热带富营养化湖泊中浮游植物的脂肪酸组成与分布

星湖位于广东省．是一个热带地区的湖泊．本文测定和分析了该湖的两个子湖仙女湖和中心湖浮游植物群落的脂肪酸组成,探讨了浮游植物群落特征与脂肪酸组成之间的关系．两个子湖的富营养化程度较高,其中中心湖更严重．仙女湖的浮游植物群落以蓝藻为主导,而在中心湖则蓝藻或金藻占优势．浮游植物样品中检测到的脂肪酸碳链长为16碳到22碳．其中饱和脂肪酸和单不饱和脂肪酸种类较少,均有3种;而高不饱和脂肪酸的种类相对较多．两个子湖的脂肪酸均以饱和脂肪酸为主,高不饱和脂肪酸浓度相对较低．对于单一的脂肪酸种类来说,C16：0浓度最高,其浓度与蓝藻数量有很高的相关性(R^2=0．955,P=0．001),表明样品中的C16：0主要来源于蓝藻．而富含EPA(二十碳五烯酸)的硅藻和隐藻生物量高时其浮游植物的EPA浓度也较高;在中心湖中高浓度的DHA(二十二碳六烯酸)主要来源于金藻总之．两个子湖泊的脂肪酸组成与浮游植物群落结构特征基本一致．

Composition and Distribution of Fatty Acids for Phytoplankton in a Typical Tropical Lake

Lake Xinghu is a typical eutrophic lake consisting of 6 sub-lakes in tropical Guangdong Province. We reported the fatty acid composition of phytoplankton community and the relationship between the fatty acids and phytoplankton in the two sub-lakes; Xiannu Lake and Zhongxin Lake in July, October and December of 2002. For the two sampled sub-lakes, Zhongxin Lake had a higher trophic level than the Xiannu Lake. In the former, Cyanophyceans were the dominant phytoplankton in July and October, but was replaced by Chrysophyceans in December. In the latter, Cyanophyceans predominated numericallyin all sampling periods. The carbon chains of the fatty acids for phytoplankton in the water samples ranged from 16 to 22. 3 species of saturated fatty acids, 3 monounsaturated fatty acids and 7 polyunsaturated fatty acids were detected. The saturated fatty acids dominated in the total fatty acids, the polyunsaturated fatty acids were low in the two sub-lakes. For single species of fatty acids, the concentration of C16:0 was the highest in all the fatty acids. It showed a significant relationship with the abundance of Cyanophyceans, which indicated that the C16:0 was rooted in the Cyanophyceans. The Bacillariopheans and Cryptophyceans were rich in EPA, and the concentration of EPA in phytoplankton was high with the biomass of the Bacillariopheans and Cryptophyceans. The high concentration of DHA was observed in Zhongxin Lake in the December, which should be primarilyfrom Chrysophyceans. Generally speaking, the composition of the fatty acids in the water samples was consistentwith the structures of phytoplankton community.