珠江颗粒直链藻形态多样性机制及其对水体营养等级的指示功能

Aulacoseira granulata, a cosmopolitan centric diatom species from freshwater areas, is always regarded as an important indicator to water eutrophication. In recent years, the ecological characteristics of A. granulata in the main stream and estuary of the Pearl River have been reported by the applicant, and its predominant position in phytoplankton community is also confirmed. In addition, we also find that morphological variety of A. granulata varies significantly with different eutrophic levels, and the filament shape in eutrophic conditions even beyond the definition of < Flora Algarum Sinicarum Aquae Dulcls >, thus leading to the species identification confused. Therefore, it is necessary to pay special attention to the mechanisms of morphological variety of Aulacoseira granulata and its indicating function to water quality, since cell dimensions and filament shape could be visual and sensitive with the changing water environment. This project plan to make supplementary survey in several sections representing different nutrient levels of the Pearl River and to verify the prior assumption, based on our previous ecological studies. Meanwhile, we will combine the methods of ecological studying and laboratory culturing, since the ecological results could direct the process of laboratory culturing, and the latter could test the ecological conclusions. In this way, we could not only confirm the key external causes, but the internal mechanisms as well; and then we could conclude the indicating role of the morphology variety by reverse thinking. Above all, the research achievement will not only provide technical support for the identification work and sufficient materials for refresh work of < Flora Algarum Sinicarum Aquae Dulcls >, but also serve for the aquatic ecological study.

颗粒直链藻是内陆水体富营养化的重要指示藻种，其在珠江中下游水域浮游植物群落中占据绝对优势。申请者发现，不同营养水体中，颗粒直链藻的形态多样性差异显著，尤其在富营养化水体中形态多样性极其丰富，甚至超出了国内分类志书所界定的范围。申请者认为颗粒直链藻的形态多样性对水体营养状况具有较好的指示功能，有必要对其形态多样性机制及水质指示功能进行针对性研究。本课题拟在前期调查研究基础上，对珠江不同营养江段进行补充调查，验证前期对该藻形态多样性与水体营养状况存在关联的预判，同时结合野外原位培养和室内培养试验，研究颗粒直链藻形态多样性的发生与水体理化因子的关系，确定关键外因；并对不同形态进行分离培养观察，研究形态转换的可能性并探索内在机制。研究成果不仅可以服务于水域生态环境研究，为水环境指示和预警开拓新的思路；也可丰富颗粒直链藻形态学方面的研究，为分类学研究提供科学资料支持。

本项目基于野外生态调查和实验室培养研究，并引入文献计量分析和模型技术，较全面地研究了珠江中下游水域颗粒直链藻形态多样性机制及其对水体营养等级的指示功能。主要研究结论如下：（1）基于文献计量分析的结果发现，欧美发达国家对直链藻学术论文的贡献最大，在国际合作方面也处于领先地位。有关直链藻的研究内容仍偏重于基础性研究，分类、多样性和种群生态学方面的研究仍保持一定的热度。淡水湖泊和江河流域是开展直链藻研究的主要区域。（2）采用扫描电镜（SEM）技术，发现珠江中下游水域有两种直链藻具端刺，分别为颗粒直链藻和赫组基直链藻，对2个物种的形态特征进行了观察和描述，并与其它相近种的形态异同点进行了比较分析。（3）基于小波分析和冗余度分析，发现颗粒直链藻的细胞形态参数（细胞直径和细胞长度）之间存在紧密关联，而细胞和藻链之间的关联性则较易被径流量引起的水体波动干扰。水温主要影响颗粒直链藻的出现率和尺寸的变化；径流量影响颗粒直链藻的生活周期及藻链长度的变化；营养盐主要影响一个生活周期的开始与结束。（4）颗粒直链藻形态特征的质量参数和数量参数的指示功能的对比分析发现，质量参数主要表现为空间模式。弯曲藻链所占百分比是空间分布的良好指示特征，因为其随着营养盐含量的增加而递增。而具末端分裂刺的藻链所占百分比是季节变化的良好指示特征。虽然数量参数呈现出清晰的时间模式，但是其中的任何单一参数都无法作为空间或时间的指示特征。质量参数和数量参数之间的关联性反映出了链状硅藻对外部环境的内在适应机制。基于以上研究，获得研究成果9项，包括7篇学术论文和2项专利。其中第一作者发表SCI论文4篇，第一或通讯作者发表中文核心C库论文3篇。申报专利2项，其中1项为国家PCT专利，已完成国际检索报告；另一项为国内发明专利，已进入一通答辩阶段，目前已完成对审查意见的申诉内容。