热带岛礁生态系统底栖甲藻的生物多样性及其生态适应策略研究-以西沙群岛为例

Benthic dinoflagellates are widely distributed in the benthic ecosystems in world's coasts and islands. They functioned a very important role in the marine benthic food chains. Harmful events associated with benthic dinoflagellates, have been reported frequently over the last decade. An obvious distribution pattern has been found is that the biodiversity and the biomass of the benthic dinoflagellates decreased from the tropic to temperate areas. The most abundance is distributed in the tropical islands ecosystem. So far benthic dinoflagellates have not been extensively investigated worldwide. The degree to which various environmental factors control the distribution pattern of the individual populations or whole community is largely unknown. The Xisha is a typical tropical islands ecosystem，which includs islands, reefs, sandbanks and lagoons. There are also with rich substrates for benthic dinoflagelles growth. We propose to study the biodiversity, temporal and spatial distribution, and acclimation strategy of the benthic dinoflagellates to environments in different ecosystems in the Xisha Islands. The objective for the project are to answer the following scientific questions. How many species are there in the area(biodiversity)? What are the major factors that affect the distribution and abundance of benthic dinoflagellates? How does different population adapt to different environments (acclimation strategy)? Through this study, we try to identify the mechanism that benthic dinoflagellates widely distributed in the tropic islands ecosystems.

由于海洋底栖甲藻中有毒种类比例较高，对人类健康和海洋生态系统危害较大，因而成为近10多年来国际研究热点。底栖甲藻的分布具有明显的区域特征，种类和数量从低纬度的热带到高纬度温带存在递减趋势，热带海域分布最为丰富，尤以热带岛礁生态系统分布最为广泛。迄今国际上大多研究都集中在对于单一生态类型（如海岛、泻湖等）的底栖甲藻种类多样性、有毒种类的毒性分析等方面，对于热带岛礁不同类型生态系统的比较研究欠缺。本研究选择我国西沙群岛这一具有非常独特的、涵盖多种不同生态类型的热带岛礁生态系统为代表，通过对西沙群岛不同生态类型（岛、礁、沙洲和泻湖等）的现场调查，分析底栖甲藻的生物多样性和时空分布特征；通过实验研究，厘清种类系统发育关系、毒性特征和生理生态适应机制。项目研究可以为揭示热带岛礁生态系统底栖甲藻的群落特征和生态分布规律，阐明底栖甲藻适应热带岛礁生态环境的生态策略及其适应机制提供重要理论依据。

本研究以我国典型海域西沙群岛及其周边海域为研究对象，以西沙的宣德群岛和永乐群岛为研究重点，于不同时期共4次进行潮下带采样，通过采集大型藻、死珊瑚、海草和沙石等基质，分离、纯化、培养获得底栖甲藻的纯培养株系，利用形态学和分子系统学对培养的藻株进行鉴定和系统发育分析，确定其在分类学上的地位；同时利用液相色谱质谱联用技术分析底栖甲藻的产毒特征。通过研究，主要结果如下：.1） 在西沙群岛及其邻近海域共鉴定出17种底栖甲藻，隶属于Prorocentrum，Gambierdiscus，Ostreopsis Coolia及Amphidinium 5个属，其中P. elegans，P. borbonicum，A. theoderi和G. sp. type 5等4个种为中国的新记录种，另外13个种分别是P. lima，P. rhathymum，P. concavum，P. cf. emarginatum，P. caipirignum，A. operculatum，A. gibbosum，G. pacificus，G. silvae，G. caribaeus，C. tropicalis，O. cf. ovata和O. lenticularis。.2）对西沙海域的甲藻毒素和毒性分析发现，采自西沙群岛的所有利马原甲藻都含有毒素。P. lima和P. caipirignum藻株产生OA，含量变化407 –3816 fg cell-1；P. lima还同时产生DTX-1，浓度变化74 –184 fg cell-1。首次报道了西沙两株P. lima藻株能产生DTX-2毒素。G. pacificus产生CTX2和CTX3，浓度变化分别为0.0249 –0.0262和0.0272 –0.0384 pg cell-1。热带库里亚藻对卤虫幼体表现了毒性效应，不同株系半致死浓度（LC50）为1.42 –1.92 mg mL-1。.3）温度实验发现西沙群岛的底栖甲藻种类O. cf. ovata、O. lenticularis和G. caribaeus具有广温性，适应较广的温度范围（15 –35℃）。O. cf. ovata、O. lenticularis和G. caribaeus三种底栖甲藻的最适生长温度分别为30、25、20-35 ℃。.4）发表学术论文9篇，其中SCI收录论文6篇；培养博士生1名