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  • 2015-2019  (135)
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  • 1
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    Life on the edge: active microbial communities in the Kryos MgCl2-brine basin at very low water activity (2018)
    Nature Research
    In:  The ISME Journal, 12 (6). pp. 1414-1426.
    Details
    Publication Date: 2021-02-08
    Description: The Kryos Basin is a deep-sea hypersaline anoxic basin (DHAB) located in the Eastern Mediterranean Sea (34.98°N 22.04°E). It is filled with brine of re-dissolved Messinian evaporites and is nearly saturated with MgCl2-equivalents, which makes this habitat extremely challenging for life. The strong density difference between the anoxic brine and the overlying oxic Mediterranean seawater impedes mixing, giving rise to a narrow chemocline. Here, we investigate the microbial community structure and activities across the seawater–brine interface using a combined biogeochemical, next-generation sequencing, and lipid biomarker approach. Within the interface, we detected fatty acids that were distinctly 13C-enriched when compared to other fatty acids. These likely originated from sulfide-oxidizing bacteria that fix carbon via the reverse tricarboxylic acid cycle. In the lower part of the interface, we also measured elevated rates of methane oxidation, probably mediated by aerobic methanotrophs under micro-oxic conditions. Sulfate reduction rates increased across the interface and were highest within the brine, providing first evidence that sulfate reducers (likely Desulfovermiculus and Desulfobacula) thrive in the Kryos Basin at a water activity of only ~0.4 Aw. Our results demonstrate that a highly specialized microbial community in the Kryos Basin has adapted to the poly-extreme conditions of a DHAB with nearly saturated MgCl2 brine, extending the known environmental range where microbial life can persist.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1038/s41396-018-0107-z
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    A continental-weathering control on orbitally driven redox-nutrient cycling during Cretaceous Oceanic Anoxic Event 2 (2015)
    GSA, Geological Society of America
    In:  Geology, 43 (11). pp. 963-966.
    Details
    Publication Date: 2019-09-23
    Description: The Cretaceous period (similar to 145-65 m.y. ago) was characterized by intervals of enhanced organic carbon burial associated with increased primary production under greenhouse conditions. The global consequences of these perturbations, oceanic anoxic events (OAEs), lasted up to 1 m.y., but short-term nutrient and climatic controls on widespread anoxia are poorly understood. Here, we present a high-resolution reconstruction of oceanic redox and nutrient cycling as recorded in subtropical shelf sediments from Tarfaya, Morocco, spanning the initiation of OAE2. Iron-sulfur systematics and biomarker evidence demonstrate previously undescribed redox cyclicity on orbital time scales, from sulfidic to anoxic ferruginous (Fe-rich) water-column conditions. Bulk geochemical data and sulfur isotope modeling suggest that ferruginous conditions were not a consequence of nutrient or sulfate limitation, despite overall low sulfate concentrations in the proto-North Atlantic. Instead, fluctuations in the weathering influxes of sulfur and reactive iron, linked to a dynamic hydrological cycle, likely drove the redox cyclicity. Despite the potential for elevated phosphorus burial in association with Fe oxides under ferruginous conditions on the Tarfaya shelf, porewater sulfide generation drove extensive phosphorus recycling back to the water column, thus maintaining widespread open-ocean anoxia.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1130/G36837.1
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Response of the North Atlantic surface and intermediate ocean structure to climate warming of MIS 11 (2017)
    Nature Research
    In:  Scientific Reports, 7 (46192).
    Details
    Publication Date: 2020-06-18
    Description: Investigating past interglacial climates not only help to understand how the climate system operates in general, it also forms a vital basis for climate predictions. We reconstructed vertical stratification changes in temperature and salinity in the North Atlantic for a period some 400 ka ago (MIS11), an interglacial time analogue of a future climate. As inferred from a unique set of biogeochemical, geochemical, and faunal data, the internal upper ocean stratification across MIS 11 shows distinct depth-dependent dynamical changes related to vertical as well as lateral shifts in the upper Atlantic meridional circulation system. Importantly, transient cold events are recognized near the end of the long phase of postglacial warming at surface, subsurface, mid, and deeper water layers. These data demonstrate that MIS 11 coolings over the North Atlantic were initially triggered by freshwater input at the surface and expansion of cold polar waters into the Subpolar Gyre. The cooling signal was then transmitted downwards into mid-water depths. Since the cold events occurred after the main deglacial phase we suggest that their cause might be related to continuous melting of the Greenland ice sheet, a mechanism that might also be relevant for the present and upcoming climate.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1038/srep46192
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Long-chain diols in rivers: distribution and potential biological sources (2018)
    In:  EPIC3Biogeosciences, 15(13), pp. 4147-4161, ISSN: 1726-4189
    Details
    Publication Date: 2018-09-10
    Description: Long-chain diols (LCDs) occur widespread in marine environments and also in lakes and rivers. Transport of LCDs from rivers may impact the distribution of LCDs in coastal environments, however relatively little is known about the distribution and biological sources of LCDs in river systems. In this study, we investigated the distribution of LCDs in suspended particulate matter (SPM) of three river systems (Godavari, Danube, and Rhine) in relation with precipitation, temperature, and source catchments. The dominant long-chain diol is the C32 1,15-diol followed by the C30 1,15-diol in all studied river systems. In regions influenced by marine waters, such as delta systems, the fractional abundance of the C30 1,15-diol is substantially higher than in the river itself, suggesting different LCD producers in marine and freshwater environments. A change in the LCD distribution along the downstream transects of the rivers studied was not observed. However, an effect of river flow is observed; i.e., the concentration of the C32 1,15-diol is higher in stagnant waters such as reservoirs and during seasons with river low stands. A seasonal change in the LCD distribution was observed in the Rhine, likely due to a change in the producers. Eukaryotic diversity analysis by 18S rRNA gene sequencing of SPM from the Rhine showed extremely low abundances of sequences (i.e., 〈0.32% of total reads) related to known algal LCD producers. Furthermore, incubation of the river water with 13C-labeled bicarbonate did not result in 13C incorporation into LCDs. This indicates that the LCDs present are mainly of fossil origin in the fast-flowing part of the Rhine. Overall, our results suggest that the LCD producers in rivers predominantly reside in lakes or side ponds that are part of the river system.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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    PAPER (OA)
  • 5
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    Bisnorgammacerane traces predatory pressure and the persistent rise of algal ecosystems after Snowball Earth (2019)
    In:  EPIC3Nature Communications, 10(1), ISSN: 2041-1723
    Details
    Publication Date: 2019-02-25
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 6
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    A four-year record of UK′37- and TEX86-derived sea surface temperature estimates from sinking particles in the filamentous upwelling region off Cape Blanc, Mauritania (2015)
    In:  EPIC3Deep Sea Research Part I: Oceanographic Research Papers, 97, pp. 67-79, ISSN: 09670637
    Details
    Publication Date: 2015-07-02
    Description: Lipid biomarker records from sinking particles collected by sediment traps can be used to study the seasonality of biomarker production as well as processes of particle formation and settling, ultimately leading to the preservation of the biomarkers in sediments. Here we present records of the biomarker indices based on alkenones and TEX86 based on isoprenoid glycerol dialkyl glycerol tetraethers (GDGTs), both used for the reconstruction of sea surface temperatures (SST). These records were obtained from sinking particles collected using a sediment trap moored in the filamentous upwelling zone off Cape Blanc, Mauritania, at approximately 1300 water depth during a four-year time interval between 2003 and 2007, and supplemented by and TEX86 determined on suspended particulate matter collected from surface waters in the study area. Mass and lipid fluxes are highest during peak upwelling periods between October and June. The alkenone and GDGT records both display pronounced seasonal variability. Sinking velocities calculated from the time lag between measured SST maxima and minima and corresponding index maxima and minima in the trap samples are higher for particles containing alkenones (14-59 m d-1) than for GDGTs (9-17 m d-1). It is suggested that GDGTs are predominantly exported from shallow waters by incorporation in opal-rich particles. SST estimates based on the index correspond to the amplitude observed fluctuations in SST during the study period. Temperature estimates based on TEX86 show smaller seasonal amplitudes, which can be explained by either predominant production of GDGTs during the warm season, or a contribution of GDGTs exported from deep waters, which are in this region known to carry GDGTs in a distribution that translates to a high TEX86 signal.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 7
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    Bacterial GMGTs in East African lake sediments: Their potential as palaeotemperature indicators (2019)
    PANGAEA
    In:  Supplement to: Baxter, Allix J; Hopmans, Ellen C; Russell, James M; Sinninghe Damsté, Jaap S (2019): Bacterial GMGTs in East African lake sediments: Their potential as palaeotemperature indicators. Geochimica et Cosmochimica Acta, 259, 155-169, https://doi.org/10.1016/j.gca.2019.05.039
    Details
    Publication Date: 2023-03-14
    Description: Glycerol monoalkyl glycerol tetraethers (GMGTs) are a group of membrane spanning lipids produced by some species of archaea and bacteria. They differ from the more commonly studied glycerol dialkyl glycerol tetraethers (GDGTs) in having an additional covalent carbon-carbon bond connecting the two alkyl chain. The relative abundance and distribution of bacterial branched GMGTs (brGMGTs) in surface sediments from a set of East African lakes were studied. The abundance of brGMGTs relative to the brGDGTs is positively correlated to measured mean annual air temperature (MAAT), although with a significant amount of scatter. BrGMGT abundance was not correlated to lake water pH. Seven major brGMGTs that vary in degree of methylation were identified, with m/z 1020, 1034 and 1048. Further, the mass chromatograms of the m/z 1020 and 1034 brGMGTs show an interesting distribution of peaks, which likely relates to the occurrence of distinct brGMGT isomers. This structural complexity is higher than previously observed in peats and marine sediments. Principal component analysis of the fractional abundance of bacterial tetraether lipids revealed the brGMGTs behave similarly to one another but differently from both the 5- or 6-methyl brGDGTs. This suggests the brGMGTs are produced by a common source organism and are methylated at a different position. The distribution of the seven brGMGTs showed considerable correlation with MAAT. This variability was captured in a new proxy index (the brGMGTI), which showed a strong positive linear relationship with MAAT. Lacustrine brGMGTs show potential to be applied to ancient settings to provide information about paleoclimate.
    Keywords: Albert_Lake; Bandara_Lake; Batoda_Lake; Bigata_Lake; Branched glycerol dialkyl glycerol tetraether, Ia; Branched glycerol dialkyl glycerol tetraether, Ia (peak area); Branched glycerol dialkyl glycerol tetraether, Ib; Branched glycerol dialkyl glycerol tetraether, Ib (peak area); Branched glycerol dialkyl glycerol tetraether, Ic; Branched glycerol dialkyl glycerol tetraether, Ic (peak area); Branched glycerol dialkyl glycerol tetraether, IIa; Branched glycerol dialkyl glycerol tetraether, IIa'; Branched glycerol dialkyl glycerol tetraether, IIa' (peak area); Branched glycerol dialkyl glycerol tetraether, IIa (peak area); Branched glycerol dialkyl glycerol tetraether, IIb; Branched glycerol dialkyl glycerol tetraether, IIb'; Branched glycerol dialkyl glycerol tetraether, IIb' (peak area); Branched glycerol dialkyl glycerol tetraether, IIb (peak area); Branched glycerol dialkyl glycerol tetraether, IIIa; Branched glycerol dialkyl glycerol tetraether, IIIa'; Branched glycerol dialkyl glycerol tetraether, IIIa' (peak area); Branched glycerol dialkyl glycerol tetraether, IIIa (peak area); Branched glycerol monoalkyl glycerol tetraethers, H1020a; Branched glycerol monoalkyl glycerol tetraethers, H1020a (peak area); Branched glycerol monoalkyl glycerol tetraethers, H1020b; Branched glycerol monoalkyl glycerol tetraethers, H1020b (peak area); Branched glycerol monoalkyl glycerol tetraethers, H1020c; Branched glycerol monoalkyl glycerol tetraethers, H1020c (peak area); Branched glycerol monoalkyl glycerol tetraethers, H1034a; Branched glycerol monoalkyl glycerol tetraethers, H1034a (peak area); Branched glycerol monoalkyl glycerol tetraethers, H1034b; Branched glycerol monoalkyl glycerol tetraethers, H1034b (peak area); Branched glycerol monoalkyl glycerol tetraethers, H1034c; Branched glycerol monoalkyl glycerol tetraethers, H1034c (peak area); Branched glycerol monoalkyl glycerol tetraethers, H1048; Branched glycerol monoalkyl glycerol tetraethers, H1048 (peak area); Bugwagi_Lake; Bukurungu_East_Lake; Central_Lake; Chibwera_Lake; Country; Crane_Lake; DEPTH, water; Dimtu_Lake; Edward_Lake; Elevation of event; Enchanted_Lake__Lake; Event label; Gallery_Tarn_Lake; Garba_Gurach_Lake; GDGTs; GMGT; Hanging_Tarn_Lake; Hara_Laki_Lake; Hara_Lucas_Lake; Haro_Lakota_Lake; Harris_Tarn_Lake; Hausburg_Tarn_Lake; H-GDGT; Hut_Tarn_Lake; Ibamba_Lake; Kacuba_Lake; Kako_Lake; Kamweru_Lake; Kanyabutetere_Lake; Kanyanchu_Lake; Kasirya_Lake; Katanda_Lake; Katunda_Lake; Kifuruka_Lake; Kisibendi_Lake; Kitere_Lake; Kopello_Lake; Koromi_Lake; Kuware_Lake; Kyasunduka_Lake; Kyerbwato_Lake; Kyogo_Lake; Lake; Lake_Ellis; lakes; Lake surface area; Large_Hall_Tarn_Lake; Latitude of event; Longitude of event; Lower_Kachope_Lake; Lower_Simba_Lake; Mahoma_Lake; Mahuhura_Lake; Mbayo_Lake; membrane lipids; Middle_Kachope_Lake; Mirambi_Lake; MULT; Multiple investigations; Murabio_Lake; Murusi_Lake; Mwengenyi_Lake; Nanyuki_Tarn_Lake; NIOZ_UU; NIOZ Royal Netherlands Institute for Sea Research, and Utrecht University; Njarayabana_Lake; Nkuruba_Lake; Nyamugosani_Lake; Nyamusingere_Lake; Nyantonde_Lake; Oblong_Tarn_Lake; palaeotemperature; pH; Ruhandika_Lake; Rutundu_Lake; sediments; Small_Hall_Tarn_Lake; Square_Tarn_Lake; Sum; Tanganyika_Lake; Teleki_Tarn_Lake; Temperature, air, annual mean; Temperature, water; tetraethers; Thompson_Lake_Lake; Togona_Lake; Veggi_Tarn_Lake; Wandakara_Lake; Wankenzi_Lake
    Type: Dataset
    Format: text/tab-separated-values, 2991 data points
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    DATA PANGAEA
  • 8
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    (Table 2) Branched GDGT concentrations and proxy values for Svalbard soils, coals seam, beach sand, and freshly weathered rock (2017)
    PANGAEA
    Details
    Publication Date: 2023-03-24
    Keywords: AWIPEV; AWIPEV_based; Branched and isoprenoid tetraether index; Branched glycerol dialkyl glycerol tetraether; Branched glycerol dialkyl glycerol tetraether, Ia; Branched glycerol dialkyl glycerol tetraether, Ib; Branched glycerol dialkyl glycerol tetraether, Ic; Branched glycerol dialkyl glycerol tetraether, IIa; Branched glycerol dialkyl glycerol tetraether, IIb; Branched glycerol dialkyl glycerol tetraether, IIc; Branched glycerol dialkyl glycerol tetraether, IIIa; Branched glycerol dialkyl glycerol tetraether, IIIb; Branched glycerol dialkyl glycerol tetraether, IIIc; Cyclization ratio of branched tetraethers; DEPTH, soil; Event label; Lilliehookbreen-1; Methylation index of branched tetraethers; Mitra-Peninsula-1; Mitra-Peninsula-2; Mitra-Peninsula-3; Mitra-Peninsula-4; Mitra-Peninsula-5; Mitra-Peninsula-6; MULT; Multiple investigations; NIOZ_UU; NIOZ Royal Netherlands Institute for Sea Research, and Utrecht University; Ny-Alesund-1; Ny-Alesund-2; Spitsbergen; Temperature, annual mean
    Type: Dataset
    Format: text/tab-separated-values, 110 data points
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    DATA PANGAEA
  • 9
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    (Table 1) Description and general properties of Svalbard soils, coal seam, beach sand, and freshly weathered rock (2017)
    PANGAEA
    Details
    Publication Date: 2023-03-24
    Keywords: AWIPEV; AWIPEV_based; Carbon, organic, total; DEPTH, soil; Event label; Latitude of event; Lilliehookbreen-1; Lilliehookbreen-2; Lithology/composition/facies; Longitude of event; Mitra-Peninsula-1; Mitra-Peninsula-2; Mitra-Peninsula-3; Mitra-Peninsula-4; Mitra-Peninsula-5; Mitra-Peninsula-6; MULT; Multiple investigations; NIOZ_UU; NIOZ Royal Netherlands Institute for Sea Research, and Utrecht University; Ny-Alesund-1; Ny-Alesund-2; Ny-Alesund-3; Ny-Alesund-4; pH; Spitsbergen
    Type: Dataset
    Format: text/tab-separated-values, 35 data points
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    DATA PANGAEA
  • 10
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    n-Alkane in aerosols across the tropical North Atlantic (2017)
    PANGAEA
    Details
    Publication Date: 2023-03-10
    Keywords: 64PE395; 64PE395-13_AIR; 64PE395-14_AIR; 64PE395-15_AIR; 64PE395-16_AIR; 64PE395-17_AIR; 64PE395-18_AIR; 64PE395-19_AIR; 64PE395-20_AIR; 64PE395-21_AIR; 64PE395-22_AIR; 64PE395-23_AIR; 64PE395-24_AIR; 64PE395-25_AIR; 64PE395-26_AIR; ALTITUDE; Average chain length; Carbon Preference Index; DUC; Dust collector; DUSTTraffic III; Event label; Latitude of event; Longitude of event; n-Alcohol C27; n-Alcohol C28; n-Alcohol C29; n-Alcohol C30; n-Alcohol C31; n-Alcohol C32; n-Alkane C15; n-Alkane C16; n-Alkane C17; n-Alkane C18; n-Alkane C19; n-Alkane C20; n-Alkane C21; n-Alkane C22; n-Alkane C23; n-Alkane C24; n-Alkane C25; n-Alkane C26; n-Alkane C27; n-Alkane C28; n-Alkane C29; n-Alkane C30; n-Alkane C31; n-Alkane C32; n-Alkane C33; n-Alkane C34; n-fatty acid C27; n-fatty acid C28; n-fatty acid C29; n-fatty acid C30; n-fatty acid C31; n-fatty acid C32; NIOZ_UU; NIOZ Royal Netherlands Institute for Sea Research, and Utrecht University; Pelagia; Ratio; South Atlantic Ocean; sum n-Alcohols C28+C30+C32; Sum n-alkanes C25-C33; sum n-fatty acids C28+C30+C32; Volume
    Type: Dataset
    Format: text/tab-separated-values, 600 data points
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