Publikationsdatum:
2012-08-08
Beschreibung:
Excess nitrogen gas (excess N2) was measured in samples collected at six locations in the eastern and western sub-basins of the Cariaco Basin, Venezuela, in September 2008 (non-upwelling conditions) and March 2009 (upwelling conditions). During both sampling periods, excess N2 concentrations were below detection in surface waters, increasing to ~22 μmol N kg−1 at the oxic-anoxic interface ([O2] 〈 ~ 4 μmol N kg−1, ~250 m). Below the oxic-anoxic interface (300–400 m), the average concentration of excess N2 was 24.7 ± 1.9 μmol N kg−1 in September 2008 and 27.5 ± 2.0 μmol N kg−1 in March 2009, i.e., excess N2 concentrations within this depth interval were ~ 3 μmol N kg−1 higher (p 〈 0.001) during the upwelling season compared to the non-upwelling period. These results suggest that N-loss in the Cariaco Basin may vary seasonally in response to changes in the flux of sinking particulate organic matter. We attribute the increase in excess N2 concentrations, or N-loss, observed during upwelling to: (1) higher availability of fixed nitrogen derived from suspended and sinking particles at the oxic-anoxic interface and/or (2) enhanced ventilation at the oxic-anoxic interface during upwelling.
Print ISSN:
1810-6277
Digitale ISSN:
1810-6285
Thema:
Biologie
,
Geologie und Paläontologie
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