Most of reported harmful algal blooms (HABs) of microalgae (75%) have been caused by dinoflagellates. Studies on the negative effects of HABs have generally focused on animals, valuable organisms in particular, and environmental factors such as dissolved oxygen and nutrients, but relatively fewer on community level, particularly that using metagenomic approach. In this study, we reported an investigation on the effects of a HAB caused by the dinoflagellate Prorocentrum donghaiense on the species diversity and community structure of the dinoflagellate sub-community via a pyrosequencing approach for the samples taken before, during, and after the bloom season of P. donghaiense in the East China Sea. We sequenced partial 28S rRNA gene of dinoflagellates for the field samples and evaluated the species richness and diversity indices of the dinoflagellate community, as a sub-community of the total phytoplankton. We obtained 800 185 valid sequences (categorized into 560 operational taxonomic units, OTUs) of dinoflagellates from 50 samples and found that the biodiversity of dinoflagellate community was significantly reduced during the blooming period in comparison to that in pre- and after-blooming periods, as reflected in the four diversity indices: the species richness expressed as the number of OTUs, Chao1 index, Shannon index (evenness), and Gini-Simpson index. These four indices were all found to be negatively correlated to the cell density of the bloom species P. donghaiense. Correlation analyses also revealed that the P. donghaiense cell abundance was correlated negatively with NO⁻₃ −N, and NO⁻₂ −N, but positively with total nitrogen (TN) and total phosphorus (TP). Principal coordinates analysis (PCoA) showed that the community structure of dinoflagellates was markedly different among the different sampling periods, while the redundancy analysis (RDA) revealed P. donghaiense abundance, salinity, NO⁻₂ −N, and SiO²₃ were the most four significant factors shaping the dinoflagellate community structure. Our results together demonstrated that HABs caused by the dinoflagellate P. donghaiense could strongly impact the aquatic ecosystem on the sub-community level which the blooming species belongs to.

中文翻译：

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东海原藻的开花减少了鞭毛藻群落的物种多样性

大多数报道的微藻有害藻华（HAB）（75％）是由鞭毛鞭毛虫引起的。关于HAB负面影响的研究通常集中在动物，尤其是有价值的生物以及诸如溶解氧和营养素等环境因素上，但是在社区层面上的研究相对较少，特别是使用宏基因组学方法。在这项研究中，我们报告了通过热测序方法对开花季节之前，期间和之后采集的样品进行的鞭毛东海原鞭毛原螯虾引起的HAB对鞭毛亚群落亚种的物种多样性和群落结构的影响的调查。的东海原甲藻在东海。我们对野鞭毛藻的部分28S rRNA基因进行了测序，并评估了鞭毛藻群落的物种丰富度和多样性指数，将其作为总浮游植物的一个亚群落。我们从50个样本中获得了800 185个有效的鞭毛藻序列（归类为560个操作生物分类单位，OTU），发现与开花前和开花后相比，鞭毛藻在盛花期的生物多样性显着降低，因为反映在四个多样性指数中：以OTU数量表示的物种丰富度，Chao1指数，Shannon指数（均匀度）和Gini-Simpson指数。发现这四个指数均与开花物种P. donghaiense的细胞密度呈负相关。。相关分析还显示，东海假单胞菌细胞丰度与NO ^- ₃ -N和NO ^- ₂ -N呈负相关，但与总氮（TN）和总磷（TP）呈正相关。主坐标分析（PCoA）表明，鞭毛藻的群落结构在不同采样周期之间存在显着差异，而冗余度分析（RDA）表明东海参的丰度，盐度，NO ^- ₂ -N和SiO ² ₃最多。塑造鞭毛虫群落结构的四个重要因素。我们的结果共同表明，由鞭毛鞭毛虫引起的HABs 可能会在开花物种所属的亚群落水平上强烈影响水生生态系统。