青海湖1.8万年以来甲藻Dinoflagellate群落变化及其古气候环境的指示意义

Ancient DNA Derived from Dinoflagellates in Qinghai Lake Sediments and their Implications for Paleoclimate and Paleoenvironment Constructions 

中文关键词:  青海湖  沉积物  古DNA  Dinoflagellate藻 18S rRNA基因  古气候环境变化

英文关键词:Qinghai Lake  Sediment  Ancient DNA  Dinoflagellate 18S rRNA gene  qPCR  Paleo-climate and-environment variations

中文摘要:

      近年来,有学者通过古DNA方法成功地重建了海洋沉积记录中古微生物群落变化,并借此反演了当地古环境—气候变化。然而,此种方法对于陆地湖泊沉积记录是否适用仍然有待研究。采用聚合酶链式反应(PCR, Polymerase Chain Reaction)、变性梯度凝胶电泳(DGGE,Denaturing Gradient Gel Electrophoresis)与实时荧光定量聚合酶链式反应(Q-PCR,Quantitative PCR)相结合的综合分析技术手段,系统研究青海湖5.8 m(时间跨度为~18 500 a)沉积柱中的甲藻(Dinoflagellate)多样性和丰度变化。研究结果显示,青海湖Dinoflagellate藻18S rRNA基因序列主要与海洋型藻类Woloszynskiahalophila和Scrippsiellahangoei相近(~98%序列相似性)。定量Q-PCR结果显示,每克沉积物含有dinoflagellate藻类18S rRNA基因丰度范围为2.27×10³~8.55×10⁶拷贝。另外,Dinoflagellate藻类18S rRNA基因丰度与总有机碳含量成显著正相关(R=0.408,p=0.0001)。对比分析揭示,较高的藻类丰度对应高总有机碳含量和较低的可溶解性盐电导率；反之,较低的藻类丰度对应较高的可溶解性盐电导率和较低的总有机碳含量。在青海湖区,总有机碳指示着季风降雨变化,并间接地指示着外源输入和湖泊营养状况变化,然而可溶性盐电导率则指示着湖泊盐度变化。综上所述,青海湖沉积柱Dinoflagellate藻类丰度可能反应了历史时期湖泊营养状况和盐度波动情况。

英文摘要:

      :In recent years, ancient DNA-basedmicrobial communities were retrieved from marine sedimentaryrecords, which were successfully applied to reconstruct local paleo-environmental changes. However, it is poorly known whether ancient DNA-basedmicrobial studies could be possible for reconstructing historic limnic environmental conditionsin lacustrine sedimentary records. Here, we investigatedthe diversity and abundance of light-dependent dinoflagellate algaein a 5.8 m sediment core(spanning the last 18,0 years) of Qinghai Lake using an integrated approach including polymerase chain reaction (PCR), denaturing gradient gel electrophoresis(DGGE), and quantitative PCR(qPCR).Our phylogenetic results showed that the dinoflagellate 18S rRNA gene sequences from this study were closely (~98% identity) related to marine algalspeciesWoloszynskiahalophila and Scrippsiellahangoei.qPCR results showed that the dinoflagellateabundance in the sedimentsalong the Qinghai Lake core was 2.27×10³~8.55×10⁶ copies per gram sediment, which wassignificantly (R=0.408,p=0.0001) correlated withtotal organic carbon (TOC) content.Parallel analyses revealed that lowdin of lagellate 18S rRNA gene abundance corresponded to low TOC and high conductivities of soluble salt, whereas high dinoflagellate gene abundance corresponded to high TOC and low conductivities of soluble salt. In the Qinghai Lake region, TOC can be served asan indicator of paleo-precipitation, which is related to historic nutrient input; while the conductivities of soluble salt indicated salinity fluctuation. Therefore, our data suggested that temporal variation of dinoflagellate 18S rRNA gene abundance preserved inthe Qinghai Lake sediments mightreflect the variations innutrient level and salinity sincethe latePleistocene in the Qinghai Lake region.