Geobiology最新文献

{"title":"Membrane Vesicle Formation Removes Iron Sulfide Mineral Crusts From the Cell Surface of Growing Sulfate-Reducing Bacteria.","authors":"Cheyenne Brokaw, Patrice Boyd, Aude Picard","doi":"10.1111/gbi.70047","DOIUrl":"10.1111/gbi.70047","url":null,"abstract":"<p><p>Sulfate-reducing bacteria (SRB) drive the process of sulfate reduction in low-temperature sedimentary environments. Through the production of sulfide, they promote the formation of iron-sulfide (Fe-S) minerals when Fe(II) is available. The negative charge of the cell surface of bacteria can promote the binding of Fe(II), leading to the precipitation of Fe-S minerals at the surface of SRB when sulfide is released from cells. We evaluated interactions between Fe-S minerals and the surface of SRB using transmission electron microscopy (TEM) in cultures of Maridesulfovibrio hydrothermalis AM13 grown with 4 mM of Fe(II) over 1 month of incubation. On average, 18% ± 10% of cells were encrusted in cultures collected during the exponential phase. Fe-S mineral deposition occurred at the surface of cells while cells were growing and producing sulfide in the presence of Fe(II), but mineral crusts were removed from most cells shortly after deposition. Cells removed crusts from their surface through the formation of membrane vesicles, which were apparently only produced during growth. Mineralized and non-mineralized membrane vesicles were preserved in mineral aggregates in stationary-phase cultures. On average, 17% ± 7% of cells were encrusted in cultures collected during the stationary phase, indicating that Fe-S minerals precipitated during the exponential phase and removed from the cell surface did not aggregate back onto cells. On the contrary, they formed large aggregates away from cells. When Fe-S mineral precipitation occurred in non-growing cell suspensions that were first exposed to Fe(II) then to sulfide, the proportion of encrusted cells increased to 95% ± 6%, indicating that resting or non-growing cells were not able to remove mineral crusts from their surface. The metabolic status of SRB therefore plays a role in their ability to escape Fe-S mineral entombment.</p>","PeriodicalId":173,"journal":{"name":"Geobiology","volume":"24 3","pages":"e70047"},"PeriodicalIF":3.4,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13129620/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147758323","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":"Paleoenvironmental Stasis for the Bioturbating Community During the Paleocene-Eocene Thermal Maximum at the Southern Iberian Margin.","authors":"Olmo Miguez-Salas, Francisco J Rodríguez-Tovar, Victoriano Pujalte","doi":"10.1111/gbi.70048","DOIUrl":"https://doi.org/10.1111/gbi.70048","url":null,"abstract":"<p><p>During the Paleocene-Eocene Thermal Maximum (PETM), there was an increase in global temperatures and emissions of isotopically depleted carbon, resulting in a negative carbon isotope excursion (CIE). This climatic event caused a widespread ocean deoxygenation, leading to substantial biotic turnover. Previous ichnological studies of deep-sea environments have suggested that bioturbating communities perished or diminished considerably during this event. In this study, we present an ichnological analysis of a well-known deep-sea outcrop (Rio Gor section; lower bathyal-upper abyssal depth; 1000-2000 m) from the southern Iberian margin. Contrary to previous studies, at this location, the PETM onset did not result in the extinction of the bioturbating community. In fact, high abundances of trace fossils were recorded during the PETM, indicating favorable paleoenvironmental conditions for the community. We discuss how sedimentary and climatic dynamics played a key role in regulating trace fossil abundance throughout the PETM. The paleogeographical position and deep-water circulation of the area appear to have played a crucial role in preventing low-oxygen deep water masses and the impoverishment of the bioturbating community. Overall, our findings reveal the PETM's positive impact on the bioturbating community at the southern Iberian margin. Given the essential ecological functions of these organisms on the seafloor-such as nutrient recycling and sediment mixing-we emphasize their potential importance in future warmer ocean scenarios.</p>","PeriodicalId":173,"journal":{"name":"Geobiology","volume":"24 3","pages":"e70048"},"PeriodicalIF":3.4,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147863341","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":"Tricks of Nature From the Ancient Earth and Early Mars: Chemical Gardens Generate Biomorphs With High Preservation Potential.","authors":"Solomon Hirsch, Sean McMahon, Jens Najorka, Mark A Sephton","doi":"10.1111/gbi.70045","DOIUrl":"10.1111/gbi.70045","url":null,"abstract":"<p><p>Observations of morphology are commonly used to evaluate the biogenicity of terrestrial microfossils and could constitute a crucial line of evidence for extraterrestrial life-detection missions in the future. However, evaluating the origin of morphological features in the rock record can be problematic because naturally occurring abiotic structures can resemble biological morphologies, which may lead to false-positive detections of fossilised life. Iron-mineralised chemical gardens have been highlighted as potentially confounding abiotic structures because of their morphological and chemical resemblance to biomineralised filaments. Despite this, the potential for chemical garden structures to be preserved in the fossil record has not been thoroughly investigated. Here, we subjected abiotic iron-mineralised chemical garden structures to artificial maturation using hydrous pyrolysis, in order to evaluate their preservation potential. We found that these abiotic filaments were relatively resistant to degradation caused by maturation when compared with analogous biological material. Additionally, the transformation of ferrihydrite to crystalline iron oxides was found to be relatively inhibited, likely because of the influence of silica. These findings highlight the need for fossilised filamentous material to be distinguished from chemical garden structures before a biological origin can be confidently attributed, particularly when observed in significantly altered rocks.</p>","PeriodicalId":173,"journal":{"name":"Geobiology","volume":"24 2","pages":"e70045"},"PeriodicalIF":3.4,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13100049/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147758297","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":"Correction to “On the Trail of Iron Uptake in Ancestral Cyanobacteria on Early Earth”","authors":"","doi":"10.1111/gbi.70043","DOIUrl":"10.1111/gbi.70043","url":null,"abstract":"<p>Enzingmüller-Bleyl, T. C., J. S. Boden, A. J. Herrmann, K. W. Ebel, P. Sánchez-Baracaldo, N. Frankenberg-Dinkel, and M. M. Gehringer. 2022. “On the Trail of Iron Uptake in Ancestral Cyanobacteria on Early Earth.” <i>Geobiology</i> 20: 776–789. https://doi.org/10.1111/gbi.12515.</p><p>We apologize for this error.</p>","PeriodicalId":173,"journal":{"name":"Geobiology","volume":"24 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2026-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/gbi.70043","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146117108","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":"Phytochemical Screening of 45-Million-Year-Old Colored Angiosperm Leaves Reveals Distinctive Chlorophyll-Derived and Polyphenolic Pigments","authors":"Klaus Wolkenstein,&nbsp;Christa E. Müller,&nbsp;Marianne Engeser,&nbsp;Holm Frauendorf,&nbsp;Victoria E. McCoy,&nbsp;Carole T. Gee","doi":"10.1111/gbi.70042","DOIUrl":"10.1111/gbi.70042","url":null,"abstract":"<p>Present-day angiosperm plants produce a plethora of metabolites including pigments that serve for important functions such as photosynthesis, protection against light, attraction of pollinators, and defense against microbes and herbivores. However, little is known about phytochemical constituents of ancient angiosperms, their distribution in the fossil record, their stability in deep time, and diagenesis. Outstanding preservation of ancient angiosperms, including exceptional color preservation, has been reported, but chemical analyses of such valuable specimens are limited by the rarity of the fossil material and the small amounts of potentially preserved metabolites. Here we use highly sensitive targeted liquid chromatography–tandem mass spectrometry in multiple reaction monitoring mode to screen for nanogram quantities of intact ancient phytochemical metabolites and their products in exceptionally well-preserved, about 45-Ma-old leaves from the Eocene Geiseltal fossil Lagerstätte, Germany. We show that diverse chlorophyll derivatives and degradation products as well as polyphenolic pigments are preserved in green to yellow colored angiosperm leaves and the brown coal matrix from Geiseltal. Most interesting is the fossil occurrence of the “unstable” green chlorophyll derivative dihydro-13²,17³-cyclopheophorbide <i>a</i>-enol, since cyclopheophorbide-enols are otherwise known as unique non-fluorescent chlorophyll catabolites of microorganisms in modern aquatic environments. The monopyrrole hematinic acid is interpreted as a stable product of chlorophyll catabolism via linear tetrapyrroles. Moreover, polyphenolic compounds in the fossil angiosperms are represented by the flavonoid pigments apigenin and luteolin. Our results demonstrate the potential of paleometabolomic-like screening of individual plant fossils to trace the fate of phytochemical constituents and to understand the processes of fossilization at the molecular level.</p>","PeriodicalId":173,"journal":{"name":"Geobiology","volume":"24 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2026-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12860425/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146091734","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":"Localized and Transient Oxygenation of Shallow Oceans of Southwestern Laurentia at the Ediacaran–Cambrian Boundary","authors":"Watsawan Chanchai,&nbsp;Lyle L. Nelson,&nbsp;Emily F. Smith,&nbsp;Dalton S. Hardisty,&nbsp;Mary C. Lonsdale,&nbsp;Janet E. Burke,&nbsp;Kimberly V. Lau","doi":"10.1111/gbi.70039","DOIUrl":"10.1111/gbi.70039","url":null,"abstract":"<p>The Ediacaran–Cambrian boundary, which precedes one of the most significant biotic diversification events in Earth's history, is associated with a global negative carbon isotope excursion termed the BAsal Cambrian carbon isotope Excursion (BACE). Late Ediacaran and early Cambrian changes in shallow marine oxygenation have been proposed to relate to the BACE as well as metazoan extinction and radiation. However, reconstructing paleoredox conditions at the Ediacaran–Cambrian boundary is limited by challenges in correlating carbonate strata due to sparse stratigraphic markers and non-unique chemostratigraphic correlations. These imprecise correlations have led to uncertainty in how redox changes across the BACE should be interpreted in relation to broader regional and global environmental patterns. Here, we present redox reconstructions from southwestern Laurentian carbonate successions that record the BACE, including the limestone-dominated Deep Spring Formation, southwestern USA, and the dolostone-dominated La Ciénega Formation, northern Mexico. We combine local (carbonate-bound iodine, I/(Ca + Mg) and cerium anomaly, Ce/Ce*) and global (carbonate-associated uranium isotopes, δ²³⁸U_carb) redox proxies to investigate marine oxygenation in relation to the BACE. Contrary to previous suggestions that a global ocean oxygenation event coincided with the BACE, we do not observe a shift in δ²³⁸U_carb concurrent with the carbon isotope excursion in either section. The δ²³⁸U_carb values differ between two sections, likely reflecting distinct diagenetic offsets attributed to different diagenetic U reduction, but together provide a minimal constraint on the carbonate δ²³⁸U value and suggest a more anoxic ocean compared to today. The local proxy results at both sites suggest widespread low-oxygen surface waters with a transient and localized interval of shallow marine oxygenation at one site that coincides with the nadir of the BACE. Persistently low I/(Ca + Mg) ratios, below values observed in today's oxygenated oceans, suggest a broadly redox-stratified surface ocean. Negative Ce anomalies in the La Ciénega Formation were recorded during the BACE nadir, suggesting a short-lived interval of local oxygenation within otherwise low-oxygen conditions. In sum, we do not find evidence for major, widespread oxygenation coincident with the BACE, but a continuation of low-oxygen conditions punctuated by a short-lived oxygenation event in the shallow oceans. These brief fluctuations in oxygen levels, in turn, may have played a role in the onset of behavioral complexity among bilaterian invertebrates during this critical transition.</p>","PeriodicalId":173,"journal":{"name":"Geobiology","volume":"24 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12754582/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145861355","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":"Redox Dynamics of the Atmosphere and Oceans Induced by the Paleoproterozoic Snowball Earth Events","authors":"Mariko Harada,&nbsp;Yuna Miura,&nbsp;Yasuto Watanabe,&nbsp;Kazumi Ozaki","doi":"10.1111/gbi.70040","DOIUrl":"10.1111/gbi.70040","url":null,"abstract":"<p>The Paleoproterozoic Earth underwent profound environmental changes, including multiple severe glaciations and fluctuations in atmospheric oxygen (O₂) levels. However, the precise relationship between O₂ evolution and the glaciations remains unclear. Here, we use a biogeochemical cycle model involving carbon, phosphorus, sulfur, and oxygen to investigate the redox dynamics of the ocean—atmosphere system following the climatic transition to a super-greenhouse state after deglaciation. Our stochastic analysis reveals that climatic recovery on a timescale of ~10⁵ years from elevated atmospheric CO₂ levels (&gt; 0.2 atm) triggers an extensive oxidation of the atmosphere and oceans over the subsequent 10⁶–10⁷ years, aligning with the large sulfur isotope anomaly in buried pyrite after the third Paleoproterozoic glaciation (~2.3 Ga). This finding suggests that the third glaciation represented an extensively glaciated, snowball state, which would have required massive accumulation of atmospheric CO₂ for deglaciation. Variation in the boundary conditions regarding the global redox budget, as represented by high reductant fluxes, may explain the return of atmospheric O₂ to Archean-like levels following the first (Makganyene) glaciation, which is also considered a snowball Earth.</p>","PeriodicalId":173,"journal":{"name":"Geobiology","volume":"23 6","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12743051/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145843209","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":"A Comprehensive Study of Biohopanoid Production in Alphaproteobacteria: Biosynthetic, Chemotaxonomical, and Geobiological Implications","authors":"Jaap S. Sinninghe Damsté,&nbsp;Michel Koenen,&nbsp;Vera Thiel,&nbsp;Nora Richter,&nbsp;Ellen C. Hopmans,&nbsp;Nicole J. Bale","doi":"10.1111/gbi.70038","DOIUrl":"10.1111/gbi.70038","url":null,"abstract":"&lt;p&gt;Bacteriohopanepolyol derivatives (BHPDs) and dia- and catagenetic products formed from these bacterial membrane modifiers are extensively used as biomarkers in molecular ecological and geoscience studies. Some BHPDs can be assigned to specific phylogenetic bacterial groups. With the vastly increasing availability of complete bacterial genomes, hopanoid production can be readily predicted by the presence of specific genes encoding biosynthetic enzymes involved in their production, but the time-consuming physiological confirmation remains a critical element in the interpretation of such data in a biosynthetic and paleontological context. &lt;i&gt;Alphaproteobacteria&lt;/i&gt; (APB) have often been proposed as important BHPD producers in a wide variety of environments and produce indicative BHPDs containing an additional methyl group in the A-ring, complicating the assignment of 2-methyl hopanes to N&lt;sub&gt;2&lt;/sub&gt;-fixing cyanobacteria in paleontological studies. Here we provide the first comprehensive study of the relationship between genotype and phenotype with respect to the production of C&lt;sub&gt;30&lt;/sub&gt; hopanoids and BHPDs by APB. Genome analysis of &gt; 6000 reference genomes of APB revealed that ca. 23% possess the genetic capacity to produce BHPDs, which is substantially higher than for all bacteria. However, BHPD biosynthesis genes were unevenly distributed between taxonomic and phylogenetic groups and not consistently found in mono-phylogenetic clusters. To study the relationship of genotype and phenotype with respect to the production of BHPDs, we cultivated 52 strains (50 terrestrial and 2 marine species) of the three major orders of the APB: &lt;i&gt;Hyphomicrobiales&lt;/i&gt;, &lt;i&gt;Rhodospirillales&lt;/i&gt;, and &lt;i&gt;Sphingomonadales&lt;/i&gt;. These include species of 29 genera that have not previously been examined for BHPDs. Intact BHPDs were analyzed by UHPLC-MS&lt;sup&gt;n&lt;/sup&gt;, resulting in the identification of overall 63 different structures and a wide variety in BHPD distributions. These results were in line with those obtained from Rohmer degradation on intact cells, which were specifically used to accurately assess the degree of methylation at C-2 and C-3 of ring A of the BHPDs. This revealed a 1–2 orders of magnitude lower degree of methylation at C-2 of BHPDs than for tetrahymanol (which was detected in three species all belonging to the &lt;i&gt;Nitrobacteraceae&lt;/i&gt;) and C&lt;sub&gt;30&lt;/sub&gt; hopanoids, which has important implications for the interpretation of the molecular fossil record. Our results also showed that the presence of BHPD biosynthetic genes, often organized in a biosynthetic gene cluster, in all cases results in actual production of BHPDs. Thus, the presence of BHPD genes is a good predictor for the actual production of BHPDs. However, the presence of genes encoding proteins that result in methylation at C-2 and C-3 of BHPDs does not always lead to the production of methylated BHPDs, complicating the interpretation of the presence of the &lt;i&gt;hpnP&lt;/i&gt; and &lt;i&gt;hpnR&lt;/","PeriodicalId":173,"journal":{"name":"Geobiology","volume":"23 6","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12583986/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145436690","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":"Understanding Ferruginous Versus Euxinic Conditions by Simulating Microbial Conditions in Meromictic Lakes","authors":"Vanessa M. Hawkins,&nbsp;Cody S. Sheik,&nbsp;Sergei Katsev","doi":"10.1111/gbi.70037","DOIUrl":"https://doi.org/10.1111/gbi.70037","url":null,"abstract":"<p>Ferruginous (iron-rich) conditions have been prominent in oceans throughout the Earth's geologic history but now are reliably found only in a handful of permanently stratified lakes. Microbially mediated iron reduction in such anoxic environments competes with sulfate reduction, which promotes euxinic (sulfide-rich) conditions. Besides the shared demand for organic compounds, the competition is fostered by the produced hydrogen sulfide, which may reduce iron oxides abiotically or co-precipitate with dissolved iron as iron sulfides. Understanding why some environments develop ferruginous rather than euxinic conditions (or vice versa), as well as the attendant effects on methanogenic fermentation, is key to understanding both modern and ancient anoxic ecosystems. Here, we reproduce biogeochemical distributions in multiple anoxic, low-sulfate, meromictic lakes around the world using a biomass-explicit reaction-transport model with a fixed set of metabolism-specific microbial parameters. The results suggest that sulfate reduction and methanogenesis are ubiquitous even in iron-rich systems, and are reflected in microbial surveys. Ferruginous conditions typically develop for surface sulfate concentrations below ≃100 μM. Interestingly, there seems to be a dearth of stably stratified water bodies where sulfate concentrations can persist in the medium-sulfate range of several hundred μM. Rather, when sulfur burial into the sediments becomes iron limited, sulfate tends to accumulate in the water column to much higher (mM) concentrations. A similar mechanism could be suggested to have operated in the variably sulfidic and ferruginous water columns of early oceans. Model simulations also reveal the previously underappreciated role of physical transport in shaping biogeochemical distributions, as minor variations in mixing rates can lead to large variations in microbial abundances. Model applicability across multiple lakes points to an encouraging possibility that geochemical patterns in complex biogeochemical systems may be described from a small number of thermodynamic and kinetic principles using a minimum of fitting parameters.</p>","PeriodicalId":173,"journal":{"name":"Geobiology","volume":"23 5","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/gbi.70037","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145317800","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":"Biogeochemistry of an Iron- and Manganese-Rich Stratified Lake: Tasik Biru, Malaysia, as a Modern Model Habitat for the Ancient Ocean","authors":"Muammar Mansor,&nbsp;Andreas Kappler,&nbsp;Tomás Israel Grijalva Rodríguez,&nbsp;Samuel Lihan,&nbsp;Sergei Katsev","doi":"10.1111/gbi.70036","DOIUrl":"10.1111/gbi.70036","url":null,"abstract":"<p>Tasik Biru is a ~70 m-deep tropical lake in Malaysia, originating from a water-filled open pit mine. We investigated the biogeochemistry and microbial community of the lake as a modern model habitat to the stratified ancient ocean. We found that a sharp redoxcline exists at around 50 m depth, related to the decrease of O₂ and pH (7.2–6.8) going down into the monimolimnion. Despite being relatively sulfate-rich (~320 μM), only a slight decrease of sulfate (to ~240 μM) was observed coupled with an increase of dissolved sulfide to 4 μM, attributed to microbial sulfate reduction in the monimolimnion. Comparatively, dissolved Fe and total Mn rose to ~50 μM in the anoxic layer with an unusual 1:1 concentration ratio. Other nutrients (PO₄³⁻, Si) and trace metal(loid)s (As, Mo, Sb, Co, U, and V) depth profiles increased or decreased across the chemocline, indicating controls via cycling of redox-sensitive elements. Microbial community analysis based on 16S rRNA amplicon sequencing reflects various metabolisms, from aerobic metabolisms in the mixolimnion to putative nitrite-dependent methane oxidation (e.g., by <i>Methylomirabilis</i>) at the chemocline, to sulfate reduction, methanogenesis, and fermentation in the monimolimnion. Tasik Biru is not in steady-state, and its anoxic water is predicted to shift from being Fe/Mn-rich to sulfide-rich, perhaps lending it as a model habitat to investigate biogeochemical changes from the metal-rich Archean to the Proterozoic oceans with expanding zones of sulfide-rich margins. An overview of the current biogeochemical cycles in the lake is presented, and open questions regarding partial sulfate consumption, methane, and Mn cycling and mineralogical distribution are highlighted to guide future studies.</p>","PeriodicalId":173,"journal":{"name":"Geobiology","volume":"23 5","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12515063/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145273150","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}