Sinninghe Damste Jaap S.

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Sinninghe Damste
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Jaap S.
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  • Preprint
    Putative ammonia-oxidizing Crenarchaeota in suboxic waters of the Black Sea : a basin-wide ecological study using 16S ribosomal and functional genes and membrane lipids
    ( 2006-07-03) Coolen, Marco J. L. ; Abbas, Ben ; van Bleijswijk, Judith ; Hopmans, Ellen C. ; Kuypers, Marcel M. M. ; Wakeham, Stuart G. ; Sinninghe Damste, Jaap S.
    Within the upper 400 m at western, central, and eastern stations in the world’s largest stratified basin, the Black Sea, we studied the qualitative and quantitative distribution of putative nitrifying Archaea based on their genetic markers (16S rDNA, amoA encoding for the alfa-subunit of archaeal ammonia monooxygenase), and crenarchaeol, the specific glycerol diphytanyl glycerol tetraether (GDGT) of pelagic Crenarchaeota within the Group I.1a. Marine Crenarchaeota were the most abundant Archaea (up to 98% of the total archaeal 16S rDNA copies) in the suboxic layers with oxygen levels as low as 1 μM including layers where previously anammox bacteria were described (Kuypers et al., 2003). Different marine crenarchaeotal phylotypes (both 16S rDNA and amoA) were found at the upper part of the suboxic zone as compared to the base of the suboxic zone and the upper 15-30 m of the anoxic waters with prevailing sulfide concentrations of up to 30 μM. Crenarchaeol concentrations were higher in the sulfidic chemocline as compared to the suboxic zone. These results indicate an abundance of putative nitrifying Archaea at very low oxygen levels within the Black Sea and might form an important source of nitrite for the anammox reaction.
  • Article
    Compound-specific radiocarbon dating of the varved Holocene sedimentary record of Saanich Inlet, Canada
    (American Geophysical Union, 2004-05-01) Smittenberg, R. H. ; Hopmans, Ellen C. ; Schouten, Stefan ; Hayes, John M. ; Eglinton, Timothy I. ; Sinninghe Damste, Jaap S.
    The radiocarbon contents of various biomarkers extracted from the varve-counted sediments of Saanich Inlet, Canada, were determined to assess their applicability for dating purposes. Calibrated ages obtained from the marine planktonic archaeal biomarker crenarchaeol compared favorably with varve-count ages. The same conclusion could be drawn for a more general archaeal biomarker (GDGT-0), although this biomarker proved to be less reliable due to its less-specific origin. The results also lend support to earlier indications that marine crenarchaeota use dissolved inorganic carbon (DIC) as their carbon source. The average reservoir age offset ΔR of 430 years, determined using the crenarchaeol radiocarbon ages, varied by ±110 years. This may be caused by natural variations in ocean-atmosphere mixing or upwelling at the NE Pacific coast but variability may also be due to an inconsistency in the marine calibration curve when used at sites with high reservoir ages.
  • Article
    Diversity of Archaea and detection of crenarchaeotal amoA genes in the rivers Rhine and Têt
    (Inter-Research, 2009-04-28) Herfort, Lydie ; Kim, Jung-Hyun ; Coolen, Marco J. L. ; Abbas, Ben ; Schouten, Stefan ; Herndl, Gerhard J. ; Sinninghe Damste, Jaap S.
    Pelagic archaeal phylogenetic diversity and the potential for crenarchaeotal nitrification of Group 1.1a were determined in the rivers Rhine and Têt by 16S rRNA sequencing, catalyzed reported deposition-fluorescence in situ hybridization (CARD–FISH) and quantification of 16S rRNA and functional genes. Euryarchaeota were, for the first time, detected in temperate river water even though a net predominance of crenarchaeotal phylotypes was found. Differences in phylogenic distribution were observed between rivers and seasons. Our data suggest that a few archaeal phylotypes (Euryarchaeota Groups RC-V and LDS, Crenarchaeota Group 1.1a) are widely distributed in pelagic riverine environments whilst others (Euryarchaeota Cluster Sagma-1) may only occur seasonally in river water. Crenarchaeota Group 1.1a has recently been identified as a major nitrifier in the marine environment and phylotypes of this group were also present in both rivers, where they represented 0.3% of the total pelagic microbial community. Interestingly, a generally higher abundance of Crenarchaeota Group 1.1a was found in the Rhine than in the Têt, and crenarchaeotal ammonia monooxygenase gene (amoA) was also detected in the Rhine, with higher amoA copy numbers measured in February than in September. This suggests that some of the Crenarchaeota present in river waters have the ability to oxidize ammonia and that riverine crenarchaeotal nitrification of Group 1.1a may vary seasonally.
  • Article
    Ancient DNA derived from alkenone-biosynthesizing haptophytes and other algae in Holocene sediments from the Black Sea
    (American Geophysical Union, 2006-02-18) Coolen, Marco J. L. ; Boere, Arjan C. ; Abbas, Ben ; Baas, Marianne ; Wakeham, Stuart G. ; Sinninghe Damste, Jaap S.
    Holocene sea surface temperatures (SST) of the Black Sea have been reconstructed using sedimentary C37 unsaturated alkenones assumed to be derived from the coccolithophorid haptophyte Emiliania huxleyi, whose fossil coccoliths are an important constituent of the unit I sediments. However, alkenones can also be biosynthesized by haptophyte species that do not produce microscopic recognizable coccoliths. A species-specific identification of haptophytes is important in such U 37 K′-based past SST reconstructions since different species have different alkenone-SST calibrations. We showed that 18S rDNA of E. huxleyi made up only a very small percentage (less than 0.8%) of the total eukaryotic 18S rDNA within the up to 3600-year-old fossil record obtained from the depocenter (>2000 m) of the Black Sea. The predominant fossil 18S rDNA was derived from dinoflagellates (Gymnodinium spp.), which are predominant members of the summer phytoplankton bloom in the modern Black Sea. Using a polymerase chain reaction/denaturing gradient gel electrophoresis method selective for haptophytes, we recovered substantial numbers of a preserved 458-base-pair (bp)-long 18S rDNA fragment of E. huxleyi from the Holocene Black Sea sediments. Additional fossil haptophyte sequences were not detected, indicating that the E. huxleyi alkenone-SST calibration can be applied for at least the last ∼3600 years. The ancient E. huxleyi DNA was well protected against degradation since the DNA/alkenone ratio did not significantly decrease throughout the whole sediment core and 20% of ∼2700-year-old fossil E. huxleyi DNA was still up to 23,000 base pairs long. We showed that fossil DNA offers great potential to study the Holocene paleoecology and paleoenvironment of anoxic deep-sea settings in unprecedented detail.
  • Preprint
    Rapid sulfurisation of highly branched isoprenoid (HBI) alkenes in sulfidic Holocene sediments from Ellis Fjord, Antarctica
    ( 2006-04-03) Sinninghe Damste, Jaap S. ; Rijpstra, W. Irene C. ; Coolen, Marco J. L. ; Schouten, Stefan ; Volkman, John K.
    Samples of particulate organic matter from the water column and anoxic Holocene sediment layers from the Small Meromictic Basin (SMB) in Ellis Fjord (eastern Antarctica) were analyzed to study the early incorporation of reduced inorganic sulfur species into highly branched isoprenoid (HBI) alkenes. HBIs were not detected in the water column samples from austral winter, whereas compounds containing the C25 HBI skeleton were abundant in all analyzed Holocene sediment layers. The structure of the C25:2 HBI alkene together with its enriched stable carbon isotopic composition suggest that the HBI alkene is produced by a diatom or diatoms probably belonging to the Navicula genus present in the sea-ice which covers the area most of the year. Within just 500 years of deposition, all of the HBI alkene was sulfurised. A mixture of products was formed, including components tentatively identified as a C25 HBI thiane and three S-containing dimers composed of two C25:1 HBI skeletons linked together by a sulfide bond. Most of the HBI alkene, however, was converted to polar S-containing compounds. The observed reaction rate for sulfurisation the C25:2 HBI alkene is the highest observed so far in natural systems. Sterols and other lipids known to be prone to sulfurisation were only minimally sulfurised under these depositional conditions. The reason for this is presently unclear.
  • Article
    Exploring preserved fossil dinoflagellate and haptophyte DNA signatures to infer ecological and environmental changes during deposition of sapropel S1 in the eastern Mediterranean
    (American Geophysical Union, 2011-04-16) Boere, Arjan C. ; Rijpstra, W. Irene C. ; de Lange, Gert J. ; Malinverno, Elisa ; Sinninghe Damste, Jaap S. ; Coolen, Marco J. L.
    In this study we used a comparative multiproxy survey (fossil DNA, calcareous nannofossils, and lipid biomarkers) to test whether preserved genetic signatures provide an accurate view of haptophyte and dinoflagellate populations during deposition of the eastern Mediterranean sapropel S1 and the organic carbon-depleted oxidized marls flanking the S1 and to see if we could identify important environmental indicator species that did not fossilize and escaped previous microscopic identification. The marls above and below the S1 contained low concentrations of lipid biomarkers diagnostic for dinoflagellates and haptophytes (i.e., dinosterol and long-chain alkenones), but 500 base pair long ribosomal DNA fragments of these protists were below the detection limit. In contrast, dinoflagellate and haptophyte DNA could be recovered from the organic carbon-rich S1, but the most abundant sequences did not represent species that were part of the nannofossil (this study) or previously described dinocyst composition. The oldest section of S1 (9.8 to ∼8 14C kyr B.P.) revealed a predominance of dinoflagellate phylotypes, which were previously only detected in anoxic Black Sea sediments. In the same section of the core, the most abundant haptophyte sequence showed highest similarity with uncultivated haptophytes that were previously shown to grow mixotrophically as predators of picocyanobacteria, an adaptation that promotes growth in oligotrophic marine waters. Sequences with highest similarities to clones found in marine surface waters predominated in the S1 after ∼8 14C kyr B.P. We discuss whether the shifts in haptophyte and dinoflagellate populations inferred from the preserved DNA reflect known environmental changes that occurred during the formation of sapropel S1.
  • Preprint
    A radiocarbon-based assessment of the preservation characteristics of crenarchaeol and alkenones from continental margin sediments
    ( 2008-01-22) Mollenhauer, Gesine ; Eglinton, Timothy I. ; Hopmans, Ellen C. ; Sinninghe Damste, Jaap S.
    Crenarchaeotal glycerol dibiphytanyl glycerol tetraether (GDGT) lipids and alkenones are two types of biomarkers derived from planktonic marine micro-organisms which are used for reconstruction of sea-surface temperatures. We determined the radiocarbon contents of the archaeal GDGT crenarchaeol and of alkenones isolated from continental margin sediments. Systematic differences were found between the two biomarkers, with higher radiocarbon contents in crenarchaeol than in the phytoplankton-derived alkenones. These differences can be explained by variable contributions of pre-aged, laterally advected material to the core sites. Crenarchaeol appears to be more efficiently degraded during transport in oxygen-replete environments than alkenones. Whether this reflects the influence of chemical structure or mode of protection (e.g., particle association) is not yet known.
  • Article
    Forcing of tropical Atlantic sea surface temperatures during the mid-Pleistocene transition
    (American Geophysical Union, 2004-12-28) Schefuß, Enno ; Sinninghe Damste, Jaap S. ; Jansen, J. H. Fred
    We compare a new mid-Pleistocene sea surface temperature (SST) record from the eastern tropical Atlantic to changes in continental ice volume, orbital insolation, Atlantic deepwater ventilation, and Southern Ocean front positions to resolve forcing mechanisms of tropical Atlantic SST during the mid-Pleistocene transition (MPT). At the onset of the MPT, a strong tropical cooling occurred. The change from a obliquity- to a eccentricity-dominated cyclicity in the tropical SST took place at about 650 kyr BP. In orbital cycles, tropical SST changes significantly preceded continental ice-volume changes but were in phase with movements of Southern Ocean fronts. After the onset of large-amplitude 100-kyr variations, additional late glacial warming in the eastern tropical Atlantic was caused by enhanced return flow of warm waters from the western Atlantic driven by strong trade winds. Pronounced 80-kyr variations in tropical SST occurred during the MPT, in phase with and likely directly forced by transitional continental ice-volume variations. During the MPT, a prominent anomalous long-term tropical warming occurred, likely generated by extremely northward displaced Southern Ocean fronts. While the overall pattern of global climate variability during the MPT was determined by changes in mean state and frequency of continental ice volume variations, tropical Atlantic SST variations were primarily driven by early changes in Subantarctic sea-ice extent and coupled Southern Ocean frontal positions.
  • Preprint
    Evidence for substantial intramolecular heterogeneity in the stable carbon isotopic composition of phytol in photoautotrophic organisms
    ( 2007-09-05) Schouten, Stefan ; Ozdirekcan, Suat ; van der Meer, Marcel T. J. ; Blokker, Peter ; Baas, Marianne ; Hayes, John M. ; Sinninghe Damste, Jaap S.
    The ubiquitous isoprenoid phytol was isolated from a range of algae, terrestrial plants and a bacterium and its two terminal carbon atoms were quantitatively removed by chemical oxidation. The product, 6,10,14-trimethylpentadecan-2-one, was depleted in 13C by 1-4‰ relative to the parent phytol. This difference is significant, and indicates that the pathway for biosynthesis of phytol induces substantial intramolecular stable carbon isotopic fractionations. The nature and magnitude of the fractionations suggest strongly that it is associated both with the biosynthesis of isopentenyl pyrophosphate via the 2-C-methylerythritol-4-phosphate pathway and with the formation of carotenoids and phytol from geranyl-geraniolphosphate. As a result of these large, intramolecular isotopic differences, diagenetic products formed by loss of C, such as pristane, may be naturally depleted in 13C by several permil relative to phytane.
  • Preprint
    Archaeal nitrification in the ocean
    ( 2006-01-30) Wuchter, Cornelia ; Abbas, Ben ; Coolen, Marco J. L. ; Herfort, Lydie ; van Bleijswijk, Judith ; Timmers, Peer ; Strous, Marc ; Teira, Eva ; Herndl, Gerhard J. ; Middelburg, Jack J. ; Schouten, Stefan ; Sinninghe Damste, Jaap S.
    Marine Crenarchaeota are the most abundant single group of prokaryotes in the ocean but their physiology and role in marine biogeochemical cycles are unknown. Recently, a member of this clade was isolated from a sea aquarium and shown to be capable of nitrification, tentatively suggesting that they may play a role in the oceanic nitrogen cycle. We enriched a crenarchaeote from North Sea water and show that it oxidizes ammonium to nitrite. A time series study in the North Sea revealed that the abundance of the gene encoding for the archaeal ammonia monooxygenase alfa subunit (amoA) is correlated with the decline in ammonium concentrations and with the abundance of Crenarcheota. Remarkably, the archaeal amoA abundance was 1-2 orders of magnitude higher than those of bacterial nitrifiers which are commonly thought to mediate the oxidation of ammonium to nitrite in marine environments. Analysis of Atlantic waters of the upper 1000 m, where most of the ammonium regeneration and oxidation takes place, showed that crenarchaeotal amoA copy numbers are also one to three orders of magnitude higher than those of bacterial amoA. Our data thus suggest a major role for Archaea in oceanic nitrification.
  • Article
    Identification of organic matter sources in sulfidic late Holocene Antarctic fjord sediments from fossil rDNA sequence analysis
    (American Geophysical Union, 2007-05-09) Coolen, Marco J. L. ; Volkman, John K. ; Abbas, Ben ; Muyzer, Gerard ; Schouten, Stefan ; Sinninghe Damste, Jaap S.
    The 18S ribosomal DNA (rDNA) isolated from sulfidic Holocene sediments and particulate organic matter in the water column of the stratified Small Meromictic Basin (SMB) in Ellis Fjord (eastern Antarctica) was analyzed to identify possible biological sources of organic matter. Previous work had shown that the sediments contained numerous diatom frustules and high contents of a highly branched isoprenoid (HBI) C25:2 alkene (which is a specific biomarker of certain species of the diatom genera Navicula, Haslea, Pleurosigma, or Rhizosolenia), so we focused our search on preserved fossil 18S rDNA of diatoms using sensitive polymerase chain reaction (PCR) approaches. We did not find diatom-derived fossil 18S rDNA using general eukaryotic primers, and even when we used primers selective for diatom 18S rDNA, we only identified a Chaetoceros phylotype, which is known to form cysts in the SMB but is not a likely source of the C25:2 HBI. When we used PCR/denaturing gradient gel electrophoresis methods specific to phylotypes within the HBI-biosynthesizing genera, we were able to identify three phylotypes in the sediments related to HBI-producing strains of the genera Haslea and Navicula. The ancient DNA data thus provided a limited, but valuable, view of the diversity of late Holocene primary producers with a particular bias to specific components of the biota that were better preserved such as the Chaetoceros cysts. This use of paleogenetics also revealed unexpected possible sources of organic matter such as novel stramenopiles for which no specific lipid biomarkers are known and thus would not have been identified based on traditional lipid stratigraphy alone.
  • Preprint
    An unusual 17α,21β(H)-bacteriohopanetetrol in Holocene sediments from Ace Lake (Antarctica)
    ( 2008-01) Talbot, Helen M. ; Coolen, Marco J. L. ; Sinninghe Damste, Jaap S.
    Whilst investigating the intact biohopanoid (bacteriohopanepolyol, BHP) distribution in Holocene sediments from Ace Lake (Antarctica), we have identified the presence of ab- bacteriohopanetetrol in sediments aged up to 9400 years BP. To our knowledge, this is the first time that an intact polyfunctionalised BHP with the “geological” 17α,21β(H) configuration has been identified in a sediment. Previously, this structure has only been observed in species of the nitrogen fixing bacterium Frankia. Its presence here in the sedimentary environment has implications for the interpretation of hopanoid ββ/αβ ratios in the geological record.
  • Article
    Aging of marine organic matter during cross-shelf lateral transport in the Benguela upwelling system revealed by compound-specific radiocarbon dating
    (American Geophysical Union, 2007-09-18) Mollenhauer, Gesine ; Inthorn, Maik ; Vogt, Thomas ; Zabel, Matthias ; Sinninghe Damste, Jaap S. ; Eglinton, Timothy I.
    Organic matter accumulation and burial on the Namibian shelf and upper slope are spatially heterogeneous and strongly controlled by lateral transport in subsurface nepheloid layers. Much of the material deposited in depo-centers on the slope ultimately derives from the shelf. Supply of organic matter from the shelf involves selective transport of organic matter. We studied these selective transport processes by analyzing the radiocarbon content of co-occurring sediment fractions. Here we present radiocarbon data for total organic carbon as well as three tracers of surface ocean productivity (phytoplankton-derived alkenones, membrane lipids of pelagic crenarchaeota (crenarchaeol), and calcareous microfossils of planktic foraminifera) in core-top and near-surface sediment samples. The samples were collected on the Namibian margin along a shelf-slope transect (85 to 1040 m) at 24°S and from the upper slope depo-center at 25.5°S. In core-top sediments, alkenone ages gradually increased from modern to 3490 radiocarbon years with distance from shore and with water depth. Crenarchaeol, while younger than alkenones, also increased in age with distance offshore. It was concluded that the observed ages were a consequence of cross-shelf transport and associated aging of organic matter. Radiocarbon ages of preserved lipid biomarkers in sediments thus at least partially depend on the relative amount of laterally supplied, pre-aged material present in a sample, highlighting the importance of nepheloid transport for the sedimentation of organic matter over the Namibian margin.
  • Article
    An interlaboratory study of TEX86 and BIT analysis using high-performance liquid chromatography–mass spectrometry
    (American Geophysical Union, 2009-03-20) Schouten, Stefan ; Hopmans, Ellen C. ; van der Meer, Jaap ; Mets, Anchelique ; Bard, Edouard ; Bianchi, Thomas S. ; Diefendorf, Aaron ; Escala, Marina ; Freeman, Katharine H. ; Furukawa, Yoshihiro ; Huguet, Carme ; Ingalls, Anitra ; Menot, Guillemette ; Nederbragt, Alexandra J. ; Oba, Masahiro ; Pearson, Ann ; Pearson, Emma J. ; Rosell-Mele, Antoni ; Schaeffer, Philippe ; Shah, Sunita R. ; Shanahan, Timothy M. ; Smith, Richard W. ; Smittenberg, Rienk ; Talbot, Helen M. ; Uchida, Masao ; Van Mooy, Benjamin A. S. ; Yamamoto, Masanobu ; Zhang, Zhaohui ; Sinninghe Damste, Jaap S.
    Recently, two new proxies based on the distribution of glycerol dialkyl glycerol tetraethers (GDGTs) were proposed, i.e., the TEX86 proxy for sea surface temperature reconstructions and the BIT index for reconstructing soil organic matter input to the ocean. In this study, fifteen laboratories participated in a round robin study of two sediment extracts with a range of TEX86 and BIT values to test the analytical reproducibility and repeatability in analyzing these proxies. For TEX86 the repeatability, indicating intra-laboratory variation, was 0.028 and 0.017 for the two sediment extracts or ±1–2°C when translated to temperature. The reproducibility, indicating among-laboratory variation, of TEX86 measurements was substantially higher, i.e., 0.050 and 0.067 or ±3–4°C when translated to temperature. The latter values are higher than those obtained in round robin studies of Mg/Ca and U37 k′ paleothermometers, suggesting the need to primarily improve compatibility between labs. The repeatability of BIT measurements for the sediment with substantial amounts of soil organic matter input was relatively small, 0.029, but reproducibility was large, 0.410. This large variance could not be attributed to specific equipment used or a particular data treatment. We suggest that this may be caused by the large difference in the molecular weight in the GDGTs used in the BIT index, i.e., crenarchaeol versus the branched GDGTs. Potentially, this difference gives rise to variable responses in the different mass spectrometers used. Calibration using authentic standards is needed to establish compatibility between labs performing BIT measurements.
  • Article
    An interlaboratory study of TEX86 and BIT analysis of sediments, extracts, and standard mixtures
    (John Wiley & Sons, 2013-12-20) Schouten, Stefan ; Hopmans, Ellen C. ; Rosell-Mele, Antoni ; Pearson, Ann ; Adam, Pierre ; Bauersachs, Thorsten ; Bard, Edouard ; Bernasconi, Stefano M. ; Bianchi, Thomas S. ; Brocks, Jochen J. ; Carlson, Laura Truxal ; Castaneda, Isla S. ; Derenne, Sylvie ; Selver, Ayca Dogrul ; Dutta, Koushik ; Eglinton, Timothy I. ; Fosse, Celine ; Galy, Valier ; Grice, Kliti ; Hinrichs, Kai-Uwe ; Huang, Yongsong ; Huguet, Arnaud ; Huguet, Carme ; Hurley, Sarah ; Ingalls, Anitra ; Jia, Guodong ; Keely, Brendan ; Knappy, Chris ; Kondo, Miyuki ; Krishnan, Srinath ; Lincoln, Sara ; Lipp, Julius S. ; Mangelsdorf, Kai ; Martínez-Garcia, Alfredo ; Menot, Guillemette ; Mets, Anchelique ; Mollenhauer, Gesine ; Ohkouchi, Naohiko ; Ossebaar, Jort ; Pagani, Mark ; Pancost, Richard D. ; Pearson, Emma J. ; Peterse, Francien ; Reichart, Gert-Jan ; Schaeffer, Philippe ; Schmitt, Gaby ; Schwark, Lorenz ; Shah, Sunita R. ; Smith, Richard W. ; Smittenberg, Rienk H. ; Summons, Roger E. ; Takano, Yoshinori ; Talbot, Helen M. ; Taylor, Kyle W. R. ; Tarozo, Rafael ; Uchida, Masao ; van Dongen, Bart E. ; Van Mooy, Benjamin A. S. ; Wang, Jinxiang ; Warren, Courtney ; Weijers, Johan W. H. ; Werne, Josef P. ; Woltering, Martijn ; Xie, Shucheng ; Yamamoto, Masanobu ; Yang, Huan ; Zhang, Chuanlun L. ; Zhang, Yige ; Zhao, Meixun ; Sinninghe Damste, Jaap S.
    Two commonly used proxies based on the distribution of glycerol dialkyl glycerol tetraethers (GDGTs) are the TEX86 (TetraEther indeX of 86 carbon atoms) paleothermometer for sea surface temperature reconstructions and the BIT (Branched Isoprenoid Tetraether) index for reconstructing soil organic matter input to the ocean. An initial round-robin study of two sediment extracts, in which 15 laboratories participated, showed relatively consistent TEX86 values (reproducibility ±3–4°C when translated to temperature) but a large spread in BIT measurements (reproducibility ±0.41 on a scale of 0–1). Here we report results of a second round-robin study with 35 laboratories in which three sediments, one sediment extract, and two mixtures of pure, isolated GDGTs were analyzed. The results for TEX86 and BIT index showed improvement compared to the previous round-robin study. The reproducibility, indicating interlaboratory variation, of TEX86 values ranged from 1.3 to 3.0°C when translated to temperature. These results are similar to those of other temperature proxies used in paleoceanography. Comparison of the results obtained from one of the three sediments showed that TEX86 and BIT indices are not significantly affected by interlaboratory differences in sediment extraction techniques. BIT values of the sediments and extracts were at the extremes of the index with values close to 0 or 1, and showed good reproducibility (ranging from 0.013 to 0.042). However, the measured BIT values for the two GDGT mixtures, with known molar ratios of crenarchaeol and branched GDGTs, had intermediate BIT values and showed poor reproducibility and a large overestimation of the “true” (i.e., molar-based) BIT index. The latter is likely due to, among other factors, the higher mass spectrometric response of branched GDGTs compared to crenarchaeol, which also varies among mass spectrometers. Correction for this different mass spectrometric response showed a considerable improvement in the reproducibility of BIT index measurements among laboratories, as well as a substantially improved estimation of molar-based BIT values. This suggests that standard mixtures should be used in order to obtain consistent, and molar-based, BIT values.
  • Article
    Correction to “Forcing of tropical Atlantic sea surface temperatures during the mid-Pleistocene transition”
    (American Geophysical Union, 2005-03-30) Schefuß, Enno ; Sinninghe Damste, Jaap S. ; Jansen, J. H. Fred