A new approach to detecting vegetation and land-use change using high-resolution lipid biomarker records in stalagmites

A hundred-year stalagmite lipid biomarker record from Mechara, southeastern Ethiopia, is presented. The record has been recovered at a 10-yr temporal resolution, marking the first time this has been achieved in stalagmite biomarker work and providing the first opportunity to investigate the relationship between stalagmite lipid records and hydrological transport lags, a vital issue in interpreting palaeoenvironmental signals. Preserved plant-derived n-alkanes and n-alkanols show clear changes in composition over time, relating to known land-use changes in the area, particularly the expansion of agriculture in the early twentieth century. The level of environmental detail provided by this technique, combined with the long-term chronological framework offered by stalagmites, holds significant promise for the investigation of early human environments and their associated climatic and anthropogenic controls.     

Late Holocene sea-surface temperature and precipitation variability in northern Patagonia, Chile (Jacaf Fjord, 44°S)

A high-resolution multi-proxy study including the elemental and isotopic composition of bulk organic matter, land plant-derived biomarkers, and alkenone-based sea-surface temperature (SST) from a marine sedimentary record obtained from the Jacaf Fjord in northern Chilean Patagonia (44°20′S) provided a detailed reconstruction of continental runoff, precipitation, and summer SST spanning the last 1750 yr. We observed two different regimes of climate variability in our record: a relatively dry/warm period before 900 cal yr BP (lower runoff and average SST 1°C warmer than present day) and a wet/cold period after 750 cal yr BP (higher runoff and average SST 1°C colder than present day). Relatively colder SSTs were found during 750–600 and 450–250 cal yr BP, where the latter period roughly corresponds to the interval defined for the Little Ice Age (LIA). Similar climatic swings have been observed previously in continental and marine archives of the last two millennia from central and southern Chile, suggesting a strong latitudinal sensitivity to changes in the Southern Westerly Winds, the main source of precipitation in southern Chile, and validating the regional nature of the LIA. Our results reveal the importance of the Chilean fjord system for recording climate changes of regional and global significance.     

An Overview of the Applications of Lipid Carbon Isotope Compositions in the Paleoenvironmental and Paleoecological Reconstructions in Lacustrine and Peat Deposits

Lipids preserved in geological materials mainly originate from cell membrane and leaf waxes, and have the potential to infer biological sources, metabolic pathways, and environmental information. Thus,lipid-based proxies have been widely applied to reconstruct paleoenvironment and paleoecology in the Quaternary. Except the concentration and molecular composition, the carbon isotope compositions of lipids are also a type of important signal sources. For photoautotrophs, the carbon isotope compositions of lipids are mainly mediated by the carbon isotope discrimination during the photosynthesis and lipid biosynthesis processes. In contrast, the carbon isotope compositions of heterotroph derived lipids are controlled by substrates and the carbon isotope fractionation during biosynthesis. In this review, we overview the advances of applications of lipid carbon isotope ratios in lacustrine and peat deposits. In the near future, more attention is suggested to pay to instrumental techniques, such as reduce the sample amount, direct analysis the carbon isotope compositions of molecules with relatively large molecular weight (e.g. BHPs, GDGTs), and widely application of compound-specific radiocarbon isotope analysis. In addition, combination of carbon isotope ratios from multi lipids, or the application of dual carbon and hydrogen isotope ratios of lipids, will shed more information on the response of ecological processes to climate changes. Furthermore, more works are worthy to investigate the relation between biogeochemical processes and paleoclimate changes in the Quaternary.     

矿业废弃地先锋植物盐生草在镍、铜处理下抗氧化酶系统的变化

采用温室盆栽法,研究镍(Ni)、铜(Cu)单一处理（0、50、100、200、400 mg·kg-1）对金昌Ni/Cu尾矿库先锋植物盐生草(Halogeton glomeratus)幼苗Ni、Cu积累、膜脂过氧化程度与抗氧化酶系统的影响。结果表明：盐生草幼苗叶片及根部Ni、Cu含量随土壤中Ni、Cu含量的增加而增加,Ni、Cu含量以根部含量为高;叶片及根部丙二醛(MDA)含量随Ni、Cu处理浓度升高显著增加,膜脂过氧化程度加剧;Ni胁迫下盐生草叶片中仅抗坏血酸酶(APX)活性随Ni浓度增加总体呈增加趋势,在对抗Ni胁迫引起的氧化胁迫方面发挥着主要作用,根部超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)、APX和谷胱甘肽还原酶(GR)活性随Ni浓度增加呈上升趋势,在减轻Ni胁迫引起的氧化损伤方面起着重要作用;Cu胁迫下盐生草叶片SOD和APX活性较对照有所增强,在减弱Cu胁迫引起的氧化损伤方面发挥着一定作用,根部上述5种抗氧化酶活性随Cu浓度增加总体呈增加趋势,在缓解Cu胁迫引起的氧化损伤方面发挥着重要作用。     

Organic matter source and thermal maturity within the Late Cretaceous Niobrara Formation,U.S. Western Interior

The Late Cretaceous sedimentary record of the North American Western Interior Seaway is characterized by cyclic deposition of organic carbon-rich sediments. One notable interval during the late Coniacian-Santonian is recorded by the Niobrara Formation. The organic carbon-rich interval within the Niobrara Formation has been identified as Oceanic Anoxic Event (OAE) 3. Understanding the reason for this distribution of organic carbon within the Niobrara Formation requires a refined understanding of the source and maturity of the organic matter. In this study, we present lipid biomarker records from the USGS Portland #1 core (Cañon City, CO) to constrain the thermal maturity of the organic matter and the differing contributions of organic matter sources. Sterane and hopane thermal maturity indices indicate that the samples are somewhat immature with respect to oil formation and that there is strong agreement between different proxies for thermal maturity. Based on the distribution of n-alkanes, steranes, and hopanes, there is a significant increase in the contribution of algal organic matter during and after OAE 3, coeval with increased organic carbon accumulation. Although a consistent terrestrial contribution is observed, it is only a minor source of organic matter at the Portland core location and does not drive increased organic matter accumulation during OAE 3. Of particular note is the consistent influence of even-over-odd predominantly mid-chain length (C₂₁ to C₂₅) organic matter. This observation within the brackish to marine, not methanogenic WIS represents an expansion of the depositional settings in which even-over-odd predominance has been observed in mid-chain length n-alkanes. Pristane (Pr) and phytane (Ph) abundances are inconsistent with a redox control on Pr/Ph ratios and suggest an increase in the delivery and/or preservation of phototrophic organic matter as the source for pristane and phytane in the Portland core.