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            <gmx:Anchor xlink:href="http://lod.bco-dmo.org/id/dataset/991374.rdf" xlink:actuate="onRequest">Geochemical data supporting methanogenesis rates in subsurface sediments from R/V JOIDES Resolution IODP-385 drilling expedition in the Guaymas Basin between September and November, 2019</gmx:Anchor>
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            <gco:CharacterString>Cite this dataset as: Joye, S. B. (2025) Geochemical data supporting methanogenesis rates in subsurface sediments from R/V JOIDES Resolution IODP-385 drilling expedition in the Guaymas Basin between September and November, 2019. Biological and Chemical Oceanography Data Management Office (BCO-DMO). (Version 1) Version Date 2025-01-14 [if applicable, indicate subset used]. http://lod.bco-dmo.org/id/dataset/991374 [access date]</gco:CharacterString>
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        <gco:CharacterString>Guaymas Basin Leg 385 Geochemistry Associated with Methanogenesis Rates Dataset Description: &amp;lt;p&amp;gt;&amp;lt;strong&amp;gt;Study Results&amp;lt;/strong&amp;gt;&amp;lt;/p&amp;gt;

&amp;lt;p&amp;gt;Thermodynamic calculations and C1/C2+ ratios indicated that methane in the relatively cooler, shallower layers, was predominantly of biogenic origin. Radiotracer experiments provided direct evidence for the coexistence of multiple methanogenic pathways, hydrogenotrophic, acetoclastic, and methylotrophic, across the sediment column. Methanogenic activity from multiple methanogenic pathways occurred over a wide temperature range (3°C to 80°C), highlighting the unexpectedly high metabolic versatility of methanogens in deep, thermally heated sediments. High methanogenesis rates were detected in near-surface sediments driven predominantly by methylotrophic methanogenesis, followed by hydrogenotrophic pathways. However, these rates declined sharply with depth, particularly within the 40–60°C interval, indicating a transition from mesophilic to thermophilic microbial communities, due to rising temperatures, reductions in gene expression, and decreasing microbial cell densities. Methylotrophic methanogenesis remained detectable down to 320 meters below the seafloor and was the dominant methane-producing pathway at temperatures up to 60°C. In sediments increasingly influenced by sill intrusions, hydrogenotrophic and acetoclastic methanogenesis became the predominant modes of methane production.&amp;amp;nbsp;&amp;lt;/p&amp;gt;

&amp;lt;p&amp;gt;Methanogenic activity rates from multiple substrates at 80°C were comparable to rates in near-surface sediments. This deep, hot activity is attributed to the presence of active microbial biomass and the enhanced reactivity and bioavailability of organic matter in deep, hydrothermally-heated sediments, which provided abundant substrates for methanogenesis. These findings expand the current understanding of methanogenesis in the deep biosphere and reveal the discovery of the contemporaneous activity of multiple methanogenic pathways in deep, hydrothermally-influenced sediments.&amp;lt;/p&amp;gt;

&amp;lt;p&amp;gt;See related datasets for all data referenced in these findings.&amp;lt;/p&amp;gt; Methods and Sampling: &amp;lt;p&amp;gt;Subsurface sediment samples were collected from four drilling sites in the Guaymas Basin, Gulf of California, during IODP Expedition 385 “Guaymas Basin Tectonics and Biosphere” using the research vessel R/V JOIDES Resolution. Rates of methanogenesis were determined at four sites. Sites 1545 (27º38.230’N, 111º53.329’W) and 1546 (27º37.884’N, 111º52.781’W) were located roughly 52 km and 51 km, respectively, northwest of the axial graben of the northern spreading segment. Both sites are highly sedimented and a 75-meter thick inactive (~thermally equilibrated) basaltic/doleritic/gabbroic sill was present at site 1546 between ~355 to 431 meters below the seafloor (mbsf). Site U1545 is considered a reference site since it was free of sill intrusions and unaffected by active hydrothermal circulation. Samples to determine methanogenesis rates were collected from the &amp;quot;B&amp;quot; hole at every site (during IODP expeditions, several, closely-spaced holes are drilled at each site so that sufficient sediment is available for all of the proposed work.)&amp;lt;/p&amp;gt;

&amp;lt;p&amp;gt;The geothermal gradient at hole U1545B was 227ºC/km. The geothermal gradient at site U1546B was similar to that measured in hole U1545B, 221ºC/km, since the sill at 1546B was thermally equilibrated. Sites U1547 (27º30.413’N, 111º40.734’W) were located inside the periphery of an active, sill-associated hydrothermal mound located about 27 km northwest of the axial graben of the northern spreading segment. Temperatures in hole U1547B exceeded 50°C in the upper 50 mbsf. The geothermal gradient at this site was between 511ºC to 960ºC/km. Site U1549 was located near a cold seep sustained by a deeply buried, thermally equilibrated sill intrusion at several hundred meters depth. The geothermal gradient at hole U1549B was 194ºC/km.&amp;lt;/p&amp;gt;

&amp;lt;p&amp;gt;Sediment samples were collected using an advanced piston coring system (APC) and a half-length APC (Teske et al. 2021). After retrieval on deck, sediment cores were sectioned in a designated core cutting area. Approximately 0.5 cm of the outer sediment layer was carefully removed to minimize potential contamination. For analysis of hydrocarbon gases, ~ 5 mL sediment was transferred into 21.5 mL clean, pre-combusted glass vials using a cut-off syringe. The vials were sealed immediately with polytetrafluoroethylene septa and aluminum caps and were incubated for 30 min at 70°C to allow dissolved hydrocarbon gases to equilibrate with the headspace before analysis, as described in Teske et al. (2021).&amp;amp;nbsp;&amp;lt;/p&amp;gt;

&amp;lt;p&amp;gt;Data describing &amp;lt;em&amp;gt;in situ &amp;lt;/em&amp;gt;geochemistry and temperature were generated shipboard, as outlined in Teske et al. (2021). Porewater for geochemical analyses was extracted from subsurface sediments using a shipboard squeezing apparatus, following established protocols (Manheim and Sayles 1974, Teske et al. 2021). To prevent contamination, ~0.5 cm of the outer sediment was carefully removed prior to transferring 150–300 cm&amp;lt;sup&amp;gt;3&amp;lt;/sup&amp;gt; of uncontaminated interior material into a titanium squeezing vessel. The vessel was placed in a Carver hydraulic press (Manheim and Sayles 1974), and the expressed porewater was filtered immediately through a 0.2 µm polyethersulfone membrane. Filtrates were collected in HCl-washed syringes and subsampled into acid-cleaned high-density polyethylene vials for onboard determinations of sulfate and ammonium, with samples stored at 4 °C following fixation (acidification with trace metal grade nitric acid for sulfate and phenol solution for ammonium).&amp;lt;/p&amp;gt;

&amp;lt;p&amp;gt;Dissolved inorganic carbon (DIC) was collected into 2 mL glass vials and preserved with 10 µL of saturated HgCl&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; for shore-based analysis. For acetate analysis, 2 mL porewater subsamples were preserved immediately after collection and stored frozen at −20 °C in pre-combusted glass vials with Teflon-coated screw caps (Heuer et al. 2009). Samples for methanol and trimethylamine (TMA) measurements were transferred immediately into pre-combusted and N&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;-purged 20 mL glass vials that were sealed with gas-tight butyl rubber stoppers, stored at −80°C until analysis.&amp;lt;/p&amp;gt;

&amp;lt;p&amp;gt;Hydrocarbon gas analysis was performed by extracting about 5 mL of headspace gas from the 21.5 mL vials using a gas-tight syringe and directly injecting it into an Agilent 7890A gas chromatograph with a flame ionization detector (FID) (Teske et al. 2021). Sulfate concentrations were measured by ion chromatography using a Metrohm 850 Professional IC system (Murray et al. 2000, Teske et al. 2021). Ammonium concentrations were determined by a colorimetric method involving phenol diazotization followed by oxidation with bleach (Clorox) to produce a blue color, measured at 640 nm using a Cary Series 100 UV-Vis spectrophotometer (Agilent Technologies) (Solorzano 1969, Teske et al. 2021). Samples were diluted beforehand to keep ammonium below 1000 μM. Methanol and TMA (~5 mL) in porewater were simultaneously quantified using a purge and trap pre-treatment system coupled with a gas chromatograph (Jiang et al. 2024). An Agilent Technologies Inc. (USA) 8890 gas chromatograph equipped with a purge and trap system (Acrichi PTC, Beijing Juxin Zhuifeng Technology, Ltd, China), an Agilent splitter based on proprietary capillary flow technology installed between the capillary column (HP-PLOT Q; 30m x 0.32mm, Agilent Technologies Inc., USA) and detectors, and dual nitrogen phosphorus (methylamine) and flame ionization (methanol) detectors was used for this analysis. The method followed the protocol outlined in Jiang et al. (2024). The molar fraction of H&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; in headspace gas was quantified using a Reduction Gas Analyzer (Peak Performer 1, Peak Laboratories LLC, USA). All geochemical data were retrieved from the IODP database (Teske et al. 2021), while DIC concentrations in interstitial waters were reported by Torres and Kim (2022).&amp;lt;/p&amp;gt;

&amp;lt;p&amp;gt;The&amp;amp;nbsp;detection limits for the&amp;amp;nbsp;&amp;lt;/p&amp;gt;</gco:CharacterString>
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	Name: site
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http://lod.bco-dmo.org/id/dataset-parameter/991414.rdf
	Name: hole
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	Description: &lt;p&gt;Hole Designation Letter, where &quot;B&quot; represents the second hole drilled at the site location&lt;/p&gt; 
http://lod.bco-dmo.org/id/dataset-parameter/991415.rdf
	Name: latitude
	Units: decimal degrees
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http://lod.bco-dmo.org/id/dataset-parameter/991417.rdf
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http://lod.bco-dmo.org/id/dataset-parameter/991419.rdf
	Name: water_depth
	Units: m
	Description: &lt;p&gt;Water column depth&lt;/p&gt; 
http://lod.bco-dmo.org/id/dataset-parameter/991421.rdf
	Name: sediment_depth
	Units: mbsf
	Description: &lt;p&gt;Depth below the seafloor in meters&lt;/p&gt; 
http://lod.bco-dmo.org/id/dataset-parameter/991422.rdf
	Name: temperature
	Units: degrees Celsius
	Description: &lt;p&gt;Temperature&lt;/p&gt; 
http://lod.bco-dmo.org/id/dataset-parameter/991423.rdf
	Name: methane
	Units: mM
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http://lod.bco-dmo.org/id/dataset-parameter/991424.rdf
	Name: methane_flag
	Units: unitless
	Description: &lt;p&gt;Flag field where &quot;b.d.l.&quot; = below detection limit&lt;/p&gt; 
http://lod.bco-dmo.org/id/dataset-parameter/991425.rdf
	Name: methane_higher_alkane_ratio
	Units: molar ratio (C₁/C₂⁺)
	Description: &lt;p&gt;Molar ratio of methane (C₁) concentration to the summed concentrations of higher alkanes (C₂⁺; ethane and heavier hydrocarbons) in interstitial water gas&lt;/p&gt; 
http://lod.bco-dmo.org/id/dataset-parameter/991426.rdf
	Name: methane_higher_alkane_ratio_bdl_flag
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	Description: &lt;p&gt;Flag field where &quot;b.d.l.&quot; = below detection limit&lt;/p&gt; 
http://lod.bco-dmo.org/id/dataset-parameter/991427.rdf
	Name: sulfate
	Units: mM
	Description: &lt;p&gt;Sulfate concentration in interstitial water&lt;/p&gt; 
http://lod.bco-dmo.org/id/dataset-parameter/991428.rdf
	Name: dissolved_inorganic_carbon
	Units: mM
	Description: &lt;p&gt;Dissolved inorganic carbon concentration in interstitial water&lt;/p&gt; 
http://lod.bco-dmo.org/id/dataset-parameter/991429.rdf
	Name: ammonium
	Units: mM
	Description: &lt;p&gt;Ammonium concentration in interstitial water&lt;/p&gt; 
http://lod.bco-dmo.org/id/dataset-parameter/991430.rdf
	Name: methanol
	Units: µM
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http://lod.bco-dmo.org/id/dataset-parameter/991431.rdf
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	Units: nM
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                <gco:CharacterString>&amp;lt;p&amp;gt;Subsurface sediment samples were collected from four drilling sites in the Guaymas Basin, Gulf of California, during IODP Expedition 385 “Guaymas Basin Tectonics and Biosphere” using the research vessel R/V JOIDES Resolution. Rates of methanogenesis were determined at four sites. Sites 1545 (27º38.230’N, 111º53.329’W) and 1546 (27º37.884’N, 111º52.781’W) were located roughly 52 km and 51 km, respectively, northwest of the axial graben of the northern spreading segment. Both sites are highly sedimented and a 75-meter thick inactive (~thermally equilibrated) basaltic/doleritic/gabbroic sill was present at site 1546 between ~355 to 431 meters below the seafloor (mbsf). Site U1545 is considered a reference site since it was free of sill intrusions and unaffected by active hydrothermal circulation. Samples to determine methanogenesis rates were collected from the &amp;quot;B&amp;quot; hole at every site (during IODP expeditions, several, closely-spaced holes are drilled at each site so that sufficient sediment is available for all of the proposed work.)&amp;lt;/p&amp;gt;

&amp;lt;p&amp;gt;The geothermal gradient at hole U1545B was 227ºC/km. The geothermal gradient at site U1546B was similar to that measured in hole U1545B, 221ºC/km, since the sill at 1546B was thermally equilibrated. Sites U1547 (27º30.413’N, 111º40.734’W) were located inside the periphery of an active, sill-associated hydrothermal mound located about 27 km northwest of the axial graben of the northern spreading segment. Temperatures in hole U1547B exceeded 50°C in the upper 50 mbsf. The geothermal gradient at this site was between 511ºC to 960ºC/km. Site U1549 was located near a cold seep sustained by a deeply buried, thermally equilibrated sill intrusion at several hundred meters depth. The geothermal gradient at hole U1549B was 194ºC/km.&amp;lt;/p&amp;gt;

&amp;lt;p&amp;gt;Sediment samples were collected using an advanced piston coring system (APC) and a half-length APC (Teske et al. 2021). After retrieval on deck, sediment cores were sectioned in a designated core cutting area. Approximately 0.5 cm of the outer sediment layer was carefully removed to minimize potential contamination. For analysis of hydrocarbon gases, ~ 5 mL sediment was transferred into 21.5 mL clean, pre-combusted glass vials using a cut-off syringe. The vials were sealed immediately with polytetrafluoroethylene septa and aluminum caps and were incubated for 30 min at 70°C to allow dissolved hydrocarbon gases to equilibrate with the headspace before analysis, as described in Teske et al. (2021).&amp;amp;nbsp;&amp;lt;/p&amp;gt;

&amp;lt;p&amp;gt;Data describing &amp;lt;em&amp;gt;in situ &amp;lt;/em&amp;gt;geochemistry and temperature were generated shipboard, as outlined in Teske et al. (2021). Porewater for geochemical analyses was extracted from subsurface sediments using a shipboard squeezing apparatus, following established protocols (Manheim and Sayles 1974, Teske et al. 2021). To prevent contamination, ~0.5 cm of the outer sediment was carefully removed prior to transferring 150–300 cm&amp;lt;sup&amp;gt;3&amp;lt;/sup&amp;gt; of uncontaminated interior material into a titanium squeezing vessel. The vessel was placed in a Carver hydraulic press (Manheim and Sayles 1974), and the expressed porewater was filtered immediately through a 0.2 µm polyethersulfone membrane. Filtrates were collected in HCl-washed syringes and subsampled into acid-cleaned high-density polyethylene vials for onboard determinations of sulfate and ammonium, with samples stored at 4 °C following fixation (acidification with trace metal grade nitric acid for sulfate and phenol solution for ammonium).&amp;lt;/p&amp;gt;

&amp;lt;p&amp;gt;Dissolved inorganic carbon (DIC) was collected into 2 mL glass vials and preserved with 10 µL of saturated HgCl&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; for shore-based analysis. For acetate analysis, 2 mL porewater subsamples were preserved immediately after collection and stored frozen at −20 °C in pre-combusted glass vials with Teflon-coated screw caps (Heuer et al. 2009). Samples for methanol and trimethylamine (TMA) measurements were transferred immediately into pre-combusted and N&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;-purged 20 mL glass vials that were sealed with gas-tight butyl rubber stoppers, stored at −80°C until analysis.&amp;lt;/p&amp;gt;

&amp;lt;p&amp;gt;Hydrocarbon gas analysis was performed by extracting about 5 mL of headspace gas from the 21.5 mL vials using a gas-tight syringe and directly injecting it into an Agilent 7890A gas chromatograph with a flame ionization detector (FID) (Teske et al. 2021). Sulfate concentrations were measured by ion chromatography using a Metrohm 850 Professional IC system (Murray et al. 2000, Teske et al. 2021). Ammonium concentrations were determined by a colorimetric method involving phenol diazotization followed by oxidation with bleach (Clorox) to produce a blue color, measured at 640 nm using a Cary Series 100 UV-Vis spectrophotometer (Agilent Technologies) (Solorzano 1969, Teske et al. 2021). Samples were diluted beforehand to keep ammonium below 1000 μM. Methanol and TMA (~5 mL) in porewater were simultaneously quantified using a purge and trap pre-treatment system coupled with a gas chromatograph (Jiang et al. 2024). An Agilent Technologies Inc. (USA) 8890 gas chromatograph equipped with a purge and trap system (Acrichi PTC, Beijing Juxin Zhuifeng Technology, Ltd, China), an Agilent splitter based on proprietary capillary flow technology installed between the capillary column (HP-PLOT Q; 30m x 0.32mm, Agilent Technologies Inc., USA) and detectors, and dual nitrogen phosphorus (methylamine) and flame ionization (methanol) detectors was used for this analysis. The method followed the protocol outlined in Jiang et al. (2024). The molar fraction of H&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; in headspace gas was quantified using a Reduction Gas Analyzer (Peak Performer 1, Peak Laboratories LLC, USA). All geochemical data were retrieved from the IODP database (Teske et al. 2021), while DIC concentrations in interstitial waters were reported by Torres and Kim (2022).&amp;lt;/p&amp;gt;

&amp;lt;p&amp;gt;The&amp;amp;nbsp;detection limits for the&amp;amp;nbsp;&amp;lt;/p&amp;gt;</gco:CharacterString>
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                  <gco:CharacterString>- Imported &amp;quot;OCE-2023575_Methanogenesis_geochemistry_csv.csv&amp;quot; into BCO-DMO system
- Created new field &amp;quot;methane_flag&amp;quot; and moved all &amp;quot;b.d.l.&amp;quot; values to this new flag field and removed them from the &amp;quot;methane&amp;quot; field
- Created new field &amp;quot;methane_higher_alkane_ratio_bdl_flag&amp;quot; and moved all &amp;quot;b.d.l.&amp;quot; values to this new flag field and removed them from the &amp;quot;methane/ higher alkanes&amp;quot; field
- Renamed fields to comply with BCO-DMO naming conventions, removing units, special characters, and spaces
- Exported file as &amp;quot;991374_v1_methanogenesis_geochem_guaymas_basin.csv&amp;quot;</gco:CharacterString>
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More information is available from IODP (PDF).</gco:CharacterString>
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Hydrogen: Peak Laboratories LLC (USA) Peak Performer 1 Reduction Gas Analyzer. The instrument was calibrated with certified gas standards containing  10 ppm hydrogen. Nitrogen served as a carrier gas. Dilution of the primary standard into ultra high purity (UHP, 99.999%) nitrogen using a calibrated gas-tight syringe was used to generate working standards (0, 1, 2.5, 5 and 10 ppm hydrogen). Both the certified hydrogen standard and the UHP nitrogen was obtained from AirGas. Blanks and at least one check standard was run routinely, every 8 to 10 samples. Instrument Name: Gas Analyzer Instrument Short Name:Gas Analyzer   Instrument Description: Gas Analyzers - Instruments for determining the qualitative and quantitative composition of gas mixtures.</gco:CharacterString>
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            <gco:CharacterString>PI Supplied Instrument Name: Agilent 7890A gas chromatograph with a flame ionization detector (FID) PI Supplied Instrument Description:Hydrocarbon gas analysis was performed by extracting about 5 mL of headspace gas from the 21.5 mL vials using a gas-tight syringe and directly injecting it into an Agilent 7890A gas chromatograph with a flame ionization detector (FID) (Teske et al. 2021b).  Instrument Name: Gas Chromatograph Instrument Short Name:Gas Chromatograph   Instrument Description: Instrument separating gases, volatile substances, or substances dissolved in a volatile solvent by transporting an inert gas through a column packed with a sorbent to a detector for assay. (from SeaDataNet, BODC) Community Standard Description: http://vocab.nerc.ac.uk/collection/L05/current/LAB02/</gco:CharacterString>
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      <gmi:instrument>
        <gmi:MI_Instrument>
          <gmi:identifier>
            <gmd:MD_Identifier>
              <gmd:code>
                <gmx:Anchor xlink:href="http://lod.bco-dmo.org/id/instrument/661.rdf" xlink:title="Gas Chromatograph" xlink:actuate="onRequest">Agilent Technologies Inc. (USA) 8890 gas chromatograph</gmx:Anchor>
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            <gco:CharacterString>Agilent Technologies Inc. (USA) 8890 gas chromatograph</gco:CharacterString>
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            <gco:CharacterString>PI Supplied Instrument Name: Agilent Technologies Inc. (USA) 8890 gas chromatograph PI Supplied Instrument Description:An Agilent Technologies Inc. (USA) 8890 gas chromatograph equipped with a purge and trap system (Acrichi PTC, Beiging Juxin Zhuifeng Technology, Ltd, China), an Agilent splitter based on proprietary capillary flow technology installed between the capillary column (HP-PLOT Q; 30m x 0.32mm, Agilent Technologies Inc., USA) and detectors, and dual nitrogen phosphorus (methylamine) and flame ionization (methanol) detectors was used for this analysis. 
Methanol and Methylamine: Agilent 8890 gas chromatograph. Trimethylamine hydrochloride (98%) and methanol (analytical grade reagents) were purchased from Merck (KGaA, Germany) and Sinopharm Chemical Reagent, Ltd (Shanghai, China), respectively. The primary stocks of trimethylamine (1.2 mM) and methanol (12.3 mM) were prepared separately in double-distilled water and both stock solutions were stored &lt; 1 week in a 50 mL serum vial without headspace at 4°C in the dark. Standard solutions for calibration (trimethylamine: 0.5 – 7.2 nM; methanol: 24.0 – 360.0 nM) were made by mixing and diluting the trimethylamine and methanol primary stocks to desired concentrations. Ammonium chloride (&gt; 99.5%) and sodium hydroxide (&gt; 96%) were purchased from Sinopharm Chemical Reagent Co., Ltd (Shanghai, China). Instrument Name: Gas Chromatograph Instrument Short Name:Gas Chromatograph   Instrument Description: Instrument separating gases, volatile substances, or substances dissolved in a volatile solvent by transporting an inert gas through a column packed with a sorbent to a detector for assay. (from SeaDataNet, BODC) Community Standard Description: http://vocab.nerc.ac.uk/collection/L05/current/LAB02/</gco:CharacterString>
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      </gmi:instrument>
      <gmi:instrument>
        <gmi:MI_Instrument>
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              <gmd:code>
                <gmx:Anchor xlink:href="http://lod.bco-dmo.org/id/instrument/662.rdf" xlink:title="Ion Chromatograph" xlink:actuate="onRequest">Metrohm 850 Professional IC system</gmx:Anchor>
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            <gco:CharacterString>Metrohm 850 Professional IC system</gco:CharacterString>
          </gmi:type>
          <gmi:description>
            <gco:CharacterString>PI Supplied Instrument Name: Metrohm 850 Professional IC system PI Supplied Instrument Description:Sulfate and chloride concentrations were measured by ion chromatography using a Metrohm 850 Professional IC system (Murray et al. 2000, Teske et al. 2021).  Instrument Name: Ion Chromatograph Instrument Short Name:Ion Chromatograph   Instrument Description: Ion chromatography is a form of liquid chromatography that measures concentrations of ionic species by separating them based on their interaction with a resin. Ionic species separate differently depending on species type and size. Ion chromatographs are able to measure concentrations of major anions, such as fluoride, chloride, nitrate, nitrite, and sulfate, as well as major cations such as lithium, sodium, ammonium, potassium, calcium, and magnesium in the parts-per-billion (ppb) range. (from http://serc.carleton.edu/microbelife/research_methods/biogeochemical/ic.html)</gco:CharacterString>
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      <gmi:instrument>
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              <gmd:code>
                <gmx:Anchor xlink:href="http://lod.bco-dmo.org/id/instrument/707.rdf" xlink:title="Spectrophotometer" xlink:actuate="onRequest">Cary Series 100 UV-Vis spectrophotometer (Agilent Technologies)</gmx:Anchor>
              </gmd:code>
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            <gco:CharacterString>Cary Series 100 UV-Vis spectrophotometer (Agilent Technologies)</gco:CharacterString>
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          <gmi:description>
            <gco:CharacterString>PI Supplied Instrument Name: Cary Series 100 UV-Vis spectrophotometer (Agilent Technologies) PI Supplied Instrument Description:Ammonium concentrations were determined by a colorimetric method involving phenol diazotization followed by oxidation with bleach (Clorox) to produce a blue color, measured at 640 nm using a Cary Series 100 UV-Vis spectrophotometer (Agilent Technologies) (Solorzano 1969, Teske et al. 2021).  Instrument Name: Spectrophotometer Instrument Short Name:Spectrophotometer   Instrument Description: An instrument used to measure the relative absorption of electromagnetic radiation of different wavelengths in the near infra-red, visible and ultraviolet wavebands by samples. Community Standard Description: http://vocab.nerc.ac.uk/collection/L05/current/LAB20/</gco:CharacterString>
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      </gmi:instrument>
      <gmi:instrument>
        <gmi:MI_Instrument>
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              <gmd:code>
                <gmx:Anchor xlink:href="http://lod.bco-dmo.org/id/instrument/682.rdf" xlink:title="Titrator" xlink:actuate="onRequest">Metrohm 794 Basic Titrino autotitrator</gmx:Anchor>
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            <gco:CharacterString>Metrohm 794 Basic Titrino autotitrator</gco:CharacterString>
          </gmi:type>
          <gmi:description>
            <gco:CharacterString>PI Supplied Instrument Name: Metrohm 794 Basic Titrino autotitrator PI Supplied Instrument Description:Total alkalinity was measured by Gran titration with a Metrohm 794 Basic Titrino autotitrator (Gieskes et al. 1991, Teske et al. 2021).  Instrument Name: Titrator Instrument Short Name:Titrator   Instrument Description: Titrators are instruments that incrementally add quantified aliquots of a reagent to a sample until the end-point of a chemical reaction is reached. Community Standard Description: http://vocab.nerc.ac.uk/collection/L05/current/LAB12/</gco:CharacterString>
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            <gmi:parentOperation gco:nilReason="inapplicable"/>
            <gmi:platform>
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         <gmx:Anchor xlink:href="http://www-odp.tamu.edu/resolutn.html" xlink:actuate="onRequest">R/V JOIDES Resolution</gmx:Anchor>
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    </gmi:citation>
    <gmi:citation>
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              <gmx:Anchor xlink:href="http://lod.bco-dmo.org/id/authority/1.rdf" xlink:actuate="onRequest">International Council for the Exploration of the Sea</gmx:Anchor>
            </gmd:title>
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        </gmd:authority>
        <gmd:code>
          <gmx:Anchor xlink:href="http://lod.bco-dmo.org/id/platform/521575.rdf"
           xlink:title="54JR" xlink:actuate="onRequest">R/V JOIDES Resolution</gmx:Anchor>
        </gmd:code>
      </gmd:MD_Identifier>
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    <gmi:description>
      <gmx:Anchor xlink:href="http://lod.bco-dmo.org/id/platform/521575.rdf" xlink:title="R/V JOIDES Resolution" xlink:actuate="onRequest">vessel</gmx:Anchor>
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                      <gmd:CI_ResponsibleParty>
                      <gmd:individualName>
                          <gmx:Anchor xlink:href="http://lod.bco-dmo.org/id/person/51412.rdf" xlink:actuate="onRequest">Andreas Teske</gmx:Anchor>
                        </gmd:individualName>
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                        <gmd:CI_RoleCode codeList="http://www.isotc211.org/2005/resources/Codelist/gmxCodelists.xml#CI_RoleCode" codeListValue="principalInvestigator"/>
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         <gmx:Anchor xlink:href="http://www-odp.tamu.edu/resolutn.html" xlink:actuate="onRequest">R/V JOIDES Resolution</gmx:Anchor>
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         <gmx:Anchor xlink:href="http://vocab.nerc.ac.uk/collection/C17/current/54JR/" xlink:actuate="onRequest">Community Standard Description</gmx:Anchor>
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          <gmx:Anchor xlink:href="http://lod.bco-dmo.org/id/platform/521575.rdf"
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      </gmd:MD_Identifier>
    </gmi:identifier>
    <gmi:description>
      <gmx:Anchor xlink:href="http://lod.bco-dmo.org/id/platform/521575.rdf" xlink:title="R/V JOIDES Resolution" xlink:actuate="onRequest">vessel</gmx:Anchor>
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