近200a来泸沽湖沉积物色素记录与区域气候变化的关系

Relationship between the sediment pigment records of Lake Lugu and the regional climate change over the last 200a

近百年来云贵高原区域气候变暖明显.为探讨湖泊生态系统变化与气候变化的关系,本文采集泸沽湖沉积物柱,分析测定了近200 a来沉积物柱芯中叶绿素及其衍生物(CD)、总胡萝卜素(TC)、颤藻黄素(Osc)和蓝藻叶黄素(Myx)4类色素及烧失量(LOI550℃)、生物硅、C/N值等指标,并与1951-2010年丽江地区气温和降雨量资料进行相关性分析.结果表明,以上4种色素含量及其比值(CD/TC,Osc/Myx)对区域气温变化较为敏感;近60 a来CD、TC、Osc、Myx、LOI550℃和生物硅含量与年均气温呈显著正相关;而CD、TC、Osc、Myx和C/N仅与5 a滑动年均降雨量呈正相关,表明气温可能是驱动泸沽湖初级生产力升高的主要因素之一,降雨量为次要因素.1990年后4种色素和有机质含量明显增加,C/N值呈下降趋势,湖泊初级生产力增强,内源有机质在沉积物总有机质中的比重增高.此外,Osc和Myx含量及其比值升高,反映蓝藻类生产力增长,颤藻类比重呈增大趋势,表明近20 a来在气温为主导因素的影响下不仅泸沽湖初级生产力增加,初级生产者群落组成也发生了变化.

A great number of palaeoclimatic proxies and modem instrumental data have indicated that the climate of Yunnan- Guizhou Plateau has undergone a significant warming during the past hundred years. In this study to reveal the impact of the region climate change on lake ecosystems, physical and chemical proxies in sediment core from the Lake Lugu were examined, including Loss-on-ignition at 550℃ （LOI550℃ ）, the concentrations of pigments, chlorophyll derivatives （CD）, total earotenoids （TC）, Oscillaxanthin （Ose） , Myxanthophyll （Myx） , biogenic silicon and C/N values. The correlations of those proxies with climate data of both temperature and precipitation from nearby Lijiang station during 195l--2010 AD were analyzed. The results showed that four pigment contents and two ratios CD/TC and Ose/Myx were sensitive to regional temperature changes. The CD, TC, Ose, Myx, LOI550℃ and biogenie silica content showed significantly positive correlations with average annual temperature in the last 60 years, while CD, TC, Osc, Myx and C/N had significantly positive correlations with the 5 years moving average precipitations. The result indicated that warming was possibly one of the main factors driving the increasing of primary productivity of the lake, while the effect of precipitation shows a secondary factor in the comparison. Since 1990, all the four pigments and LOI550℃ increased significantly while C/N ratios decreased, which indicated that the lake primary productivity were enhanced and its contribution to the total organic matter in sediments increased as well. The increasing of Osc and Myx contents and Ose/Myx ratio in the lake sediments reflected the increase of productivity of Cyanophyceae and the proportion of Oscillatoria in Cyanophyceae. The results indicated that the regional climate change over the last 20 years not only led to the increase of lake primary productivity, but also the change of composition of phytoplankton community, in Lake Lugu.