Heim, Christine N.

[["dc.bibliographiccitation.artnumber","7020"],["dc.bibliographiccitation.journal","Nature Communications"],["dc.bibliographiccitation.volume","6"],["dc.contributor.author","Drake, Henrik"],["dc.contributor.author","Astrom, Mats E."],["dc.contributor.author","Heim, Christine"],["dc.contributor.author","Broman, Curt"],["dc.contributor.author","Astrom, Jan"],["dc.contributor.author","Whitehouse, Martin J."],["dc.contributor.author","Ivarsson, Magnus"],["dc.contributor.author","Siljestrom, Sandra"],["dc.contributor.author","Sjovall, Peter"],["dc.date.accessioned","2018-11-07T09:57:35Z"],["dc.date.available","2018-11-07T09:57:35Z"],["dc.date.issued","2015"],["dc.description.abstract","Precipitation of exceptionally C-13-depleted authigenic carbonate is a result of, and thus a tracer for, sulphate-dependent anaerobic methane oxidation, particularly in marine sediments. Although these carbonates typically are less depleted in C-13 than in the source methane, because of incorporation of C also from other sources, they are far more depleted in C-13 (delta C-13 as light as - 69% V-PDB) than in carbonates formed where no methane is involved. Here we show that oxidation of biogenic methane in carbon-poor deep groundwater in fractured granitoid rocks has resulted in fracture-wall precipitation of the most extremely C-13-depleted carbonates ever reported, delta C-13 down to - 125% V-PDB. A microbial consortium of sulphate reducers and methane oxidizers has been involved, as revealed by biomarker signatures in the carbonates and S-isotope compositions of co-genetic sulphide. Methane formed at shallow depths has been oxidized at several hundred metres depth at the transition to a deep-seated sulphate-rich saline water. This process is so far an unrecognized terrestrial sink of methane."],["dc.identifier.doi","10.1038/ncomms8020"],["dc.identifier.isi","000355529900003"],["dc.identifier.pmid","25948095"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/13588"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/37195"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.relation.issn","2041-1723"],["dc.rights","CC BY 4.0"],["dc.rights.uri","https://creativecommons.org/licenses/by/4.0/"],["dc.title","Extreme C-13 depletion of carbonates formed during oxidation of biogenic methane in fractured granite"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","e0177542"],["dc.bibliographiccitation.issue","5"],["dc.bibliographiccitation.journal","PLoS ONE"],["dc.bibliographiccitation.volume","12"],["dc.contributor.author","Heim, Christine N."],["dc.contributor.author","Quéric, Nadia Valérie"],["dc.contributor.author","Lonescu, Danny"],["dc.contributor.author","Schaefer, Nadine"],["dc.contributor.author","Reitner, Joachim"],["dc.date.accessioned","2018-11-07T10:23:44Z"],["dc.date.available","2018-11-07T10:23:44Z"],["dc.date.issued","2017"],["dc.description.abstract","Stromatolitic iron-rich structures have been reported from many ancient environments and are often described as Frutexites, a cryptic microfossil. Although microbial formation of such structures is likely, a clear relation to a microbial precursor is lacking so far. Here we report recent iron oxidizing biofilms which resemble the ancient Frutexites structures. The living Frutexites-like biofilms were sampled at 160 m depth in the Aspo Hard Rock Laboratory in Sweden. Investigations using microscopy, 454 pyrosequencing, FISH, Raman spectros-copy, biomarker and trace element analysis allowed a detailed view of the structural components of the mineralized biofilm. The most abundant bacterial groups were involved in nitrogen and iron cycling. Furthermore, Archaea are widely distributed in the Frutexites-like biofilm, even though their functional role remains unclear. Biomarker analysis revealed abundant sterols in the biofilm most likely from algal and fungal origins. Our results indicate that the Frutexites-like biofilm was built up by a complex microbial community. The functional role of each community member in the formation of the dendritic structures, as well as their potential relation to fossil Frutexites remains under investigation."],["dc.description.sponsorship","Open-Access-Publikationsfonds 2017"],["dc.identifier.doi","10.1371/journal.pone.0177542"],["dc.identifier.isi","000401672600015"],["dc.identifier.pmid","28542238"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/14488"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/42518"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","PUB_WoS_Import"],["dc.relation.issn","1932-6203"],["dc.rights","CC BY 4.0"],["dc.rights.uri","https://creativecommons.org/licenses/by/4.0/"],["dc.title","Frutexites-like structures formed by iron oxidizing biofilms in the continental subsurface (Aspo Hard Rock Laboratory, Sweden)"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","4736"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","Nature Communications"],["dc.bibliographiccitation.volume","10"],["dc.contributor.author","Drake, Henrik"],["dc.contributor.author","Roberts, Nick M. W."],["dc.contributor.author","Heim, Christine"],["dc.contributor.author","Whitehouse, Martin J."],["dc.contributor.author","Siljestrom, Sandra"],["dc.contributor.author","Kooijman, Ellen"],["dc.contributor.author","Broman, Curt"],["dc.contributor.author","Ivarsson, Magnus"],["dc.contributor.author","Astrom, Mats E."],["dc.date.accessioned","2019-11-12T13:26:18Z"],["dc.date.available","2019-11-12T13:26:18Z"],["dc.date.issued","2019"],["dc.description.abstract","Fractured rocks of impact craters may be suitable hosts for deep microbial communities on Earth and potentially other terrestrial planets, yet direct evidence remains elusive. Here, we present a study of the largest crater of Europe, the Devonian Siljan structure, showing that impact structures can be important unexplored hosts for long-term deep microbial activity. Secondary carbonate minerals dated to 80 ± 5 to 22 ± 3 million years, and thus postdating the impact by more than 300 million years, have isotopic signatures revealing both microbial methanogenesis and anaerobic oxidation of methane in the bedrock. Hydrocarbons mobilized from matured shale source rocks were utilized by subsurface microorganisms, leading to accumulation of microbial methane mixed with a thermogenic and possibly a minor abiotic gas fraction beneath a sedimentary cap rock at the crater rim. These new insights into crater hosted gas accumulation and microbial activity have implications for understanding the astrobiological consequences of impacts."],["dc.identifier.doi","10.1038/s41467-019-12728-y"],["dc.identifier.pmid","31628335"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/16664"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/62602"],["dc.language.iso","en"],["dc.notes.intern","Merged from goescholar"],["dc.relation.eissn","2041-1723"],["dc.relation.issn","2041-1723"],["dc.rights","CC BY 4.0"],["dc.rights.uri","https://creativecommons.org/licenses/by/4.0"],["dc.title","Timing and origin of natural gas accumulation in the Siljan impact structure, Sweden"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","459"],["dc.bibliographiccitation.journal","Frontiers in Microbiology"],["dc.bibliographiccitation.volume","5"],["dc.contributor.author","Ionescu, Danny"],["dc.contributor.author","Buchmann, Bettina"],["dc.contributor.author","Heim, Christine"],["dc.contributor.author","de Beer, Dirk"],["dc.contributor.author","Polerecky, Lubos"],["dc.contributor.author","Häusler, Stefan"],["dc.date.accessioned","2018-11-07T09:35:23Z"],["dc.date.available","2018-11-07T09:35:23Z"],["dc.date.issued","2014"],["dc.description.abstract","If O-2 is available at circumneutral pH, Fe2+ is rapidly oxidized to Fe3+, which precipitates as FeO(OH). Neutrophilic iron oxidizing bacteria have evolved mechanisms to prevent self-encrustation in iron. Hitherto, no mechanism has been proposed for cyanobacteria from Fe2+-rich environments; these produce O-2 but are seldom found encrusted in iron. We used two sets of illuminated reactors connected to two groundwater aquifers with different Fe2+ concentrations (0.9 mu M vs. 26 mu M) in the Aspo Hard Rock Laboratory (HRL), Sweden. Cyanobacterial biofilms developed in all reactors and were phylogenetically different between the reactors. Unexpectedly, cyanobacteria growing in the Fe2+-poor reactors were encrusted in iron, whereas those in the Fe2+-rich reactors were not. In-situ microsensor measurements showed that O-2 concentrations and pH near the surface of the cyanobacterial biofilms from the Fe2+-rich reactors were much higher than in the overlying water. This was not the case for the biofilms growing at low Fe2+ concentrations. Measurements with enrichment cultures showed that cyanobacteria from the Fe2+-rich environment increased their photosynthesis with increasing Fe2+ concentrations, whereas those from the low Fe2+ environment were inhibited at Fe2+ > 5 mu M. Modeling based on in-situ O-2 and pH profiles showed that cyanobacteria from the Fe2+-rich reactor were not exposed to significant Fe2+ concentrations. We propose that, due to limited mass transfer, high photosynthetic activity in Fe2+-rich environments forms a protective zone where Fe2+ precipitates abiotically at a non-lethal distance from the cyanobacteria. This mechanism sheds new light on the possible role of cyanobacteria in precipitation of banded iron formations."],["dc.description.sponsorship","DFG (German Research Foundation) research unit FOR 571"],["dc.identifier.doi","10.3389/fmicb.2014.00459"],["dc.identifier.isi","000341683600001"],["dc.identifier.pmid","25228899"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/11793"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/32374"],["dc.language.iso","en"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Frontiers Media S.A."],["dc.relation.eissn","1664-302X"],["dc.relation.issn","1664-302X"],["dc.rights","CC BY 3.0"],["dc.rights.uri","https://creativecommons.org/licenses/by/3.0/"],["dc.title","Oxygenic photosynthesis as a protection mechanism for cyanobacteria against iron-encrustation in environments with high Fe2+ concentrations"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","6"],["dc.bibliographiccitation.journal","Frontiers in Earth Science"],["dc.bibliographiccitation.volume","3"],["dc.contributor.author","Heim, Christine N."],["dc.contributor.author","Simon, Klaus"],["dc.contributor.author","Ionescu, Danny"],["dc.contributor.author","Reimer, Andreas"],["dc.contributor.author","de Beer, Dirk"],["dc.contributor.author","Quéric, Nadia Valérie"],["dc.contributor.author","Reitner, Joachim"],["dc.contributor.author","Thiel, Volker"],["dc.date.accessioned","2019-07-09T11:41:14Z"],["dc.date.available","2019-07-09T11:41:14Z"],["dc.date.issued","2015"],["dc.description.abstract","Microbial iron oxyhydroxides are common deposits in natural waters, recent sediments, and mine drainage systems. Along with these minerals, trace and rare earth elements (TREE) are being accumulated within the mineralizing microbial mats. TREE patterns are widely used to characterize minerals and rocks, and to elucidate their evolution and origin. However, whether and which characteristic TREE signatures distinguish between a biological and an abiological origin of iron minerals is still not well-understood. Here we report on long-term flow reactor studies performed in the Tunnel of Äspö (Äspö Hard Rock Laboratory, Sweden). The development of microbial mats dominated by iron-oxidizing bacteria (FeOB), namely Mariprofundus sp. and Gallionella sp were investigated. The feeder fluids of the flow reactors were tapped at 183 and 290 m below sea-level from two brackish, but chemically different aquifers within the surrounding, ~1.8 Ga old, granodioritic rocks. The experiments investigated the accumulation and fractionation of TREE under controlled conditions of the subsurface continental biosphere, and enabled us to assess potential biosignatures evolving within the microbial iron oxyhydroxides. After 2 and 9 months, concentrations of Be, Y, Zn, Zr, Hf, W, Th, Pb, and U in the microbial mats were 103- to 105-fold higher than in the feeder fluids whereas the rare earth elements and Y (REE+Y) contents were 104- and 106-fold enriched. Except for a hydrothermally induced Eu anomaly, the normalized REE+Y patterns of the microbial iron oxyhydroxides were very similar to published REE+Y distributions of Archaean Banded Iron Formations (BIFs). The microbial iron oxyhydroxides from the flow reactors were compared to iron oxyhydroxides that were artificially precipitated from the same feeder fluid. Remarkably, these abiotic and inorganic iron oxyhydroxides show the same REE+Y distribution patterns. Our results indicate that the REE+Y mirror closely the water chemistry, but they do not allow to distinguish microbially mediated from inorganic iron precipitates. Likewise, all TREE studied showed an overall similar fractionation behavior in biogenic, abiotic, and inorganic iron oxyhydroxides. Exceptions are Ni and Tl, which were only accumulated in the microbial iron oxyhydroxides and may point to a potential utility of these elements as microbial biosignatures."],["dc.identifier.doi","10.3389/feart.2015.00006"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/11851"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/58377"],["dc.language.iso","en"],["dc.notes.intern","Merged from goescholar"],["dc.publisher","Frontiers Media S.A."],["dc.relation.eissn","2296-6463"],["dc.relation.issn","2296-6463"],["dc.rights","CC BY 4.0"],["dc.rights.uri","https://creativecommons.org/licenses/by/4.0/"],["dc.title","Assessing the utility of trace and rare earth elements as biosignatures in microbial iron oxyhydroxides"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","2032"],["dc.bibliographiccitation.issue","13"],["dc.bibliographiccitation.journal","Water"],["dc.bibliographiccitation.volume","14"],["dc.contributor.author","Zeman-Kuhnert, Sebastian"],["dc.contributor.author","Thiel, Volker"],["dc.contributor.author","Heim, Christine"],["dc.date.accessioned","2022-06-27T10:43:59Z"],["dc.date.available","2022-06-27T10:43:59Z"],["dc.date.issued","2022"],["dc.date.updated","2022-07-08T13:37:56Z"],["dc.description.abstract","The formation of algal and cyanobacterial blooms caused by the eutrophication of water bodies is a growing global concern. To examine the impact of extreme weather events on blooms, eutrophication-related parameters (e.g., water temperature, nitrate, ammonium, nitrite, and soluble reactive phosphate (SRP)) were quantitatively assessed monthly over three years (2017–2019) at Lake Seeburg (Central Germany), a shallow eutrophic lake with regular cyanobacterial blooms. In addition, SRP concentrations in sediment pore water were assessed monthly for one year (2018). The monitoring period included a three-day extremely heavy rain event in 2017 as well as a severe drought in summer 2018. No such extreme weather conditions occurred in 2019. After the heavy rain event in 2017, anoxic water containing high levels of ammonium and SRP entered the lake from flooded upstream wetlands. This external nutrient spike resulted in a heavy but short (3 weeks) and monospecific cyanobacterial bloom. A different situation occurred during the exceptionally hot and dry summer of 2018. Especially favored by high water temperatures, SRP concentrations in sediment pore waters gradually increased to extreme levels (34.4 mg/L). This resulted in a strong and sustained internal SRP delivery into the water column (69 mg/m2·d−1), which supported the longest-lasting cyanobacterial bloom (3 months) within the three-year monitoring period. Subsequent biomass decay led to oxygen-depleted conditions in the bottom waters, elevated ammonium, and, later, nitrate concentrations. Our observations demonstrate the particular effects of extreme weather events on nutrient dynamics and the phytoplankton composition in the lake. As the frequency and intensity of such events will likely increase due to climate change, their impacts need to be increasingly considered, e.g., in future remediation strategies."],["dc.description.sponsorship","The Nature Conservation Authority of Göttingen County"],["dc.description.sponsorship","Open-Access-Publikationsfonds 2022"],["dc.identifier.doi","10.3390/w14132032"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/111705"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/112433"],["dc.language.iso","en"],["dc.relation.eissn","2073-4441"],["dc.relation.issn","2073-4441"],["dc.relation.orgunit","Abteilung Geobiologie"],["dc.rights","CC BY 4.0"],["dc.title","Effects of Weather Extremes on the Nutrient Dynamics of a Shallow Eutrophic Lake as Observed during a Three-Year Monitoring Study"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.subtype","original_ja"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","18"],["dc.bibliographiccitation.journal","Journal of Palaeogeography"],["dc.bibliographiccitation.volume","8"],["dc.contributor.author","Zeng, Ling-Qi"],["dc.contributor.author","Yi, Hai-Sheng"],["dc.contributor.author","Xia, Guo-Qing"],["dc.contributor.author","Simon, Klaus"],["dc.contributor.author","Heim, Christine"],["dc.contributor.author","Arp, Gernot"],["dc.date.accessioned","2019-07-09T11:51:14Z"],["dc.date.available","2019-07-09T11:51:14Z"],["dc.date.issued","2019"],["dc.description.abstract","Lacustrine stromatolites were widespread in the Miocene Wudaoliang Group (stromatolites of the Wudaoliang Group), northern Tibetan Plateau; but only at one location nearby the Wudaoliang Town, they occurred intensively in thick, laterally traceable beds (Wudaoliang stromatolites). Although deposited in lacustrine environment, the lack of fossils in these rocks hampers determining whether the stromatolites formed in freshwater or saline conditions. To address this problem, and in an attempt to identify criteria to distinguish differences of freshwater and saline conditions, we studied the laminae microfabrics, stable carbon and oxygen isotope ratios, rare earth element patterns and biomarkers of the stromatolites. These stromatolites can be divided into fenestral stromatolites and agglutinated stromatolites. The fabric of fenestral stromatolites is formed by microcrystalline carbonate enclosing spar-cemented, angular crystal traces. Essentially, this fabric is interpreted as pseudomorph after former formed evaporite crystals. Faecal pellets identical to that of the present-day brine shrimp Artemia, lack of other eukaryotic fossils, and stable isotopic signals point to a shallow, evaporation-dominated hypersaline lake setting. Covariation of carbon and oxygen isotopes indicates hydrologically closed conditions of the Miocene lake on northern Tibetan Plateau. However, if compared to other lacustrine carbonates of the Wudaoliang Group, the high δ13C values of the investigated Wudaoliang stromatolites reveal an additional photosynthetic effect during the deposition of the stromatolites. Furthermore, although no direct evidence is available from field observations and microfabrics, a positive europium anomaly of Wudaoliang stromatolites indicates that a palaeo-hydrothermal inflow system had existed in the outcrop area. These new results favour a hypersaline lake setting subject to hot spring inflow for the Wudaoliang stromatolites, in contrast to earlier interpretations suggesting a freshwater lake setting (e.g. Yi et al., Journal of Mineralogy and Petrology 28: 106–113, 2008; Zeng et al., Journal of Mineralogy and Petrology 31: 111–119, 2011). This approach may be appropriate for other lacustrine, unfossiliferous microbialites in settings where the environmental conditions are difficult to determine."],["dc.identifier.doi","10.1186/s42501-019-0033-7"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/16083"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/59905"],["dc.language.iso","en"],["dc.notes.intern","Merged from goescholar"],["dc.relation.orgunit","Fakultät für Geowissenschaften und Geographie"],["dc.rights","CC BY 4.0"],["dc.rights.uri","https://creativecommons.org/licenses/by/4.0/"],["dc.title","Palaeoenvironmental setting of lacustrine stromatolites in the Miocene Wudaoliang Group, northern Tibetan Plateau"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]