Locations:
\n
Arctic Ocean: P-1-94-AR P21, 84\u00b05' N, 174\u00b058' W
\nCalifornia margin: W-2-98-NC TF1, 41\u00b05' N, 125\u00b01' W
\nEquatorial Pacific: TT013-06MC, 12\u00b000' S, 134\u00b056' W
\n
Methodology:
\n
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. 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 MRP were determined as described below.
\n
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 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 dataset.
Molybdate reactive phosphorus concentrations in nuclear magnetic resonance (NMR) pretreatment extracts from sediment samples collected during cruises in the Arctic Ocean, California Margin, and Equatorial Pacific from 1992-1998.
\n
These data were published in Defforey et al. (2017). See the related-resource page https://www.bco-dmo.org/related-resource/794727 for other datasets related to this publication.
\n
Sediment sample information for this dataset is available as a supplemental document (Sediment_Sample_Info.csv) which contains collection date, water depth, sediment depth, latitude, and longitude.
\n
\u200bAdditional award information:
\n
* NSF C-DEBI subaward # 156246 to Adina Paytan
\n* NSF C-DEBI subaward # 157598 to Delphine Defforey
Data were processed in Excel.
\n
BCO-DMO Data Manager Processing Notes:
\n* Data from originally submitted Excel file Data_MRP_sediments with pretreatment_v2.xlsx in sheet "Step 1" and "Step 2" were combined and exported as csv.
\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* PO4 values with eight decimal places in the Sheet "Step 2" were rounded to two decimal places to match the precision of other values in the column.
\n* Concentration_Units column with all values uM removed. This information is captured in the Parameter descriptions.