Nicolette R. Meyer

Stanford University

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Joann M. Stock

California Institute of Technology

Myriam A.C. Kars

Kōchi University

Shijun Jiang

Hainan University

Diana P. Bojanova

University of Southern California

Florian Schubert

Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences

Lucie C. Pastor

Ifremer

Wei Xie

Hohai University

Christophe Y. Galerne

University of Bremen

Florian Neumann

Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences

Louise M.T. Koornneef

University of Plymouth

Cooperative Institutions

International Ocean Discovery Program

Planetary Science Institute

Texas A&M University

University of Bremen

Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences

Center for Scientific Research and Higher Education at Ensenada

California Institute of Technology

Centre National de la Recherche Scientifique

Universidad Nacional Autónoma de México

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IODP Expedition 385 Alkalinity and pH

Zenodo (CERN European Organization for Nuclear Research) (2021)

Andreas Teske Daniel Lizarralde Tobias W. Höfig Ivano W. Aiello Jeanine L. Ash

Alkalinity was determined by Gran titration with an autotitrator (Metrohm 794 basic Titrino) using 0.1 M HCl at 20 degrees C. Report includes alkalinity, correction factor (if applicable), and pH.

Alkalinity

10.5281/zenodo.7705335

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IODP Expedition 385 Salinity

Zenodo (CERN European Organization for Nuclear Research) (2021)

Andreas Teske Daniel Lizarralde Tobias W. Höfig Ivano W. Aiello Jeanine L. Ash

Salinity was measured on interstitial water (IW) samples using an optical refractometer.

10.5281/zenodo.7708650

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Sulphur cycling in a Neoarchaean microbial mat

Geobiology (2017)

Nicolette R. Meyer Aubrey L. Zerkle David A. Fike

Abstract Multiple sulphur (S) isotope ratios are powerful proxies to understand the complexity of S biogeochemical cycling through Deep Time. The disappearance of a sulphur mass‐independent fractionation (S‐ MIF ) signal in rocks <~2.4 Ga has been used to date a dramatic rise in atmospheric oxygen levels. However, intricacies of the S‐cycle before the Great Oxidation Event remain poorly understood. For example, the isotope composition of coeval atmospherically derived sulphur species is still debated. Furthermore, variation in Archaean pyrite δ 34 S values has been widely attributed to microbial sulphate reduction ( MSR ). While petrographic evidence for Archaean early‐diagenetic pyrite formation is common, textural evidence for the presence and distribution of MSR remains enigmatic. We combined detailed petrographic and in situ, high‐resolution multiple S‐isotope studies (δ 34 S and Δ 33 S) using secondary ion mass spectrometry ( SIMS ) to document the S‐isotope signatures of exceptionally well‐preserved, pyritised microbialites in shales from the ~2.65‐Ga Lokammona Formation, Ghaap Group, South Africa. The presence of MSR in this Neoarchaean microbial mat is supported by typical biogenic textures including wavy crinkled laminae, and early‐diagenetic pyrite containing <26‰ μm‐scale variations in δ 34 S and Δ 33 S = −0.21 ± 0.65‰ (±1σ). These large variations in δ 34 S values suggest Rayleigh distillation of a limited sulphate pool during high rates of MSR . Furthermore, we identified a second, morphologically distinct pyrite phase that precipitated after lithification, with δ 34 S = 8.36 ± 1.16‰ and Δ 33 S = 5.54 ± 1.53‰ (±1σ). We propose that the S‐ MIF signature of this secondary pyrite does not reflect contemporaneous atmospheric processes at the time of deposition; instead, it formed by the influx of later‐stage sulphur‐bearing fluids containing an inherited atmospheric S‐ MIF signal and/or from magnetic isotope effects during thermochemical sulphate reduction. These insights highlight the complementary nature of petrography and SIMS studies to resolve multigenerational pyrite formation pathways in the geological record.

Biogeochemical Cycle

Isotopic signature

10.1111/gbi.12227

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Citations (24)

Expedition 385 summary

Proceedings of the International Ocean Discovery Program. Expedition reports (2021)

Andreas Teske Daniel Lizarralde Tobias W. Höfig Ivano W. Aiello J.L. Ash

sands, but it confirmed the dominant influence of gravity-flow sedimentation processes southeast of the axial graben.The scientific outcomes of Expedition 385 will (1) revise long-held assumptions about the role of sill emplacement in subsurface carbon mobilization versus carbon retention, (2) comprehensively examine the subsurface biosphere of Guaymas Basin and its responses and adaptations to hydrothermal conditions, (3) redefine hydrothermal controls on authigenic mineral formation in sediments, and (4) yield new insights into the long term influence of sill-sediment interaction on sediments deposited at the earliest stages of seafloor spreading, that is, when spreading centers are proximal to a continental margin.The generally high quality and high degree of completeness of the shipboard data sets present opportunities for inter-and multidisciplinary collaborations during shore-based studies.In comparison to DSDP Leg 64 to Guaymas Basin in 1979, continuous availability of sophisticated drilling strategies (e.g., the advanced piston corer [APC] and halflength APC systems) and numerous analytical innovations greatly improved sample recovery and scientific yield, particularly in the areas of organic geochemistry and microbiology.For example, microbial metagenomics did not exist 40 y ago.However, these technical refinements do not change the fact that Expedition 385 in many respects builds on the foundations of understanding laid by Leg 64 drilling in Guaymas Basin.Atmosphere Ocean Off-axis venting Terrigenous sedimentation Axial venting Carbon injection into the atmosphere?Anaerobic oxidation of methane Organic-rich sediments Alteration aureole

10.14379/iodp.proc.385.101.2021

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Nitrogen isotope homogenization of dissolved ammonium with depth and 15N enrichment of ammonium during incorporation into expandable layer silicates in organic-rich marine sediment from Guaymas Basin, Gulf of California

Chemical Geology (2024)

Toshiro Yamanaka Arisa Sakamoto Kanon Kiyokawa Jaeguk Jo Yuji Onishi

Sedimentary nitrogen isotopic ratios are used as a proxy for ancient biogeochemical cycles on Earth's surface. It is generally accepted that sediment core tops record primary signatures because organic nitrogen (ON) is predominant in this part of the core. In contrast to such early to middle diagenetic stages, it is well known that heavier nitrogen isotope 15N tends to enrich the sedimentary and metamorphic rocks during latter diagenetic and metamorphic stages. However, there are some critical gaps in our understanding of nitrogen isotopic alteration associated with abiotic processes during early-middle diagenesis. In this study, we examined the isotope ratios of ammonium nitrogen in interstitial water (IW) and total nitrogen (TN), including exchangeable ammonium and mineral nitrogen, in the solid-phase of those associated organic-rich-sediment recovered by International Ocean Discovery Program (IODP) Expedition 385 cores drilled in the Guaymas Basin, Gulf of California, that contained ammonium-rich IW. The isotopic ratios (δ15N value) of TN were the most variable with depth compared to any other type of nitrogen. This variation can be interpreted as reflecting changes in the water mass environment in the basin caused by glacial–interglacial climate changes, which modifies the δ15N values of the marine primary producers. Thus, the δ15N value of TN is a proxy for environmental change in the basin, while each component of TN shows different trends. The δ15N values of IW and exchangeable ammonium did not exhibit significant changes with depth, but the latter values were about 3 ‰ enriched in 15N. This may be due to advective transport of solute into adjacent layers followed by the formation of an isotopic equilibrium between IW and exchangeable ammonium in the case of fast accumulation rate. The δ15N value of exchangeable ammonium was the highest among the other types of nitrogen with one exception, where the δ15N value of TN was the highest. The calculated δ15N values of ON based on mass balance were almost the same to those of associated TN in the shallow sediment layers (< 150 m below seafloor), but the difference in the δ15N values of TN and ON were significant in the deeper layers, where proportions of ON contents were <50%. In particular, in the layer where the δ15N value of TN was the highest, that of ON showed an even higher value and the difference reaches 3.5 ‰. The δ15N values of mineral nitrogen were similar to that of IW ammonium except the surface layers. Under such conditions, when δ15N value of TN is intermediate between those of mineral nitrogen and exchangeable ammonium, calculated δ15N value of ON is close to that of TN. On the other hand, if δ15N value of TN is out of the range between mineral nitrogen and exchangeable ammonium, it causes further difference in δ15N value of ON. It means that the fluctuation of δ15N values of TN is reduced relative to those of ON through depth. It has been considered that δ15N value of TN in sediment is similar to that of ON, and changes in the δ15N value of TN due to diagenesis are limited, but in such environment ON fluctuations over depth may be slightly underestimated.

Isotopes of nitrogen

Authigenic

Biogeochemical Cycle

δ15N

10.1016/j.chemgeo.2024.122203

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NanoSIMS sample preparation decreases isotope enrichment: magnitude, variability and implications for single‐cell rates of microbial activity

Environmental Microbiology (2020)

Nicolette R. Meyer Julian L. Fortney Anne Dekas

Summary The activity of individual microorganisms can be measured within environmental samples by detecting uptake of isotope‐labelled substrates using nano‐scale secondary ion mass spectrometry (nanoSIMS). Recent studies have demonstrated that sample preparation can decrease 13 C and 15 N enrichment in bacterial cells, resulting in underestimates of activity. Here, we explore this effect with a variety of preparation types, microbial lineages and isotope labels to determine its consistency and therefore potential for correction. Specifically, we investigated the impact of different protocols for fixation, nucleic acid staining and catalysed reporter deposition fluorescence in situ hybridization (CARD‐FISH) on >14 500 archaeal and bacterial cells ( Methanosarcina acetivorans , Sulfolobus acidocaldarius and Pseudomonas putida ) enriched in 13 C, 15 N, 18 O, 2 H and/or 34 S. We found these methods decrease isotope enrichments by up to 80% – much more than previously reported – and that the effect varies by taxa, growth phase, isotope label and applied protocol. We make recommendations for how to account for this effect experimentally and analytically. We also re‐evaluate published nanoSIMS datasets and revise estimated microbial turnover times in the marine subsurface and nitrogen fixation rates in pelagic unicellular cyanobacteria. When sample preparation is accounted for, cell‐specific rates increase and are more consistent with modelled and bulk rates.

Stable-isotope probing

Pseudomonas putida

Biogeochemical Cycle

Isotopes of nitrogen

Isotopic labeling

10.1111/1462-2920.15264

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Heat flow and thermal regime in the Guaymas Basin, Gulf of California: Estimates of conductive and advective heat transport

Basin Research (2023)

Florian Neumann Raquel Negrete‐Aranda Robert N. Harris Juan Contreras Christophe Y. Galerne

Abstract Heat flow is estimated at eight sites drilled int the Guaymas Basin, Gulf of California, during the International Ocean Discovery Program Expedition 385. The expedition sought to understand the thermal regime of the basin and heat transfer between off‐axis sills intruding the organic‐rich sediments of the Guaymas Basin, and the basin floor. The distinct sedimentation rates, active tectonics, and magmatism make the basin interesting for scientific discoveries. Results show that sedimentation corrected heat flow values range 119–221 mW/m 2 in the basin and 257–1003 mW/m 2 at the site of a young sill intrusion, denominated Ringvent. Thermal analysis shows that heat in the Guaymas Basin is being dissipated by conduction for plate ages >0.2 Ma, whereas younger plate ages are in a state of transient cooling by both conduction and advection. Drilling sites show that Ringvent is an active sill being cooled down slowly by circulating fluids with discharge velocities of 10–200 mm/yr. Possible recharge sites are located ca. 1 km away from the sill's border. Modelling of the heat output at Ringvent indicates a sill thickness of ca. 240 m. A simple order‐of‐magnitude model predicts that relatively small amounts of magma are needed to account for the elevated heat flow in non‐volcanic, sediment‐filled rifts like the central and northern Gulf of California in which heating of the upper crust is achieved via advection by sill emplacement and hydrothermal circulation. Multiple timescales of cooling control the crustal, chemical and biological evolution of the Guaymas Basin. Here, we recognize at least four timescales: the time interval between intrusions (ca. 10 3 yr), the thermal relaxation time of sills (ca. 10 4 yr), the characteristic cooling time of the sediments (ca. 10 5 yr), and the cooling of the entire crust at geologic timescales.

Sill

Canada Basin

10.1111/bre.12755

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Expedition 385 methods

Proceedings of the International Ocean Discovery Program. Expedition reports (2021)

Andreas Teske Daniel Lizarralde Tobias W. Höfig Ivano W. Aiello Jeanine L. Ash

10.14379/iodp.proc.385.102.2021

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Rates and physicochemical drivers of microbial anabolic activity in deep‐sea sediments and implications for deep time

Environmental Microbiology (2022)

Nicolette R. Meyer Alma E. Parada Bennett J. Kapili Julian L. Fortney Anne Dekas

Abstract Sediment microorganisms influence global climate and redox by altering rates of organic carbon burial. However, the activity and ecology of benthic microorganisms are poorly characterized, especially in the deep sea. Here, we conducted nearly 300 stable isotope tracer experiments in sediments from the Pacific and Atlantic oceans (100–4500 m water depth) to determine the rates, spatial distribution, and physicochemical controls on microbial total anabolic activity, nitrogen fixation, and inorganic/organic carbon uptake. Using correlative and manipulative approaches, we find that total activity is limited primarily by organic carbon and/or energy. Activity correlates significantly with distance from shore, sediment depth, C:N ratios, and overlying chlorophyll concentrations and is stimulated by carbon but not nitrogen additions. Consistent with this, nitrogen fixation was undetected despite relatively low concentrations of porewater ammonium and the previous detection of nifH genes. Inorganic carbon uptake accounted for 7%–55% of carbon assimilation per sample (median 21%), suggesting chemoautotrophy is an important and unappreciated source of labile carbon in deep‐sea sediments. Community 16S rRNA was dominated by Bacteria (<2% Archaea), primarily Desulfobacterales of the Deltaproteobacteria. Leveraging our findings, we modelled global benthic microbial activity through geologic time and find the potential for significant shifts in total activity with supercontinental cycles.

Microbial mat

Nitrogen Cycle

Biogeochemical Cycle

Biogeochemistry

Carbon fixation

10.1111/1462-2920.16183

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IODP Expedition 385 Micropaleontology

Zenodo (CERN European Organization for Nuclear Research) (2021)

Andreas Teske Daniel Lizarralde Tobias W. Höfig Ivano W. Aiello Jeanine L. Ash

Paleontological data were collected using microscopes and recorded in the JRSO description software. All data for a species group (e.g., diatoms or nannofossils) were collected in a Microsoft Excel worksheet by hole. A zip file of the entire expedition's observations is also available.

Micropaleontology

10.5281/zenodo.7708672

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