastal waters. For both years, A. anophagefferens was the most dominant species during the bloom period and its maximum relative abundance exceeded 60 percent. Along with other evidence, the results further confirm that A. anophagefferens is the major causative species of the pico-sized phytoplankton blooms in the Bohai Sea. The outbreak of brown tide exhibited a strong inter-annual variation between 2013 and 2014, and an increasing dominance of dinoflagellates could be observed in the Qinhuangdao coastal waters.

自2009年以来，已在渤海秦皇岛沿海地区记录到了由皮克大小的浮游植物形成的大规模绽放，强烈抑制了进食活性和养殖扇贝的生长。基于色素剖面和浮游植物样品在克隆过程中的克隆分析，绽放，主要的绽放形成物种主要被鉴定为pelagophyte aureococcus anophagefferensHargraves et Sieburth，美国和南非的密集褐潮的病因种。由于形成水华的微藻的形态特征不明显，并且对浮游植物群落组成的了解有限，因此，关于水华的致病物种仍然存在争议。在这项研究中，以高通量测序为目标的18S rDNA V4区域的方法用于研究2013年和2014年的微微和纳米级浮游植物群落组成。在类级别上共有18组真核微藻类及更多在从秦皇岛沿海水域的褐潮带中收集的浮游植物样本中，鉴定出了超过2000种操作分类单位。两年来，按蚊是花期最主要的物种，其最大相对丰度超过60％。除其他证据外，结果还进一步证实了嗜藻按蚊是渤海微尺度浮游植物水华的主要致病物种。在2013年至2014年之间，褐潮的爆发表现出强烈的年际变化，并且在秦皇岛沿海水域发现了鞭毛藻的优势度增加。