<div><p>The methods on how the samples were collected and processed for the attached dataset can be found in the methodology section of Flynn et al. (2019). </p>
<p>Hydrographic measurements were made using a conductivity-temperature-depth (CTD) profiler fitted with a temperature, salinity and oxygen sensor. </p>
<p>Nitrate+nitrite concentrations were measured following published auto-analysis protocols (Diamond 1994; Grasshoff 1976), and nitrite and phosphate concentrations were determined using benchtop colourimetric methods (Strickland and Parsons 1968; Bendschneider and Robinson 1952; Parsons et al. 1984). </p>
<p>Nitrate N and O isotope ratios were measured using the “denitrifier method” (Sigman et al. 2001; Casciotti et al. 2002; McIlvin and Casciotti 2011).</p>
<p>Seawater samples were collected at discrete depths from the surface to the seafloor using a tethered rosette holding twelve 6-L Niskin bottles. At each CTD station, nutrient and nitrate isotope samples were collected filtered (0.22 µm PES membrane syringe filter) throughout the water column in 60 mL HDPE bottles. Each bottle was rinsed three times prior to being filled, and then immediately frozen at -20°C pending analysis. All nutrient samples were analysed within a year from collection, and nitrate isotopes within 18 months of collection. </p></div>
Nutrient and nitrate isotope data from the southern Benguela upwelling system from February to August 2017
<div><p>CTD data:<br />
The temperature and conductivity probes are calibrated annually by the manufacturer while the oxygen sensor was calibrated against discrete seawater samples analyzed for dissolved oxygen concentrations by Winkler titration (Carpenter 1965; Grasshoff et al. 1983).</p>
<p>Nutrients:<br />
Duplicate samples were measured for nitrate+nitrite on different days, and the standard deviation for duplicates was <0.5 µM, with a lower standard deviation for lower concentration samples<br />
Duplicate samples for phosphate and nitrite were measured in duplicate on different days of analysis, yielding a standard deviation for duplicates of ≤0.1 µM. </p>
<p>Nitrate isotopes:<br />
The N and O isotope ratios of nitrate were measured in triplicate in separate batch analyses and standard deviations for both δ15N and δ18O were <0.3‰. Certified nitrate isotope ratio reference materials in nutrient-free seawater were measured in all batch analyses. These included IAEA-NO3-, with δ15N of 4.7 ± 0.2‰ vs. N2 air (Gonfiantini et al. 1995) and and δ18O of 25.6 ± 0.4‰ vs. VSMOW (Böhlke et al. 2003), and USGS-34, with δ15N of -1.8 ± 0.1‰ vs. N2 air and δ18O of -27.9 ± 0.3‰ vs. VSMOW (Böhlke et al. 2003). Nitrate isotstandards in individual runs were diluted in nutrient-free seawater to concentrations similar to those of the samples to account for potential matrix effects on the δ18O measurements (Weigand et al. 2016). Reproducibility was monitored by analysis of an internal seawater nitrate standard from the deep North Atlantic.</p></div>
IEP February and May 2017
<div><p>BCO-DMO Processing Notes:<br />
- added conventional header with dataset name, PI name, version date<br />
- modified parameter names to conform with BCO-DMO naming conventions<br />
- converted positive latitude values for SHGML005 in May 2017 to negative values as they were incorrect.<br />
- removed extra data row at bottom of Aug sheet.</p></div>
811839
IEP February and May 2017
2020-05-19T14:41:00-04:00
2020-05-19T14:41:00-04:00
2023-07-07T16:10:26-04:00
urn:bcodmo:dataset:811839
Nutrient and nitrate isotope data from the southern Benguela upwelling system from February to August 2017
Analysed Particulate Organic Matter data, Nutrient data and Nitrate isotope data from the 2017 Integrated Ecosystem Programme: Southern Benguela (IEP:SB) cruises conducted in February, May, and August 2017. The IEP:SB is a multi-disciplinary, multi-institutional platform to undertake relevant science in the Southern Benguela; also functioning as a platform for collaboration and learning.
Nitrate+nitrite concentrations were measured on a Lachat QuickChem flow injection analysis platform in a configuration with a detection limit of 0.1 µM, while phosphate and nitrite concentrations were measured using standard benchtop techniques on a Thermo Scientific Genesis 30 Visible spectrophotometer in a configuration with a detection limit of 0.05 µM. The N and O isotope ratios of the N2O gas were analysed using a Delta V Advantage continuous flow isotope ratio mass spectrometer interfaced with an online N2O extraction and purification system.
false
Granger, J., Siedlecki, S. (2020) Nutrient and nitrate isotope data from the southern Benguela upwelling system from February to August 2017. Biological and Chemical Oceanography Data Management Office (BCO-DMO). (Version 1) Version Date 2020-05-19 [if applicable, indicate subset used]. doi:10.26008/1912/bco-dmo.811839.1 [access date]
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10.26008/1912/bco-dmo.811839.1
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2020-05-19
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