Harmful algae blooms (HABs) are characterized for the coexistence of phytoplankton species with dynamic and complex biotic interactions (e.g., competition, symbiosis, predation, parasitism, allelopathy), that occur at fine temporal and spatial scales, and are relevant to understand the role that different species of phytoplankton play in the regulation of HABs. In this work the allelopathic effects of Margalefidinium polykrikoides (=Cochlodinium polykrikoides) and Gymnodinium impudicum on Gymnodinium catenatum were evaluated. The allelopathic abilities of M. polykrikoides and G. impudicum were investigated in bi-algal culture experiments and in trials in which target species were co-cultured, separated by a 10 μm membrane to prevent a direct cell-to-cell contact; and also by the addition of different volumes of culture media without cells. For all trials, cells of each species were harvested during exponential phase and cultured together by triplicate at three relative abundances: 1:1 (200 Cells mL^–1 of each species, G. catenatum and M. polykrikoides or G. impudicum), 2:1 (400 Cells mL^–1 of G. catenatum and 200 Cells mL^–1 of M. polykrikoides or G. impudicum), and 1:2 (200 cells mL^–1 of G. catenatum and 400 Cells mL^–1 of M. polykrikoides or G. impudicum). All bioassays were carried out by triplicate in 250 mL Erlenmeyer flasks with 150 mL of modified GSe medium with an initial inoculum of 200 or 400 Cells mL⁻¹. During experiments G. catenatum abundances were enumerated daily. In bi-algal culture experiments mortalities of G. catenatum were from 50% to 100% after 48 h of cell contact with M. polykrikoides or G. impudicum. In the case of culture media without cells, only M. polykrikoides caused a decrease in the cell abundance and growth rate of G. catenatum. Morphological changes occurred in G. catenatum when in contact with M. polykrikoides and G. impudicum, such as membrane shedding, prominent nucleus, loss of flagella, cell lysis, as well as the separation of long chains into individual cells. These results suggest that in the natural environment M. polykrikoides and G. impudicum have allelopathic interactions in G. catenatum, which could negatively affect its growth and survival, indicating that these species could displace blooms of G. catenatum.

有害藻华（HABs）的特征是浮游植物物种与动态和复杂的生物相互作用（例如竞争，共生，捕食，寄生，化感作用）共存，这些相互作用在良好的时空尺度上发生，与了解其作用有关不同种类的浮游植物在HABs的调节中的作用。在这项工作中，评估了Margalefidinium polykrikoides（= Cochlodinium polykrikoides）和Gymnodinium impudicum对裸子草的化感作用。M. polykrikoides和G. impudicum的化感能力在双藻类培养实验中以及在共培养目标物种的试验中进行了研究，并用10μm的膜隔开，以防止直接的细胞间接触；还可以通过添加不同体积的无细胞培养基来实现。对于所有试验，在指数期收获每种物种的细胞，并通过三个相对丰度一式三份一起培养：1：1（每种物种200个细胞mL ^–1，G. catenatum和M. polykrikoides或M. impudicum），2 ：1（400毫升细胞^-1的G. catenatum和200个细胞毫升^-1的M. polykrikoides或G. impudicum），和1：2（200个细胞mL的^-1的G. catenatum和400个细胞毫升^-1的M. polykrikoides或G. impudicum）。所有生物测定均在250 mL锥形瓶中加150 mL修饰的GSe培养基（初始接种量为200或400细胞mL ^-1）一式三份进行。在实验过程中，每天枚举悬链线虫的丰度。在双藻类培养实验的死亡率G. catenatum分别为从50％至100％的细胞接触48小时后M. polykrikoides或G. impudicum。在没有细胞的培养基的情况下，只有多核分枝杆菌导致细胞丰度降低，并且生长速率降低。G.悬链线。形态学变化发生在G. catenatum与之接触时M. polykrikoides和G. impudicum，如膜脱落，突出的髓核，鞭毛的损失，细胞裂解，以及长链成单个细胞的分离。这些结果表明，在自然环境中，M。polykrikoides和G. impudicum在G. catenatum中具有化感作用，可能对其生长和存活产生负面影响，表明这些物种可以取代G. catenatum的花。