壬基酚对珠江口赤潮藻种间竞争的作用机制研究

The increasing contamination of nonlyphenol (NP) and harmful algae blooms (HABs) have been considered as the key environmental challenges in the Pearl River Estuary. Lots of studies were focused on water quality deterioration and economic decrease caused by pollutants and HABs, however, biological response was limited to single species. Therefore, it is emergency to understand the relationships between NP pollution and HABs dynamics, which uncovers the coevolution trend of environment-organism in the Pearl River Estuary. Four harmful algae, Cochlodinium geminatum, Skeletonema costatum, Phaeocystis globosa and Rhizosolenia sp. isolated from Zhuhai will be investigated in this study. Impact of NP concentrations on interspecific competition of these four algae will be determined and interspecific competition between C. geminatum and other species with different inoculation ratios will be further studied. The results will explore biological and ecological regulations of HABs in the Pearl River Estuary and the relationships between NP pollution and harmful algae dynamic. Furthermore, toxicity of NP will be evaluated through both short term acute test and long term exposure. Metabolic characters of NP in four algae and effect of NP on synthesis and activity of allelochemicals will be studied. The combined effect between NP and allelochemicals will be evaluated by detecting whether and how those combined substances affected in harmful algae succession. Upon completion of this project, it will help to understand environmental behavior of NP and its ecological risks in the Pearl River Estuary. It is beneficial to explain the relationships between bloom of C.geminatum and NP pollution scientifically.

珠江口壬基酚污染和有害藻类赤潮频发等问题是环境领域研究的热点。壬基酚污染过程与赤潮藻种类演变相关性研究的迫切性不仅体现在其理论价值，而且对珠江口海域环境-生物响应的演变趋势预警具有重要的现实意义。项目选择分离自珠海海域的四种典型赤潮藻，开展室内模拟实验研究壬基酚浓度对赤潮藻种间竞争的干扰效应及壬基酚对不同组合种类和比例下双胞旋沟藻竞争结果的影响。对比分析珠江口赤潮藻种类演变的生物学差异和壬基酚作用规律。进而开展壬基酚对赤潮藻生理生化特征的影响、壬基酚在赤潮藻中的代谢动力学以及壬基酚对赤潮藻化感物质合成和抑藻活性的干扰作用研究，阐明壬基酚污染过程与有害藻类赤潮演变现状的关联性，揭示壬基酚暴露和化感作用在赤潮藻种类演变过程中的复合效应类型和生物化学机制。研究结果将为揭示壬基酚等新兴污染物的环境行为提供基础资料，为认识珠江口海洋污染现状与双胞旋沟藻赤潮频发的关联性这一科学问题提供实验依据。

以四个门类海洋微藻为研究对象，测定了壬基酚（nonylphenol，NP）对其生理生化指标的作用特征、NP的代谢动力学规律，评估了赤潮藻种类演变的生物学差异性和NP的干扰效应特征。重点探索了NP暴露浓度对微藻种间竞争的干扰效应、NP对不同起始比例下微藻种间竞争的作用规律，对球形棕囊藻、米氏凯伦藻和锥状斯氏藻种间竞争的化感作用进行了初探。主要研究结论如下：（1）NP对藻类生长的抑制作用大小顺序为：中肋骨条藻>牟氏角毛藻>棕囊藻>凯伦藻。NP对叶绿素荧光显著抑制的浓度阈值介于5~63 μg/L。（2）藻液中NP的去除速率大小顺序为：凯伦藻>骨条藻>角毛藻>棕囊藻，NP去除速率与细胞粒径呈正相关关系，且符合一级反应动力学特征。（3）以f/2培养，生长速率的大小顺序为：棕囊藻>骨条藻>亚心形扁藻>凯伦藻>斯氏藻。两两混合培养下，扁藻的生长速率比单一培养增加了25.49%~92.16%，表现出了显著的竞争优势。凯伦藻、斯氏藻与骨条藻混合培养下也表现出了促进生长的现象。（4）天然海水培养，生长速率的大小顺序为：棕囊藻>骨条藻>凯伦藻>斯氏藻。混合培养微藻的种间竞争能力大小顺序为：斯氏藻>凯伦藻>骨条藻>棕囊藻。（5）低浓度（1.7、10 μg/L）NP对单一培养的斯氏藻、凯伦藻和骨条藻具有促进作用，对混合培养的棕囊藻具有抑制作用，但40 μg/LNP对混合培养的微藻均具有抑制作用，NP暴露显著影响了种间竞争结果。（6）棕囊藻、骨条藻起始密度增加，混合培养微藻对棕囊藻、骨条藻的抑制效应降低，但棕囊藻与斯氏藻起始比例500:1时仍受到显著的抑制作用。（7）微藻种间竞争结果与微藻组合以及NP浓度、微藻耐受性有关。相同起始密度下，NP浓度增加，对斯氏藻和凯伦藻竞争有利，对棕囊藻和骨条藻的抑制作用增加。棕囊藻和骨条藻起始密度增加，不仅增加了其种间竞争能力，同时降低了NP暴露对其抑制作用，从而有利于其种间竞争。（8）棕囊藻、凯伦藻、斯氏藻培养末期的滤液、藻细胞内均存在抑制藻类生长的物质，化感物质的抑制效应强弱在破碎滤液处理组>破碎液组>滤液组。凯伦藻分泌到胞外的化感物质对自身细胞影响显著低于其他种类微藻，表现出了选择性抑制效应，其余组分的微藻化感物质对自身细胞生长也表现出显著的抑制效应。