Nagel, Birgit; Emeis, Kay-Christian; Flohr, Anita; Rixen, Tim; Schlarbaum, Tim; Mohrholz, Volker; van der Plas, Anja K (2018): Nutrients and δ15N measured in water samples in the oxygen minimum zone over the Namibian shelf during the Meteor campaign M76-2 in 2008 [dataset]. PANGAEA, https://doi.org/10.1594/PANGAEA.892369, Supplement to: Nagel, B et al. (2013): N-cycling and balancing of the N-deficit generated in the oxygen minimum zone over the Namibian shelf-An isotope-based approach. Journal of Geophysical Research: Biogeosciences, 118(1), 361-371, https://doi.org/10.1002/jgrg.20040
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Abstract:
The northern Benguela upwelling system is a nutrient‐replete region with high plankton biomass production and a seasonally changing oxygen minimum zone. Nitrate:phosphate ratios in fresh upwelling water are low due to denitrification in the near‐seafloor oxygen minimum zone and phosphate efflux from sediments. This makes the region a candidate for substantial dinitrogen fixation, for which evidence is scarce. Nutrient and oxygen data, N isotope data of nitrate, nitrogen isotope ratios of particulate matter, particulate organic carbon content, and suspended matter concentrations on a transect across the shelf and upper slope at 23°S illustrate N‐cycling processes and are the basis for estimating the contribution of N‐sources and N‐sinks to the reactive nitrogen pool. It appears that N‐removal due to denitrification exceeds N gain by N2 fixation and physical mixing processes by a factor of >6, although inorganic N:P ratios again increase as surface water is advected offshore. Nitrate and ammonium regeneration, nutrient assimilation with N:P < 16, shelf break mixing, atmospheric input, and N2 fixation all contribute to the restoration of inorganic N:P ratios back to Redfield conditions, but in seasonally changing proportions. The Benguela upwelling system thus is a nutrient source for the oceanic‐mixed layer where N‐sources and N‐sinks are not in balance and Redfield conditions can only re‐adjust by advection and mixing processes integrated over time.
Related to:
Emeis, Kay-Christian (2015): Nutrients measurements from METEOR cruise M76/2 in the Benguela Upwelling System off Namibia in May 2008. Institute for Geology, Biogeochemistry, University of Hamburg, PANGAEA, https://doi.org/10.1594/PANGAEA.854075
Project(s):
Funding:
Bundesministerium für Bildung und Forschung, Bonn (BMBF), grant/award no. 03F0650: Geochemistry and ecology of the Namibian upwelling system
Coverage:
Median Latitude: -21.420389 * Median Longitude: 13.037872 * South-bound Latitude: -23.003000 * West-bound Longitude: 10.649830 * North-bound Latitude: -17.415500 * East-bound Longitude: 14.367670
Date/Time Start: 2008-05-17T00:00:00 * Date/Time End: 2008-05-31T00:00:00
Minimum DEPTH, water: 1.00 m * Maximum DEPTH, water: 3000.00 m
Event(s):
M76/2_192_WS * Latitude: -23.000330 * Longitude: 14.367670 * Date/Time: 2008-05-17T00:00:00 * Elevation: -37.0 m * Location: Namibia upwelling, Southeast Atlantic * Campaign: M76/2 * Basis: Meteor (1986) * Method/Device: Water sample (WS)
M76/2_194_WS * Latitude: -22.999170 * Longitude: 14.215830 * Date/Time: 2008-05-17T00:00:00 * Elevation: -101.0 m * Location: Namibia upwelling, Southeast Atlantic * Campaign: M76/2 * Basis: Meteor (1986) * Method/Device: Water sample (WS)
M76/2_195_WS * Latitude: -23.000000 * Longitude: 14.048830 * Date/Time: 2008-05-17T00:00:00 * Elevation: -128.0 m * Location: Namibia upwelling, Southeast Atlantic * Campaign: M76/2 * Basis: Meteor (1986) * Method/Device: Water sample (WS)
Parameter(s):
| # | Name | Short Name | Unit | Principal Investigator | Method/Device | Comment |
|---|---|---|---|---|---|---|
| 1 | Event label | Event | Emeis, Kay-Christian | |||
| 2 | Latitude of event | Latitude | Emeis, Kay-Christian | |||
| 3 | Longitude of event | Longitude | Emeis, Kay-Christian | |||
| 4 | Date/Time of event | Date/Time | Emeis, Kay-Christian | |||
| 5 | Elevation of event | Elevation | m | Emeis, Kay-Christian | ||
| 6 | DEPTH, water | Depth water | m | Emeis, Kay-Christian | Geocode | |
| 7 | Temperature, water | Temp | °C | Emeis, Kay-Christian | CTD | |
| 8 | Salinity | Sal | Emeis, Kay-Christian | CTD | Measured in water column | |
| 9 | Oxygen | O2 | µmol/l | Emeis, Kay-Christian | Clarke-type sensor | Measured in water column |
| 10 | Fluorescence | Fluorescence | arbitrary units | Emeis, Kay-Christian | CTD | measured in water column |
| 11 | Nitrate | [NO3]- | µmol/l | Emeis, Kay-Christian | Colorimetric | Measured in water column. Standard-calorimetric method (according to Grasshoff et al. 1999), with auto-analyser. Average of the measurement of 2 replicates. |
| 12 | Phosphate | [PO4]3- | µmol/l | Emeis, Kay-Christian | Colorimetric | Measured in water column. Standard-calorimetric method (according to Grasshoff et al. 1999), with auto-analyser. Average of the measurement of 2 replicates. |
| 13 | Silicate | Si(OH)4 | µmol/l | Emeis, Kay-Christian | Colorimetric | Measured in water column. Standard-calorimetric method (according to Grasshoff et al. 1999), with auto-analyser. Average of the measurement of 2 replicates. |
| 14 | Ammonium | [NH4]+ | µmol/l | Emeis, Kay-Christian | Colorimetric | Measured in water column. Standard-calorimetric method (according to Grasshoff et al. 1999), with auto-analyser. Average of the measurement of 2 replicates. |
| 15 | Nitrite | [NO2]- | µmol/l | Emeis, Kay-Christian | Colorimetric | Measured in water column. Standard-calorimetric method (according to Grasshoff et al. 1999), with auto-analyser. Average of the measurement of 2 replicates. |
| 16 | δ15N, nitrate | δ15N NO3 | ‰ air | Emeis, Kay-Christian | Isotope ratio mass spectrometry | Measured in water column. Measurement as N2O using isotope-ratio mass spectrometry (IRMS). Bacterial conversion to N2O, so called Denitrifier-method (according to Sigman et al. 2001; Casciotti et al. 2002). Average of the measurement of 2 replicates. |
License:
Creative Commons Attribution 3.0 Unported (CC-BY-3.0)
Size:
1468 data points