Geobiology最新文献

{"title":"A 1 Ma sedimentary ancient DNA (sedaDNA) record of catchment vegetation changes and the developmental history of tropical Lake Towuti (Sulawesi, Indonesia)","authors":"Md Akhtar-E Ekram,&nbsp;Matthew Campbell,&nbsp;Sureyya H. Kose,&nbsp;Chloe Plet,&nbsp;Rebecca Hamilton,&nbsp;Satria Bijaksana,&nbsp;Kliti Grice,&nbsp;James Russell,&nbsp;Janelle Stevenson,&nbsp;Hendrik Vogel,&nbsp;Marco J. L. Coolen","doi":"10.1111/gbi.12599","DOIUrl":"10.1111/gbi.12599","url":null,"abstract":"<p>Studying past ecosystems from ancient environmental DNA preserved in lake sediments (<i>sed</i>aDNA) is a rapidly expanding field. This research has mainly involved Holocene sediments from lakes in cool climates, with little known about the suitability of <i>sed</i>aDNA to reconstruct substantially older ecosystems in the warm tropics. Here, we report the successful recovery of chloroplast <i>trn</i>L (UAA) sequences (<i>trn</i>L-P6 loop) from the sedimentary record of Lake Towuti (Sulawesi, Indonesia) to elucidate changes in regional tropical vegetation assemblages during the lake's Late Quaternary paleodepositional history. After the stringent removal of contaminants and sequence artifacts, taxonomic assignment of the remaining genuine <i>trn</i>L-P6 reads showed that native nitrogen-fixing legumes, C₃ grasses, and shallow wetland vegetation (<i>Alocasia</i>) were most strongly associated with &gt;1-million-year-old (&gt;1 Ma) peats and silts (114–98.8 m composite depth; mcd), which were deposited in a landscape of active river channels, shallow lakes, and peat-swamps. A statistically significant shift toward partly submerged shoreline vegetation that was likely rooted in anoxic muddy soils (i.e., peatland forest trees and wetland C₃ grasses (Oryzaceae) and nutrient-demanding aquatic herbs (presumably <i>Oenanthe javanica</i>)) occurred at 76 mcd (~0.8 Ma), ~0.2 Ma after the transition into a permanent lake. This wetland vegetation was most strongly associated with diatom ooze (46–37 mcd), thought to be deposited during maximum nutrient availability and primary productivity. Herbs (Brassicaceae), trees/shrubs (Fabaceae and Theaceae), and C₃ grasses correlated with inorganic parameters, indicating increased drainage of ultramafic sediments and laterite soils from the lakes' catchment, particularly at times of inferred drying. Downcore variability in <i>trn</i>L-P6 from tropical forest trees (<i>Toona</i>), shady ground cover herbs (Zingiberaceae), and tree orchids (<i>Luisia</i>) most strongly correlated with sediments of a predominantly felsic signature considered to be originating from the catchment of the Loeha River draining into Lake Towuti during wetter climate conditions. However, the co-correlation with dry climate-adapted trees (i.e., <i>Castanopsis</i> or <i>Lithocarpus</i>) plus C₄ grasses suggests that increased precipitation seasonality also contributed to the increased drainage of felsic Loeha River sediments. This multiproxy approach shows that despite elevated in situ temperatures, tropical lake sediments potentially comprise long-term archives of ancient environmental DNA for reconstructing ecosystems, which warrants further exploration.</p>","PeriodicalId":173,"journal":{"name":"Geobiology","volume":"22 3","pages":""},"PeriodicalIF":3.7,"publicationDate":"2024-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/gbi.12599","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140920769","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Energy flux couples sulfur isotope fractionation to proteomic and metabolite profiles in Desulfovibrio vulgaris","authors":"William D. Leavitt,&nbsp;Jacob Waldbauer,&nbsp;Sofia S. Venceslau,&nbsp;Min Sub Sim,&nbsp;Lichun Zhang,&nbsp;Flavia Jaquelina Boidi,&nbsp;Sydney Plummer,&nbsp;Julia M. Diaz,&nbsp;Inês A. C. Pereira,&nbsp;Alexander S. Bradley","doi":"10.1111/gbi.12600","DOIUrl":"10.1111/gbi.12600","url":null,"abstract":"<p>Microbial sulfate reduction is central to the global carbon cycle and the redox evolution of Earth's surface. Tracking the activity of sulfate reducing microorganisms over space and time relies on a nuanced understanding of stable sulfur isotope fractionation in the context of the biochemical machinery of the metabolism. Here, we link the magnitude of stable sulfur isotopic fractionation to proteomic and metabolite profiles under different cellular energetic regimes. When energy availability is limited, cell-specific sulfate respiration rates and net sulfur isotope fractionation inversely covary. Beyond net S isotope fractionation values, we also quantified shifts in protein expression, abundances and isotopic composition of intracellular S metabolites, and lipid structures and lipid/water H isotope fractionation values. These coupled approaches reveal which protein abundances shift directly as a function of energy flux, those that vary minimally, and those that may vary independent of energy flux and likely do not contribute to shifts in S-isotope fractionation. By coupling the bulk S-isotope observations with quantitative proteomics, we provide novel constraints for metabolic isotope models. Together, these results lay the foundation for more predictive metabolic fractionation models, alongside interpretations of environmental sulfur and sulfate reducer lipid-H isotope data.</p>","PeriodicalId":173,"journal":{"name":"Geobiology","volume":"22 3","pages":""},"PeriodicalIF":3.7,"publicationDate":"2024-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/gbi.12600","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140896810","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Interpreting an Archaean paleoenvironment through 3D imagery of microbialites","authors":"Cecilia M. Howard,&nbsp;Nathan D. Sheldon,&nbsp;Selena Y. Smith,&nbsp;Nora Noffke","doi":"10.1111/gbi.12601","DOIUrl":"10.1111/gbi.12601","url":null,"abstract":"<p>While stromatolites, and to a lesser extent thrombolites, have been extensively studied in order to unravel Precambrian (&gt;539 Ma) biological evolution, studies of clastic-dominated microbially induced sedimentary structures (MISS) are relatively scarce. The lack of a consolidated record of clastic microbialites creates questions about how much (and what) information on depositional and taphonomic settings can be gleaned from these fossils. We used μCT scanning, a non-destructive X-ray-based 3D imaging method, to reconstruct morphologies of ancient MISS and mat textures in two previously described coastal Archaean samples from the ~3.48 Ga Dresser Formation, Pilbara, Western Australia. The aim of this study was to test the ability of μCT scanning to visualize and make 3D measurements that can be used to interpret the biotic–environmental interactions. Fossil MISS including mat laminae with carpet-like textures in one sample and mat rip-up chips in the second sample were investigated. Compiled δ¹³C and δ³⁴S analyses of specimens from the Dresser Fm. are consistent with a taxonomically diverse community that could be capable of forming such MISS. 3D measurements of fossil microbial mat chips indicate significant biostabilization and suggest formation in flow velocities &gt;25 cm s⁻¹. Given the stratigraphic location of these chips in a low-flow lagoonal layer, we conclude that these chips formed due to tidal influence, as these assumed velocities are consistent with recent modeling of Archaean tides. The success of μCT scanning in documenting these microbialite features validates this technique both as a first step analysis for rare samples prior to the use of more destructive techniques and as a valuable tool for gaining insight into microbialite taphonomy.</p>","PeriodicalId":173,"journal":{"name":"Geobiology","volume":"22 3","pages":""},"PeriodicalIF":3.7,"publicationDate":"2024-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/gbi.12601","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140896813","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Deep-water first occurrences of Ediacara biota prior to the Shuram carbon isotope excursion in the Wernecke Mountains, Yukon, Canada","authors":"Thomas H. Boag,&nbsp;James F. Busch,&nbsp;Jared T. Gooley,&nbsp;Justin V. Strauss,&nbsp;Erik A. Sperling","doi":"10.1111/gbi.12597","DOIUrl":"https://doi.org/10.1111/gbi.12597","url":null,"abstract":"<p>Ediacara-type macrofossils appear as early as ~575 Ma in deep-water facies of the Drook Formation of the Avalon Peninsula, Newfoundland, and the Nadaleen Formation of Yukon and Northwest Territories, Canada. Our ability to assess whether a deep-water origination of the Ediacara biota is a genuine reflection of evolutionary succession, an artifact of an incomplete stratigraphic record, or a bathymetrically controlled biotope is limited by a lack of geochronological constraints and detailed shelf-to-slope transects of Ediacaran continental margins. The Ediacaran Rackla Group of the Wernecke Mountains, NW Canada, represents an ideal shelf-to-slope depositional system to understand the spatiotemporal and environmental context of Ediacara-type organisms' stratigraphic occurrence. New sedimentological and paleontological data presented herein from the Wernecke Mountains establish a stratigraphic framework relating shelfal strata in the Goz/Corn Creek area to lower slope deposits in the Nadaleen River area. We report new discoveries of numerous <i>Aspidella</i> hold-fast discs, indicative of frondose Ediacara organisms, from deep-water slope deposits of the Nadaleen Formation stratigraphically below the Shuram carbon isotope excursion (CIE) in the Nadaleen River area. Such fossils are notably absent in coeval shallow-water strata in the Goz/Corn Creek region despite appropriate facies for potential preservation. The presence of pre-Shuram CIE Ediacara-type fossils occurring only in deep-water facies within a basin that has equivalent well-preserved shallow-water facies provides the first stratigraphic paleobiological support for a deep-water origination of the Ediacara biota. In contrast, new occurrences of Ediacara-type fossils (including juvenile fronds, <i>Beltanelliformis</i>, <i>Aspidella</i>, annulated tubes, and multiple ichnotaxa) are found above the Shuram CIE in both deep- and shallow-water deposits of the Blueflower Formation. Given existing age constraints on the Shuram CIE, it appears that Ediacaran organisms may have originated in the deeper ocean and lived there for up to ~15 million years before migrating into shelfal environments in the terminal Ediacaran. This indicates unique ecophysiological constraints likely shaped the initial habitat preference and later environmental expansion of the Ediacara biota.</p>","PeriodicalId":173,"journal":{"name":"Geobiology","volume":"22 3","pages":""},"PeriodicalIF":3.7,"publicationDate":"2024-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140820651","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The paleoredox context of early eukaryotic evolution: insights from the Tonian Mackenzie Mountains Supergroup, Canada","authors":"Katie M. Maloney,&nbsp;Galen P. Halverson,&nbsp;Maxwell Lechte,&nbsp;Timothy M. Gibson,&nbsp;Thi Hao Bui,&nbsp;James D. Schiffbauer,&nbsp;Marc Laflamme","doi":"10.1111/gbi.12598","DOIUrl":"https://doi.org/10.1111/gbi.12598","url":null,"abstract":"<p>Tonian (ca. 1000–720 Ma) marine environments are hypothesised to have experienced major redox changes coinciding with the evolution and diversification of multicellular eukaryotes. In particular, the earliest Tonian stratigraphic record features the colonisation of benthic habitats by multicellular macroscopic algae, which would have been powerful ecosystem engineers that contributed to the oxygenation of the oceans and the reorganisation of biogeochemical cycles. However, the paleoredox context of this expansion of macroalgal habitats in Tonian nearshore marine environments remains uncertain due to limited well-preserved fossils and stratigraphy. As such, the interdependent relationship between early complex life and ocean redox state is unclear. An assemblage of macrofossils including the chlorophyte macroalga <i>Archaeochaeta guncho</i> was recently discovered in the lower Mackenzie Mountains Supergroup in Yukon (Canada), which archives marine sedimentation from ca. 950–775 Ma, permitting investigation into environmental evolution coincident with eukaryotic ecosystem evolution and expansion. Here we present multi-proxy geochemical data from the lower Mackenzie Mountains Supergroup to constrain the paleoredox environment within which these large benthic macroalgae thrived. Two transects show evidence for basin-wide anoxic (ferruginous) oceanic conditions (i.e., high Fe_HR/Fe_T, low Fe_py/Fe_HR), with muted redox-sensitive trace metal enrichments and possible seasonal variability. However, the weathering of sulfide minerals in the studied samples may obscure geochemical signatures of euxinic conditions. These results suggest that macroalgae colonized shallow environments in an ocean that remained dominantly anoxic with limited evidence for oxygenation until ca. 850 Ma. Collectively, these geochemical results provide novel insights into the environmental conditions surrounding the evolution and expansion of benthic macroalgae and the eventual dominance of oxygenated oceanic conditions required for the later emergence of animals.</p>","PeriodicalId":173,"journal":{"name":"Geobiology","volume":"22 3","pages":""},"PeriodicalIF":3.7,"publicationDate":"2024-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/gbi.12598","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140820649","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Origin and modern microbial ecology of secondary mineral deposits in Lehman Caves, Great Basin National Park, NV, USA","authors":"Zoë E. Havlena,&nbsp;Louise D. Hose,&nbsp;Harvey R. DuChene,&nbsp;Gretchen M. Baker,&nbsp;J. Douglas Powell,&nbsp;Amanda L. Labrado,&nbsp;Benjamin Brunner,&nbsp;Daniel S. Jones","doi":"10.1111/gbi.12594","DOIUrl":"https://doi.org/10.1111/gbi.12594","url":null,"abstract":"<p>Lehman Caves is an extensively decorated high desert cave that represents one of the main tourist attractions in Great Basin National Park, Nevada. Although traditionally considered a water table cave, recent studies identified abundant speleogenetic features consistent with a hypogenic and, potentially, sulfuric acid origin. Here, we characterized white mineral deposits in the Gypsum Annex (GA) passage to determine whether these secondary deposits represent biogenic minerals formed during sulfuric acid corrosion and explored microbial communities associated with these and other mineral deposits throughout the cave. Powder X-ray diffraction (pXRD), scanning electron microscopy with electron dispersive spectroscopy (SEM-EDS), and electron microprobe analyses (EPMA) showed that, while most white mineral deposits from the GA contain gypsum, they also contain abundant calcite, silica, and other phases. Gypsum and carbonate-associated sulfate isotopic values of these deposits are variable, with δ³⁴S_V-CDT between +9.7‰ and +26.1‰, and do not reflect depleted values typically associated with replacement gypsum formed during sulfuric acid speleogenesis. Petrographic observations show that the sulfates likely co-precipitated with carbonate and SiO₂ phases. Taken together, these data suggest that the deposits resulted from later-stage meteoric events and not during an initial episode of sulfuric acid speleogenesis. Most sedimentary and mineral deposits in Lehman Caves have very low microbial biomass, with the exception of select areas along the main tour route that have been impacted by tourist traffic. High-throughput 16S rRNA gene amplicon sequencing showed that microbial communities in GA sediments are distinct from those in other parts of the cave. The microbial communities that inhabit these oligotrophic secondary mineral deposits include OTUs related to known ammonia-oxidizing <i>Nitrosococcales</i> and Thaumarchaeota, as well as common soil taxa such as Acidobacteriota and Proteobacteria. This study reveals microbial and mineralogical diversity in a previously understudied cave and expands our understanding of the geomicrobiology of desert hypogene cave systems.</p>","PeriodicalId":173,"journal":{"name":"Geobiology","volume":"22 3","pages":""},"PeriodicalIF":3.7,"publicationDate":"2024-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140820650","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evaluating the multiple sulfur isotope signature of Eoarchean rocks from the Isua Supracrustal Belt (Southwest-Greenland) by MC-ICP-MS: Volcanic nutrient sources for early life","authors":"Jane E. Macdonald,&nbsp;Patrick Sugden,&nbsp;Matthew Dumont,&nbsp;Kristoffer Szilas,&nbsp;Stijn Glorie,&nbsp;Alexander Simpson,&nbsp;Sarah Gilbert,&nbsp;Andrea Burke,&nbsp;Eva E. Stüeken","doi":"10.1111/gbi.12595","DOIUrl":"https://doi.org/10.1111/gbi.12595","url":null,"abstract":"<p>On the anoxic Archean Earth, prior to the onset of oxidative weathering, electron acceptors were relatively scarce, perhaps limiting microbial productivity. An important metabolite may have been sulfate produced during the photolysis of volcanogenic SO₂ gas. Multiple sulfur isotope data can be used to track this sulfur source, and indeed this record indicates SO₂ photolysis dating back to at least 3.7 Ga, that is, as far back as proposed evidence of life on Earth. However, measurements of multiple sulfur isotopes in some key strata from that time can be challenging due to low sulfur concentrations. Some studies have overcome this challenge with NanoSIMS or optimized gas-source mass spectrometry techniques, but those instruments are not readily accessible. Here, we applied an <i>aqua regia</i> leaching protocol to extract small amounts of sulfur from whole rocks for analyses of multiple sulfur isotopes by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). Measurements of standards and replicates demonstrate good precision and accuracy. We applied this technique to meta-sedimentary rocks with putative biosignatures from the Eoarchean Isua Supracrustal Belt (ISB, &gt;3.7 Ga) and found positive ∆³³S (1.40–1.80‰) in four meta-turbidites and negative ∆³³S (−0.80‰ and −0.66‰) in two meta-carbonates. Two meta-basalts do not display significant mass-independent fractionation (MIF, −0.01‰ and 0.16‰). In situ Re–Os dating on a molybdenite vein hosted in the meta-turbidites identifies an early ca. 3.7 Ga hydrothermal phase, and in situ Rb–Sr dating of micas in the meta-carbonates suggests metamorphism affected the rocks at ca. 2.2 and 1.7 Ga. We discuss alteration mechanisms and conclude that there is most likely a primary MIF-bearing phase in these meta-sediments. Our new method is therefore a useful addition to the geochemical toolbox, and it confirms that organisms at that time, if present, may indeed have been fed by volcanic nutrients.</p>","PeriodicalId":173,"journal":{"name":"Geobiology","volume":"22 2","pages":""},"PeriodicalIF":3.7,"publicationDate":"2024-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/gbi.12595","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140541167","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Calcium isotope fractionation by intracellular amorphous calcium carbonate (ACC) forming cyanobacteria","authors":"Neha Mehta,&nbsp;Harold Bradbury,&nbsp;Karim Benzerara","doi":"10.1111/gbi.12596","DOIUrl":"https://doi.org/10.1111/gbi.12596","url":null,"abstract":"<p>The formation of intracellular amorphous calcium carbonate (ACC) by various cyanobacteria is a widespread biomineralization process, yet its mechanism and importance in past and modern environments remain to be fully comprehended. This study explores whether calcium (Ca) isotope fractionation, linked to ACC-forming cyanobacteria, can serve as a reliable tracer for detecting these microorganisms in modern and ancient settings. Accordingly, we measured stable Ca isotope fractionation during Ca uptake by the intracellular ACC-forming cyanobacterium <i>Cyanothece</i> sp. PCC 7425. Our results show that <i>Cyanothece</i> sp. PCC 7425 cells are enriched in lighter Ca isotopes relative to the solution. This finding is consistent with the kinetic isotope effects observed in the Ca isotope fractionation during biogenic carbonate formation by marine calcifying organisms. The Ca isotope composition of <i>Cyanothece</i> sp. PCC 7425 was accurately modeled using a Rayleigh fractionation model, resulting in a Ca isotope fractionation factor (Δ⁴⁴Ca) equal to −0.72 ± 0.05‰. Numerical modeling suggests that Ca uptake by these cyanobacteria is primarily unidirectional, with minimal back reaction observed over the duration of the experiment. Finally, we compared our Δ⁴⁴Ca values with those of other biotic and abiotic carbonates, revealing similarities with organisms that form biogenic calcite. These similarities raise questions about the effectiveness of using the Ca isotope fractionation factor as a univocal tracer of ACC-forming cyanobacteria in the environment. We propose that the use of Δ⁴⁴Ca in combination with other proposed tracers of ACC-forming cyanobacteria such as Ba and Sr isotope fractionation factors and/or elevated Ba/Ca and Sr/Ca ratios may provide a more reliable approach.</p>","PeriodicalId":173,"journal":{"name":"Geobiology","volume":"22 2","pages":""},"PeriodicalIF":3.7,"publicationDate":"2024-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/gbi.12596","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140537878","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Preserved particulate organic carbon is likely derived from the subsurface sulfidic photic zone of the Proterozoic Ocean: evidence from a modern, oxygen-deficient lake","authors":"Ashley B. Cohen,&nbsp;Lisa N. Christensen,&nbsp;Felix Weber,&nbsp;Milana Yagudaeva,&nbsp;Evan Lo,&nbsp;Gregory A. Henkes,&nbsp;Michael L. McCormick,&nbsp;Gordon T. Taylor","doi":"10.1111/gbi.12593","DOIUrl":"10.1111/gbi.12593","url":null,"abstract":"<p>Biological processes in the Proterozoic Ocean are often inferred from modern oxygen-deficient environments (MODEs) or from stable isotopes in preserved sediment. To date, few MODE studies have simultaneously quantified carbon fixation genes and attendant stable isotopic signatures. Consequently, how carbon isotope patterns reflect these pathways has not been thoroughly vetted. Addressing this, we profiled planktonic productivity and quantified carbon fixation pathway genes and associated organic carbon isotope values (δ¹³C_POC) of size-fractionated (0.2–2.7 and &gt;2.7 μm) particulate matter from meromictic Fayetteville Green Lake, NY, USA. The high-O₂ Calvin-Benson-Bassham (CBB) gene (<i>cbbL</i>) was most abundant in the &lt;2.7 μm size fraction in shallow oxic and deep hypoxic waters, corresponding with cyanobacterial and eukaryote algal populations. The low-O₂ CBB gene (<i>cbbM</i>) was most abundant near the lower oxycline boundary in the larger size fraction, coincident with purple sulfur bacteria populations. The reverse citric acid cycle gene (<i>aclB</i>) was equally abundant in both size fractions in the deepest photic zone, coinciding with green sulfur bacteria populations. Methane coenzyme reductase A (<i>mcrA</i>), of anaerobic methane cyclers, was most abundant at the lower oxycline boundary in both size fractions, coinciding with <i>Methanoregula</i> populations. δ¹³C_POC values overlapped with the high-O₂ CBB fixation range except for two negative excursions near the lower oxycline boundary, likely reflecting assimilation of isotopically-depleted groundwater-derived carbon by autotrophs and sulfate-reducers. Throughout aphotic waters, δ¹³C_POC values of the large size fraction became ¹³C-enriched, likely reflecting abundant purple sulfur bacterial aggregates. Eukaryote algae- or cyanobacteria-like isotopic signatures corresponded with increases in <i>cbbL</i>, <i>cbbM,</i> and <i>aclB</i>, and enrichment of exopolymer-rich prokaryotic photoautotrophs aggregates. Results suggest that δ¹³C_POC values of preserved sediments from areas of the Proterozoic Ocean with sulfidic photic zones may reflect a mixture of alternate carbon-fixing populations exported from the deep photic zone, challenging the paradigm that sedimentary stable carbon isotope values predominantly reflect oxygenic photosynthesis from surface waters.</p>","PeriodicalId":173,"journal":{"name":"Geobiology","volume":"22 2","pages":""},"PeriodicalIF":3.7,"publicationDate":"2024-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140108573","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Nubecularia-coralline algal-serpulid-microbial bioherms of the Paratethys Sea—Distribution and paleoecological significance (upper Serravallian, upper Sarmatian, Middle Miocene)","authors":"Werner E. Piller,&nbsp;Mathias Harzhauser","doi":"10.1111/gbi.12590","DOIUrl":"10.1111/gbi.12590","url":null,"abstract":"<p><i>Nubecularia</i> bioherms represent unique bioconstructions that are restricted to the upper Serravallian of the Paratethys and have been reported since the 19th century. They occur in the Central Paratethys in the late Sarmatian and the Eastern Paratethys in the Bessarabian both regional stages of the respective Paratethyan areas. In this study, several locations in the Vienna and Styrian basins of the Central Paratethys were studied out of which four localities were documented in detail (Wolfsthal, Maustrenk, St. Margarethen—Zollhaus, Vienna—Ruzickagasse) to reconstruct their sedimentary setting, their internal composition, and their indications of environmental parameters. The detailed studies included logging of outcrop sections, petrographic, facies and biotic analyses of polished slabs and thin sections and also cathodoluminescence analyses. These concluded that these bioconstructions are not only composed of the foraminifer <i>Nubecularia</i> but represent a complex mixture and interrelationships of <i>Nubecularia</i>, serpulids and microbial carbonate. Four boundstone types can be differentiated: <i>Nubecularia</i> boundstone, <i>Nubecularia</i>-coralline algal boundstone, stromatolitic/thrombolitic boundstone and serpulid-nubeculariid-microbial boundstone. The first 3 types are characteristic of specific localities; the fourth type occurs in all studied locations and represents the terminal association on top of the three other types. The three basal boundstones are predominantly of columnar growth form irrespective of dominance of <i>Nubecularia</i>, coralline algae or microbial carbonate, and the terminal boundstone is widely irregularly organized. The general depositional environment is characterized by cross-bedded oolitic grainstones with abundant quartz grains, miliolid foraminifers and mollusks. Intercalated are microbial carbonates mostly stromatolites but also thrombolites. This indicates a general high water energy environment interrupted by more calm periods when the microbial carbonate was built. The 3 basal types of bioconstructions are interpreted to reflect decreasing food supply and/or oxygenation from <i>Nubecularia</i> over <i>Nubecularia</i>-coralline algal to stromatolitic/thrombolitic boundstone. The serpulid-nubeculariid-microbial boundstone reflects an internal succession with a decrease of the same parameters. Water depth is considered very shallow ranging from 0 to a few meters, and salinity was normal marine to hypersaline. The reconstructed paleoenvironment with dominating oolite shoals and seagrass meadows was not restricted to the Central Paratethys but extended over the entire Paratethys and represented the largest oolite facies area of the entire Cenozoic!</p>","PeriodicalId":173,"journal":{"name":"Geobiology","volume":"22 2","pages":""},"PeriodicalIF":3.7,"publicationDate":"2024-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/gbi.12590","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140100598","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}