A newly recorded species of freshwater blooming dinoflagellates from China and its ecological risks

Abstract

2019年6月，在山东省峡山水库多个位点采集到角藻属（Ceratium）样品，并发现其在局部位点形成明显的浅褐色水华.系统发育分析结果显示该种与角藻属常见种飞燕角藻（C.hirundinella）亲缘关系最近，但形态学上有明显区别，前者具有1块间插板和3个顶板，而飞燕角藻具有4块顶板.通过对比，发现该种为我国淡水甲藻门未经描述的新记录物种——拟二叉角藻（C.furcoides）.峡山水库中，水华发生位点的水体叶绿素a浓度高达125.77 μg/L，拟二叉角藻的密度达1.23×10⁶ cells/L，占总藻细胞密度的1.21%.细胞数量上，占优势的主要是尖头藻（Merismopedia spp.）和浮丝藻（Planktothrix spp.）等一些丝状蓝藻；但因个体细胞体积非常大，鲜重高达86.31 mg/L，占总藻鲜重的49.34%，因此在生物量上拟二叉角藻是绝对优势种.此外，通过核查采自我国东北、华中、西南地区不同时期、温度较高季节的多个标本，基于其自身特性和分布特点，本研究认为拟二叉角藻偏好高温和富营养水体，有在我国不同地区水体扩张并形成水华的潜在能力.;In recent years,dinoflagellate blooms had occurred frequently, and most of them were caused by the species of genus Peridinium and Peridiniopsis, and caused by the species of genus Ceratium were rare. Recently, however, the genus Ceratium species had been found throughout the world in the water bodies such as eutrophic reservoirs and fish ponds. In June 2019, some samples of the genus Ceratium were collected at various sites in Xiashan Reservoir of Shandong Province and found that it formed obvious light brown water blooms at local sites. Phylogenetic analyses showed that this species had the closest relationship with the common species C. hirundinella of the genus Ceratium, but the morphologically, the former had one intercalary plate and three apical plates, which were different from the C. hirundinella with four apical plates. By contrast, it is a newly recorded species of dinoflagellates-C. furcoides, which do not have been described in China. It has been reported as an invasive and water blooming species, which is often found in eutrophic water bodies during high-temperature seasons. In the Xiashan Reservoir, the chlorophyll-a concentration at the bloomed site is as high as 125.77 μg/L, and the density of the C. furcoides is 1.23×10⁶ cells/L, accounting for 1.21% of the total algal cell density. The number of cells is dominated by some filamentous cyanobacteria such as Merismopedia spp. and Planktothrix spp.; however, due to the very large individual cell size of the C. furcoides, its fresh weight is as high as 86.31 mg/L, accounting for 49.34% of the total algae fresh weight, which is the absolute dominant species in biomass. In addition, by examining multiple specimens collected from northeast China, central China, and southwest China in different periods during high-temperature seasons, based on its own and distribution characteristics, we held that C. furcoides preferred the high temperature and the eutrophic waters, and it has the potential ability to expand and form water bloom in different areas of China.