晚更新世冰期以来渤海沉积层中古真菌多样性与群落演替研究

As an important group of microeukaryotes, fungi play non trivial roles as recyclers in biogeochemical cycles in numerous marine habitats. A few studies showed that the ancient fungi deposited deeply in marine sediment for several millennium or million years would play important roles in degradation of organic matter. However, information of ancient fungi in our country remains poorly understood, which is hindering our understanding of their succession history and ecological functions. From late Pleistocene to Holocene, sedimentary evidences suggested that the Bohai basin suffered at least three times of seawater intrusion and extinction events in cycle as a result of the periodic influence of glacial and interglacial periods. During preliminary research, we obtained 139 sediment samples from two drill holes of the 50m depth and 100m depth. The age of the sediment from the 100m depth hole was calculated as 160 thousand years ago, which is the time of occurrence of late Pleistocene. Therefore, using traditional cultural method and high-throughput sequencing, this study attempts to reveal the succession history of ancient fungal diversity and community in the Bohai basin from late Pleistocene. In addition, combined the data of global climate change, physicochemical property of sediment and plant pollen, we will try to discover how the alternate events of glacial and interglacial periods influence the succession of fungal diversity and community. This study will provide a significant contribution to the understanding of the resource, community succession and potentially ecological functions of ancient fungi buried in marine sediment.

真菌是一类重要的真核微生物，即使是深埋于海洋沉积层中几千年甚至几百万年的古真菌，仍在驱动地球碳氮化学循环过程中发挥重要作用。沉积地质学证据表明，在晚更新世至全新世之间，受冰期与间冰期的影响，渤海盆地至少经历了三次大规模海水入侵与消退事件，周期性的处于海相与陆相交替出现的古环境变迁中。前期申请人获得了渤海盆地50m深和100m深钻孔沉积层柱状样品，其中100m深处的沉积物测年数据显示为距今16万年前，正是晚更新世冰期发生的时间。鉴于此，本项目拟针对前期获得的柱状沉积层样品，结合传统培养方法和高通量测序技术，全面揭示晚更新世冰期以来渤海盆地沉积层中古真菌多样性与群落演替规律。同时，综合全球气候变化、沉积层理化性质、植物孢粉分析数据，尝试揭示冰期与间冰期所导致的渤海古环境变迁对真菌多样性与群落演替的影响。本研究所获得的数据可为认识我国古真菌资源、群落演替史及其潜在的生态功能提供重要参考。

晚更新世以来，受冰期与间冰期影响，全球气温出现暖期与冷期交替现象，导致海平面交替上升与下降。近五万年以来渤海海区发生过两次大的海侵与一次海退事件，其沉积物环境被学者划分为陆相、海相与滨海相。借助于渤海钻井平台地质勘探项目，课题组从渤海海盆的中西部区域获得了2个50m深钻孔和1个100m深钻孔不同深度的139份沉积层样品，AMS14C测年数据显示50m深度沉积层样品距今约有5万年历史。主要开展了以下研究工作：（1）基于全球气温与海平面变化数据、沉积层样品理化性质、测年数据等指标，分析了目标钻孔50m沉积层的沉积环境变化特点，即海相陆相交替出现的地质演变进程；（2）基于ITS2 rDNA扩增子高通量测序技术，分析了真菌多样性与群落结构随海相陆相交替出现的变化特点：501#钻孔沉积层中真菌OTUs丰富度与钻孔深度呈现显著的负相关关系，即随着钻孔深度增加OTUs丰富度逐渐降低。丰度前20的OTUs中，OTU_3450（Paraboeremia）、OTUs_11734（Phoma）与OTU_1196（Didymella）在陆相沉积层中发生量大于海相。沉积物理化指标TOC/TN与OTU_3450、OTU_11734发生量显著负相关。101#钻孔沉积层真菌群落结构明显不同于501#、502#钻孔，且沉积环境（海相、陆相、滨海相）对群落结构产生显著影响。（3）基于传统培养方法调查真菌多样性，共获得357株菌株，被鉴定为2门6纲7目9科12属21种。80%属于子囊菌门，20%属于担子菌门，其中散囊菌纲为优势纲，青霉属（Penicillium）菌株占55%，其次为曲霉属（Aspergillus）（4.9%）。担子菌门中红酵母属（Rhodotorula）是优势属（15.2%），其次为Vishniacozyma（1.2%）。本研究初步明确了晚更新世以来在海退、海进的地质演变历史进程中，渤海沉积层中古真菌多样性与群落组成的变化特点，为了解古微生物多样性及其对地质演变的响应提供参考。