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Holmes, M Elizabeth; Lavik, Gaute; Fischer, Gerhard; Segl, Monika; Ruhland, Götz; Wefer, Gerold (2002): d15N of trap WR2. PANGAEA,, Supplement to: Holmes, ME et al. (2002): Seasonal variability of d15N in sinking particles in the Benguela upwelling region. Deep Sea Research Part I: Oceanographic Research Papers, 49(2), 377-394,

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Temporal changes in d15N values of sinking particles collected with sediment traps in the Benguela upwelling regime off southwest Africa mirrored variations in the input of inorganic nitrogen to the surface water. Reductions in d15N (to as low as 2.5 per mil) corresponded to low sea surface temperatures during austral spring and late austral autumn/early winter, indicating increased nitrate availability due to the presence of recently upwelled water. High particulate fluxes accompanied the low d15N values and sea surface temperatures, reflecting increased productivity, fueled by the upwelled nutrients. High d15N values (up to 13.1 per mil) coincided with high sea surface temperatures and low particle fluxes. In this area, the seaward extension of upwelling filaments, which usually occurs twice yearly, brings nutrient-rich water to the euphotic zone and leads to elevated productivity and relatively lower d15N values of the particulate nitrogen. Satellite images of ocean chlorophyll show that productivity variations coincide with d15N changes. The observed isotopic pattern does not appear to have been caused by variations in the species composition of the phytoplankton assemblage. Calculations based on d15N of the sinking particulate nitrogen show that the surface nitrate pool was more depleted during late austral summer/early fall and mid-winter and that supply exceeded demand during the intense spring bloom and in late austral fall. The main uncertainty associated with these estimates is the effect of diagenesis on d15N and possible variability in preservation of the isotope signal between periods of high and low particle flux.
Related to:
Holmes, M Elizabeth (1996): Reconstruction of surface ocean nitrate utilization in the Southeast Atlantic Ocean based on stable nitrogen isotopes. Berichte aus dem Fachbereich Geowissenschaften der Universität Bremen, 83, 113 pp, urn:nbn:de:gbv:46-ep000102121
Latitude: -20.050000 * Longitude: 9.150000
Date/Time Start: 1989-03-18T00:00:00 * Date/Time End: 1990-02-23T00:00:00
Minimum DEPTH, water: 599 m * Maximum DEPTH, water: 599 m
WR2_trap * Latitude: -20.050000 * Longitude: 9.150000 * Date/Time Start: 1989-03-18T00:00:00 * Date/Time End: 1990-03-13T00:00:00 * Elevation: -2196.0 m * Location: Walvis Ridge, Southeast Atlantic Ocean * Campaign: ANT-VII/5 (PS14) * Basis: Polarstern * Method/Device: Trap (TRAP)
#NameShort NameUnitPrincipal InvestigatorMethod/DeviceComment
1DEPTH, waterDepth watermGeocode
3Date/time endDate/time endHolmes, M Elizabeth
4Duration, number of daysDurationdaysHolmes, M Elizabeth
5Sample code/labelSample labelHolmes, M Elizabeth
6δ15N, gasδ15N-N2‰ airHolmes, M ElizabethMass spectrometer Finnigan MAT 251
80 data points

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