Location:\u00a0North Atlantic, western flank of the mid-Atlantic Ridge\u00a022.75589 N 46.08125 W
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Methodology:
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Prior to the extraction, we freeze-dried, ground and sieved sediment samples to less than 125 \u03bcm (Ruttenberg 1992). For a given sample, we weighed four sample replicates (2 g) and placed each in 250 mL HDPE bottles. Sodium dithionite (F.W. 147.12 g/mol; 7.4 g) was added to each sample split, followed by 200 mL of citrate-bicarbonate solution (pH 7.6). This step produces effervescence, so the solution should be added slowly to the sample. We shook samples for 8 h and then centrifuged them at 3,700 rpm for 15 min. We filtered the supernatants with a 0.4 \u03bcm polycarbonate filter. We took 20 mL aliquots from the filtrate for each sample split for MRP and total P analyses, and kept them refrigerated until analysis within 24 h. We added 200 mL of ultrapure water to the solid residue for each sample split as a wash step after the above reductive step, shook samples for 2 h, and then centrifuged them at 3,700 rpm for 15 min. We filtered the supernatants with 0.4 \u03bcm polycarbonate filters and set aside 20 mL of filtrate from each sample split for MRP and total P analyses. We then extracted the solid sample residues in 200 mL of sodium acetate buffer (pH 4.0) for 6 h. At the end of this extraction step, we centrifuged the bottles at 3,700 rpm for 15 min, filtered the supernatants with 0.4 \u03bcm polycarbonate filters and took a 20 mL aliquot of filtrate from each sample split for MRP and total P analyses. We added 200 mL of ultrapure water to the solid residue for each sample split as a wash step, shook samples for 2 h, and then centrifuged them at 3,700 rpm for 15 min.\u00a0 We filtered the supernatants with 0.4 \u03bcm polycarbonate filters and set aside 20 mL of filtrate from each sample split for MRP and total P analyses. We repeated the water rinse step, and collected aliquots for MRP and total P analyses as in the previous steps. The concentrations of\u00a0 MRP were determined as described below.
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The MRP concentrations were measured on a QuikChem 8000 automated ion analyzer. Standards were prepared with the same solutions used for the extraction step to minimize matrix effects on P measurements. Sediment extracts and standards (0 \u2013 30 \u03bcM PO4) were diluted ten-fold to prevent matrix interference with color development. The detection limit for P on this instrument is 0.2 \u03bcM. We derived MUP concentrations by subtracting MRP from total P concentrations, which are included in a different spreadsheet.
Molybdate reactive phosphorus concentrations in nuclear magnetic resonance (NMR) pretreatment extracts from sediment samples collected during R/V JOIDES Resolution cruise JRES-336 (IODP336, North Pond) to the western flank of the mid-Atlantic Ridge in November of 2011.\u00a0\u00a0Samples were analyzed in 2016.
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These data were published in Defforey et al. (2016). See the related-resource page https://www.bco-dmo.org/project/664073 for other datasets related to this publication.
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\u200bAdditional award information:
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* NSF C-DEBI subaward # 156246 to Adina Paytan
\n* NSF C-DEBI subaward # 157598 to Delphine Defforey
Data were processed in Excel.
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BCO-DMO Data Manager Processing Notes:
\n* Data from originally submitted Excel file Data_MRP.xlsx exported as csv.\u00a0 Sheets for step 1 and step 2 combined into one data table.\u00a0 Values exported as formatted in excel with decimals with three decimal places.
\n* added a conventional header with dataset name, PI name, version date
\n* modified parameter names to conform with BCO-DMO naming conventions
\n* blank values in this dataset are displayed as \"nd\" for \"no data.\" nd is the default missing data identifier in the BCO-DMO system.
\n* Date format changed to ISO 8601 format yyyy-mm-dd