淡水超微型浮游植物多样性及其研究方法

A review of diversity of freshwater picophytoplankton and its related research methods

超微藻广泛分布于海洋和淡水生态系统中,在水生生态系统尤其是微食物环中起着重要作用。自20世纪70年代被发现以来,有关超微藻的研究大多集中在海洋,直到近年来淡水超微藻才受到广泛关注。目前淡水生境中发现的超微藻主要包括真核超微藻和原核聚球藻,而在海洋生境中分布广泛的原绿球藻在淡水环境中则很少被发现。超微真核藻多样性极其复杂,几乎在所有的门类都有发现;而目前在中国湖泊中发现的聚球藻主要以富含藻蓝素的聚球藻为主。影响超微藻生长的因子主要包括营养盐、温度、光照及生物因子(如捕食)等,自然水体的超微藻可能同时受多个以上环境因子的共同影响。由于超微藻细胞微小,形态特征不明显,而且大部分物种不能被分离纯培养,因此传统研究方法受到限制,直至近些年来,荧光显微技术、流式细胞术及分子生物学技术的发展,才使我们有机会对超微藻多样性和生态学有了进一步的认识。本文对淡水超微藻多样性的研究进展进行了综述,介绍了淡水超微藻的主要类群及其环境影响因子,重点阐述了当前超微藻的研究方法。

Picophytoplanktons are distributed worldwide and are ubiquitous in all types of oceans and lakes. They are a fundamental component of aquatic ecosystems,especially in the microbial loop. Previous researches were mainly focused on marine picophytoplankton since their discovery in the 1970 s,and only recently freshwater picophytoplankton has been received wide attention.Synechococcus and eukaryotic picophytoplankton are the main component of freshwater picophytoplankton discovered to date,while Prochlorococcus which is widespread in marine is rarely found in freshwater habitats. The eukaryotic component of picophytoplankton is of great diversity which comprises clusters from almost all algal phyla. However,Synechococcus found in lakes in China are mainly composed of phycocyanin-rich cells. The abiotic and biotic factors affecting their diversity include nutrients,temperature,light and predation,and picophytoplankton in natural waters could be affected by multiple factors at the same time. Traditional methods including microscopy observation and pure culture techniques hampered the progress of picophytoplankton study,due to its tiny cell size,insufficient distinct morphological features for taxonomic discrimination and being unculturable for most picophytoplankton species. Major advances in picophytoplankton ecology and taxonomy benefited from the introduction of new techniques,including epifluorescence microscopy,flow cytometry and molecular biology techniques. In this paper,we presented the species of freshwater picophytoplankton described to date,and discussed how they are affected by abiotic and biotic factors. In the end,we focused on the techniques recently used in picophytoplankton research.