微生物醚类化合物在泥炭古环境重建中的应用:进展与问题

Application of Microbial Ether Lipids in the Reconstruction of Paleoenvironments in Peatlands:Progress and Problems

泥炭是研究古环境的良好载体,也是陆地重要的有机碳库。泥炭中微生物醚类化合物结构多样、含量丰富、生物来源较为明确,其分布主要受温度、pH和氧化还原状况的影响,可以作为古环境重建的代用指标,也是甲烷循环等生物地球化学过程的示踪计。一些微生物醚类如GMGTs、isoGDGTs异构体和BDGTs的含量可能被开发为泥炭新的古环境和产甲烷作用指标。当前,醚类在泥炭古环境重建和产甲烷作用重建中还存在一些问题,包括pH指标与有效降水量之间的关系不明确,沉积相转变对泥炭古环境重建和产甲烷活动重建可能存在影响,brGDGTs重建温度存在不确定性,需要进一步研究。

Peat is a good archive for paleoenvironment reconstruction and an important terrestrial organic carbon sink.Microbial ether lipids in peatlands are structurally diverse and rich in abundance,and most of these lipids have been thought to be derived from specific biological sources.Their distributions are mainly controlled by temperature,pH and redox conditions,etc.They can be used as proxies for the reconstruction of paleoenvironments,such as temperature,water table and redox conditions and also as tracers of biogeochemical processes,e.g.,methane cycling.Microbial ether lipids identified in peatlands can be divided into seven groups:archaeol and OH-archaeol,isoGDGTs and OH-isoGDGTs,brGDGTs,BDGTs and PDGTs,isoGMGTs and brGMGTs,Me-isoGDGTs and Me-isoGMGTs,and GDDs.Here we introduced the structures,biological sources of these ether lipids,and environmental factors influencing their distributions in global peatlands.We showed how microbial ether lipid-based proxies for the reconstruction of the peat paleoenvironment were developed and discussed their advantages and disadvantages.We also discussed the application of microbial ether lipids in indicating methane cycling in peatlands.The abundance of some microbial ether lipids such as GMGTs,isoGDGT isomers and BDGTs can be developed as new proxies for the reconstruction of the paleoenvironment(paleotemperature,paleo-pH,paleohydrology)and methanogenesis in peatlands.At present,some problems may still exist in the application of microbial ether lipids to the reconstruction of peat paleoenvironment and methanogenesis,including the unclear relationships of pH proxies and effective precipitation,the impact of sedimentary facies on the brGDGT-based reconstructions,the uncertainty of brGDGT-based proxies,and the influence of insoluble ether lipids.This highlight further research is needed to resolve these issues.In addition,several aspects need to be paid attention to in future studies,including further determining factors influencing microbial ether lipids in peatlands,understanding the role of methanogenesis in boreal peatlands in regulating the atmospheric CH4 concentration,and introducing some new technologies.