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Archaeal and bacterial glycerol dialkyl glycerol tetraethers (GDGTs) are globally abundant in soils under various climatic conditions, but little is known about their sources, relative distribution, and environmental controls on their diversity in high latitude permafrost deposits. Thus, constraints on GDGT-based proxies, such as methylation of branched GDGTs (MBT) or cyclization of branched GDGTs (CBT) used to infer mean annual temperature or soil pH, are also sparse. We investigated the GDGT diversity in typical North Siberian permafrost deposits including the active layer of polygonal tundra soils (seasonally frozen ground), fluvial terrace/floodplain sediments, Holocene and Pleistocene thermokarst sediments, and late Pleistocene Ice Complex (Yedoma). Our data show that isoprenoid GDGTs are produced by both methanotrophic and methanogenic Euryarchaeota, as well as Thaumarchaeota, but their abundance does not seem to be controlled by the investigated physicochemical parameters including %TOC, %TN, and soil pH. Branched GDGTs (brGDGTs) show similar distributional changes to those observed in other high latitude soil samples, i.e., a dominance of pentamethylated and hexamethylated brGDGTs, likely reflecting the adaptation to low temperatures and a positive correlation of the degree of cyclization with soil pH. Specifically, brGDGT-IIIa correlates positively with %TOC and %TN and negatively with soil pH, while brGDGT-Ib and brGDGT-IIb correlate negatively with %TOC and %TN and positively with pH. Moreover, we observe a negative correlation between 5-methyl and 6-methyl brGDGTs without cyclopentane moieties (except brGDGT-IIIa), but this anticorrelation does not seem to be related to the investigated physicochemical parameters. The observed brGDGT distribution yields a permafrost-specific soil pH calibration, pH0 PF ¼ 1:8451 � CBT0 PF þ 8:5396 (r2 = 0.60, RMSE = 0.074; n = 109). The different investigated deposit types show some distinct GDGT distributional changes an

In this study, we use a combined biomarker and macrofossil approach to reconstruct the Holocene climate history recorded in Trifna SO, Skallingen area, eastern North Greenland. Chronological information is derived from comparison of lithological, biogeochemical and macrofossil characteristics with a well-dated record from nearby Lille Sneha SO. Following local deglaciation around c.8cal.kaBP, the local peak warmth occurred between c.7.4 and 6.2cal.kaBP as indicated by maximum macrofossil abundances of warmth-demanding plants (Salix arctica andDryas integrifolia) and invertebrates (Daphnia pulex and Chironomidae). Warm conditions were dominated by terrestrial organic matter (OM) sedimentation as implied by the alkane-based P-aq ratio, but increased aquatic productivity is indicated when temperature was highest around 6.5cal.kaBP. The n-C-29/n-C-31 alkane ratio shows that vegetation in the catchment was dominated by shrubs after deglaciation, but shifted towards relatively more grassy/herbaceous vegetation during peak warmth. After 5.4cal.kaBP, the disappearance of warmth-demanding plant and invertebrate macrofossils indicates cooling in the Skallingen area. This cooling was characterized by a significant shift towards dominance of aquatic OM sedimentation in Trifna SO as implied by high P-aq ratios. Cooling was also associated with a shift in vegetation type from dwarf-shrub heaths towards relatively more herbaceous vegetation in the catchment, stronger erosion and more oligotrophic conditions in the lake. Our data show that mean air temperatures inferred using branched glycerol dialkyl glycerol tetraethers (brGDGTs) do not seem to accurately reflect the local climatic history. Irrespective of calibration, methylation of branched tetraethers (MBT) palaeothermometry cannot be reconciled with the macrofossil evidence and seems to be biased by either changing brGDGT sources (insitu vs. soil-derived) or changing species assemblages and/or an unknown physiological respons

Atmospheric circulation over the North Atlantic has undergone significant fluctuations during the Holocene. To better constrain these changes and their impacts on the Fennoscandian subarctic, we investigated molecular and inorganic proxies as well as plant wax D/H isotopes (D-C28) in a Holocene sedimentary record from Lake Tornetrask (Sweden). These data indicate a thermal maximum c. 8100 to 6300cal. a BP with reduced soil organic matter input, followed by a long-term cooling trend with increasing soil erosion. D data suggest a stable atmospheric circulation with predominance of westerly flow and North Atlantic moisture sourcing during the Early and Middle Holocene. Asubstantial depletion in D followed by increased flood frequency starting at c. 5300cal. a BP and intensifying c. 1500cal. a BP suggests a reorganization of the atmospheric circulation from zonal towards meridional flow with predominantly Arctic Ocean and Baltic Sea moisture sourcing.

The Atacama Desert is considered one of the driest places on Earth, where the availability of water plays a crucial role in determining the presence of plants. The sparse vegetation is limited to the coastal mountains, where abundant fog provides the main source of water and nutrients for unique Tillandsia landbeckii ecosystems. The apparent retreat of this fog-dependent vegetation over the past decades, however, may relate to changing climatic conditions, in particular increasing aridity. In this study, we used the nitrogen isotopic composition (delta N-15) of plant organic matter as a measure of water availability and atmospheric nitrogen input in present and past Tillandsia dune fields. We compiled an extensive data set on delta N-15 values of living plants and corresponding site factors (latitude, elevation, cloud cover and precipitation) along a coastal transect We present radiocarbon-based ages of relict T. landbeckii layers preserved in sand dunes that evolved episodically over the past 2500 years. Site-averaged delta N-15 values range from +2 parts per thousand to -16 parts per thousand, with variations of up to 4 parts per thousand observed within one site that can be related to changes in elevation. The spread in delta N-15 values is surprising and considerably larger than previously reported for T. landbeckii. In contrast, delta N-15 values of Huldobria fruticosa and Ophryosporus spp. leaves collected mostly below and above the fog zone vary between +4 parts per thousand and + 17 parts per thousand, largely in agreement with global observations from water-limited systems. Comparison with satellite-based meteorological data and modelling results revealed significant correlations between delta N-15 values of T. landbeckii and total cloud cover (r = - 0.90; p < .01), cloud height (r = -0.93; p < .001) and precipitation (r = -0.98; p < .001) along the investigated transect. The gradient in delta N-15 values further coincides with surface ocean nutrient concen

We investigated the origin of sedimentary bacteriohopanepolyols (BHPs) in low-density (<1.6 g cm(-3)), mesodensity (1.6-2.0 and 2.0-2.5 g cm(-3)) and high-density fractions (>2.5 g cm(-3)) as well as unfractionated bulk samples in a highly dynamic coastal setting along a transect spanning from the Mississippi Delta into the Gulf of Mexico (GOM). We observe selective partitioning of BHPs among density fractions both in total abundance and structural diversity. BHPs primarily accumulate in the low-density fraction at all sites. Good correlation with other particle properties [surface area-normalized organic carbon loadings (OC/SA), C/N ratios, Delta C-14 values, and lignin phenol abundances] and the spatial distribution of absolute and relative BHP abundances suggests that a significant fraction of BHPs are terrestrially sourced and entrained in the OC pool that is stabilized on clay particles or associated with plant fragments. Only a small subset of BHPs seems to have a significant autochthonous origin at the station furthest offshore and they are associated with the low and mesodensity fractions. While provenance and hydrodynamic sorting of particles across the shelf seem to primarily determine BHP inventories along the transect, the samples also harbor an unusual diversity of amino-functionalized BHPs. A subset of these BHPs appears to derive from aerobic methane oxidizing bacteria and are likely exported with particles from the coastal swamps in the Mississippi Delta. Other amino-functionalized BHPs seem to derive from aerobic ammonia oxidizing bacteria thriving in the nutrient-rich Mississippi River plume. We find no evidence for anaerobic ammonium oxidizing bacteria related to recurring seasonal hypoxia on the Louisiana Shelf.

Authentic biomarker standards were obtained from algal cultures in an attempt to accurately determine blank C added during sample processing for compound-specific radiocarbon analysis. Emiliania huxleyi and Thalassiosira pseudonana were grown under manipulated Delta C- 14 dissolved inorganic carbon (DIC) levels and chlorophyll a and either alkenones (E. huxleyi) or low molecular weight (LMW) alkanoic acids (T pseudonana) were isolated from the respective biomass using preparative liquid chromatography (LC), wet chemical techniques or preparative gas chromatography, respectively. (DIC)-C- 14 in the seawater medium was determined pre- and post-growth. Biomarker Delta C- 14 values mostly agree within 1 sigma or 2 sigma analytical uncertainties. In those cases where biomarker Delta C- 14 values differ significantly, chlorophyll a is up to 104% more C-14-depleted than alkenones or LMW alkanoic acids, consistent with a larger LC blank compared to the other purification methods. However, in the majority of experimental setups pre- and post-growth DIC Delta C-14 values seem to be compromised by an unknown and variable blank C contribution. DIC Delta C-14 values deviate strongly from the anticipated Delta C- 14 values (by up to ca. 560 parts per thousand, pre- and post-growth Delta C- 14 values differ significantly (by up to ca. 460 parts per thousand, and changes are not unidirectional. Accordingly, since the substrate Delta C- 14 value cannot unequivocally be constrained, blank C contributions for the different biomarker purification methods cannot be accurately calculated. This study illustrates the challenges and problems of producing authentic standards that are not readily commercially available and exemplifies how a laborious and time-consuming culturing approach may enter a vicious cycle of blank C contamination hampering accurate blank C determination.

We present a novel method to measure the C-13/C-12 isotope ratio (reported as delta C-13) of individual, intact bacteriohopanepolyols (BHPs) using semi-preparative ultrahigh pressure liquid chromatography (UPLC) followed by high temperature gas chromatography-isotope ratio mass spectrometry (HT-GC-IRMS). The method is reproducible, as indicated by the precision of delta C-13 values for bacteriohopanetetrol (BHT) extracted from R. palustris biomass and analyzed across an order-of-magnitude range of IRMS peak areas (delta C-13 = -33.4 +/- 0.6 parts per thousand VPDB, n = 94, +/- 1 sigma). To show that this method successfully separates individual BHPs from complex environmental matrices, we report delta C-13 values for BHT and the BHT stereoisomer (BHT-II) from a ca. 2.9 Ma, organic-rich Mediterranean Sea sediment sample. These analyses suggest that intact BHP delta C-13 measurements can greatly improve the interpretation of environmental signals by alleviating the need for side-chain cleavage which reduces BHP source-specificity. (C) 2018 Elsevier Ltd. All rights reserved.

Bacteriohopanepolyols (BHPs) are characterized by a large structural diversity, although methodological constraints have limited investigations of the occurrence of isomers among composite BHPs in environmental samples. Here, we describe a novel chromatography method that uses three serial Phenomenex Kinetex C-18 columns to successfully resolve new structural isomers of BHPs commonly observed in marine sediment samples. The investigated samples consistently contain a high diversity of BHP isomers, but their relative abundances differ significantly between samples. These differences in relative abundance have potential to reflect different environmental conditions such as depositional setting or redox conditions. The improved BHP resolution and baseline separation of the new method is promising for accurate quantification and future environmental proxy development and compound-specific isotope work. (C) 2018 Elsevier Ltd. All rights reserved.

In this study, we present lipid biomarker and palynological data for a sediment core from Lake Dojran (Macedonia/Greece), which covers the entire Holocene period. We analyzed vascular plant-derived n-alkanes, combustion-derived polycyclic aromatic hydrocarbons (PAHs), fecal steroids, and bacterial and archaeal glycerol dialkyl glycerol tetraether (GDGT) lipids in concert with microcharcoal and pollen assemblages to reconstruct climatic, environmental, and human impact in the Dojran catchment and the greater Dojran area. Overall, our results suggest a relationship between anthropogenic activity and environmental/climatic change since increased human impact corresponds to phases of higher humidity and high lake levels at Lake Dojran. During the early Holocene, the record reveals increasing temperatures and humidity and concurrent increasing vegetation cover and runoff/soil erosion, respectively. Following a thermal maximum during the middle early Holocene, temperatures decrease gradually until present. The middle-Holocene at Lake Dojran is characterized by relatively stable environmental conditions followed by greater climatic instability and strong anthropogenic overprint during the late-Holocene. The fecal stanol record reveals phases of increased human impact during the early Bronze Age, the late Bonze/early Iron Age, and the Middle Ages. A phase of low stanol and PAH concentrations from the late Iron Age until the early Middle Ages is either related to ecosystem changes and/or changes in settlement pattern since concurrent pollen data indicate intensified land use. Human impact re-intensified during the Middle Ages with some variability probably related to climatic variations of the Medieval Warm Period' and the Little Ice Age'.

Understanding the preservation and deposition history of organic molecules is crucial for the understanding of paleoenvironmental information contained in their abundance ratios such as Uk’37 and TEX86 used as proxies for sea surface temperature (SST). Based on their relatively high refractivity, alkenones and glycerol dialkyl glycerol tetraethers (GDGTs) can survive postdepositional processes like lateral transport, potentially causing inferred SSTs to be misleading. Likewise, selective preservation of alkenones and GDGTs may cause biases of the SST proxies themselves and can lead to decoupling of both proxy records. Here we report compound-specific radiocarbon data of marine biomarkers including alkenones, GDGTs, and low molecular weight (LMW) n-fatty acids from Black Sea sediments deposited under different redox regimes to evaluate the potentially differential preservation of both biomarker classes and its effect on the SST indices Uk’37 and TEX86. The decadal Δ14C values of alkenones, GDGTs, and LMW n-fatty acids indicate similar preservation under oxic, suboxic, and anoxic redox regimes and no contribution of pre-aged compounds, e.g., by lateral supply. Moreover, similar 14C concentrations of crenarchaeol, alkenones, and LMW n-fatty acids imply that the thaumarchaeotal GDGTs preserved in these sediments are produced in the euphotic zone rather than in subsurface/thermocline waters. However, we observe biomarker-based SSTs that strongly deviate (ΔSST up to 8.4°C) from in situ measured mean annual SSTs in the Black Sea. This is not due to redox-dependent differential biomarker preservation as implied by their Δ14C values and spatial SST pattern. Since contributions from different sources can largely be excluded, the deviation of the Uk’37 and TEX86 proxy-derived SSTs from in situ SSTs requires further study of phylogenetic and other yet unknown environmental controls on alkenone and GDGT lipid distributions in the Black Sea.

Thaumarchaeota, the major sources of marine glycerol dibiphytanyl glycerol tetraether lipids (GDGTs), are believed to fix the majority of their carbon directly from dissolved inorganic carbon (DIC). The delta C-13 values of GDGTs (delta C-13(GDGT)) may be powerful tools for reconstructing variations in the ocean carbon cycle, including paleoproductivity and water mass circulation, if they can be related to values of delta C-13(DIC). To date, isotope measurements primarily are made on the C-40 biphytane skeletons of GDGTs, rather than on complete tetraether structures. This approach erases information revealed by the isotopic heterogeneity of GDGTs within a sample and may impart an isotopic fractionation associated with the ether cleavage. To circumvent these issues, we present delta C-13 values for GDGTs from twelve recent sediments representing ten continental margin locations. Samples are purified by orthogonal dimensions of HPLC, followed by measurement of delta C-13 values by Spooling Wire Microcombustion (SWiM)-isotope ratio mass spectrometry (IRMS) with 1 sigma precision and accuracy of +/- 0.25%. Using this approach, we confirm that GDGTs, generally around -19%, are isotopically heavy compared to other marine lipids. However, measured delta C-13(GDGT) values are inconsistent with predicted values based on the C-13 content of DIC in the overlying water column and the previously-published biosynthetic isotope fractionation for a pure culture of an autotrophic marine thaumarchaeon. In some sediments, the isotopic composition of individual GDGTs differs, indicating multiple source inputs. The data appear to confirm that crenarchaeol primarily is a biomarker for Thaumarchaeota, but its delta C-13 values still cannot be explained solely by autotrophic carbon fixation. Overall the complexity of the results suggests that both organic carbon assimilation (ca. 25% of total carbon) and multiple source(s) of exogenous GDGTs (contributing generally <30% of input to sedime

Understanding the preservation and deposition history of organic molecules is crucial for the understanding of paleoenvironmental information contained in their abundance ratios such as U-37(k') and TEX86 used as proxies for sea surface temperature (SST). Based on their relatively high refractivity, alkenones and glycerol dialkyl glycerol tetraethers (GDGTs) can survive postdepositional processes like lateral transport, potentially causing inferred SSTs to be misleading. Likewise, selective preservation of alkenones and GDGTs may cause biases of the SST proxies themselves and can lead to decoupling of both proxy records. Here we report compound-specific radiocarbon data of marine biomarkers including alkenones, GDGTs, and low molecular weight (LMW) n-fatty acids from Black Sea sediments deposited under different redox regimes to evaluate the potentially differential preservation of both biomarker classes and its effect on the SST indices U-37(k') and TEX86. The decadal Delta C-14 values of alkenones, GDGTs, and LMW n-fatty acids indicate similar preservation under oxic, suboxic, and anoxic redox regimes and no contribution of pre-aged compounds, e.g., by lateral supply. Moreover, similar C-14 concentrations of crenarchaeol, alkenones, and LMW n-fatty acids imply that the thaumarchaeotal GDGTs preserved in these sediments are produced in the euphotic zone rather than in subsurface/thermocline waters. However, we observe biomarker-based SSTs that strongly deviate (Delta SST up to 8.4 degrees C) from in situ measured mean annual SSTs in the Black Sea. This is not due to redox-dependent differential biomarker preservation as implied by their Delta C-14 values and spatial SST pattern. Since contributions from different sources can largely be excluded, the deviation of the U-37(k') and TEX86 proxy-derived SSTs from in situ SSTs requires further study of phylogenetic and other yet unknown environmental controls on alkenone and GDGT lipid distributions in the Black Sea. (C)

Understanding long-term environmental dynamics is crucial to elucidate recent and predict future feedback processes of permafrost in a changing environment. Northeastern Siberia is a key site to study organic matter (OM) that has been formed during the Pleistocene. This OM contains information about past vegetation, environment, and organismic communities,thus, offering the potential to understand environmental change of Arctic Russia on glacial and interglacial timescales. We analyzed five permafrost cores from Bol’shoy Lyakhovsky Island and the Buor Khaya Peninsula to study the environmental history of Northeastern Siberia for the past 130 kyr (MIS1, MIS3, and MIS5e) using molecular and isotopic tools. We present a comprehensive biomarker data set including terrestrial vascular plant biomarkers such as n-alkanes, n-fatty acids, and lignin phenols. In addition, we analyzed bacterial and archaeal membrane lipids including branched and isoprenoid glycerol dialkyl glycerol tetraethers (brGDGTs and isoGDGTs) and bacteriohopanepolyols (BHPs) from which environmental properties including mean annual air temperatures (MAAT) and pH, and bacterial taxonomic information can be constrained. Initial results show that MAATs as determined using brGDGTs were on average higher during MIS3 than MIS1 on both Bol’shoy Lyakhovsky Island and the Buor Khaya Peninsula. Higher MAATs during MIS3 are accompanied by lower BIT indices (based on brGDGTs and isoGDGTs) indicating relatively higher in-situ archaeal production than during MIS1 when bacteria dominate and soil pH is lower. On Bol’shoy Lyakhovsky Island vascular plant-derived, high molecular weight (HMW) n-alkanes are also more abundant in the MIS1 deposits than the MIS3 deposits and co-vary with low pH and low MAAT while the opposite trend is observed for the Buor Khaya Peninsula deposits. HMW n-alkanes characteristic for Poaceae and Cyperaceae dominate the n-alkane assemblages during warm stages, while n-alkanes typical for the mos

Bacteriohopanepolyols (BHPs) are biomarkers providing taxonomically and environmentally diagnostic information. BHPs may help to unravel the composition of bacterial communities residing in recent as well as ancient permafrost soils and sediments and also provide information on associated environmental conditions. However, detailed data on their distribution in the heterogeneous Arctic environment are scarce. The distribution and structural diversity of BHPs were studied in the annually thawing (active) layer of three different sites in the polygonal tundra of the Lena Delta in the Siberian Arctic. Variations between permafrost structures and soil horizons caused by differences in the physical and chemical soil properties were observed. C and N content is significantly correlated with the BHP composition so that the highest BHP concentrations and greatest structural diversity occur in the upper most organic soilhorizons, which consist mainly of fresh or little degraded plant material. Furthermore, statistical analyses reveal that higher abundances of adenosylhopane-type soil marker BHPs are linked to higher soil pH values. Small scale environmental controls on BHP distributions are reflected by amine-functionalised BHPs from methanotrophic bacteria only occurring in the water-saturated, oxygen-depleted polygon centres and by soil marker BHPs, which are significantly more abundant in the well aerated polygon rims than in the centres. In contrast, C-2 methylated BHPs, putative indicators of plant-bacterial interactions, are present in all soil horizons and permafrost structures and their relative distribution is not systematically linked to soil properties. Overall, lipid-based results agree with published 16S rRNA based community structure assessments highlighting the usefulness of BHPs to represent bacterial populations in recent and ancient permafrost soils. (C) 2015 Elsevier Ltd. All rights reserved.

Bacteriohopanepolyols (BHPs) are biomarkers providing taxonomically and environmentally diagnostic information. BHPs may help to unravel the composition of bacterial communities residing in recent as well as ancient permafrost soils and sediments and also provide information on associated environmental conditions. However, detailed data on their distribution in the heterogeneous Arctic environment are scarce. The distribution and structural diversity of BHPs were studied in the annually thawing (active) layer of three different sites in the polygonal tundra of the Lena Delta in the Siberian Arctic. Variations between permafrost structures and soil horizons caused by differences in the physical and chemical soil propertieswere observed. C and N content is significantly correlated with the BHP composition so that the highest BHP concentrations andgreatest structuraldiversityoccur intheuppermost organic soilhorizons,whichconsistmainly of fresh or little degraded plant material. Furthermore, statistical analyses reveal that higher abundances of adenosylhopane-type soil marker BHPs are linked to higher soil pH values. Small scale environmental controls on BHP distributions are reflected by amine-functionalised BHPs from methanotrophic bacteria only occurring in the water-saturated, oxygen-depleted polygon centres and by soil marker BHPs, which are significantly more abundant in the well aerated polygon rims than in the centres. In contrast, C-2 methylated BHPs, putative indicators of plant-bacterial interactions, are present in all soil horizons and permafrost structures and their relative distribution is not systematically linked to soil properties. Overall, lipid-based results agreewith published 16S rRNA based community structure assessments highlighting the usefulness of BHPs to represent bacterial populations in recent and ancient permafrost soils.

Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Earth and Planetary Science Letters 290 (2010): 340-350, doi:10.1016/j.epsl.2009.12.030., Paired radiocarbon measurements on haptophyte biomarkers (alkenones) and on cooccurring tests of planktic foraminifera (Neogloboquadrina dutertrei and Globogerinoides sacculifer) from late glacial to Holocene sediments at core locations ME0005-24JC, Y69- 71P, and MC16 from the south-western and central Panama Basin indicate no significant addition of pre-aged alkenones by lateral advection. The strong temporal correspondence between alkenones, foraminifera and total organic carbon (TOC) also implies negligible contributions of aged terrigenous material. Considering controversial evidence for sediment redistribution in previous studies of these sites, our data imply that the laterally supplied material cannot stem from remobilization of substantially aged sediments. Transport, if any, requires syn-depositional nepheloid layer transport and redistribution of low-density or fine-grained components within decades of particle formation. Such rapid and local transport minimizes the potential for temporal decoupling of proxies residing in different grain size fractions and thus facilitates comparison of various proxies for paleoceanographic reconstructions in this study area. Anomalously old foraminiferal tests from a glacial depth interval of core Y69-71P may result from episodic spillover of fast bottom currents across the Carnegie Ridge transporting foraminiferal sands towards the north., This study was funded by the Helmholtz Young Investigators Group „Applications of molecular 14C analysis for the study of sedimentation processes and carbon cycling in marine sediments”. G.M. acknowledges financial support from WHOI postdoctoral scholarship program. T.I.E. was supported by NSF grant OCE-0526268. A.C.M. was supported by NSF grant ATM0602395.