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| Titel |
Seasonal, daily and diel N2 effluxes in permeable carbonate sediments |
| VerfasserIn |
B. D. Eyre, I. R. Santos, D. T. Maher |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 10, no. 4 ; Nr. 10, no. 4 (2013-04-18), S.2601-2615 |
| Datensatznummer |
250018206
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| Publikation (Nr.) |
 copernicus.org/bg-10-2601-2013.pdf |
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| Zusammenfassung |
| Benthic metabolism and inorganic nitrogen and N2 flux rates
(denitrification) were measured in permeable carbonate sands from Heron
Island (Great Barrier Reef). Some of the N2 flux rates were among the
highest measured in sediments. All benthic fluxes showed a significant
difference between seasons with higher rates in summer and late summer. There
was no distinct response of the benthic system to mass coral spawning.
Instead, changes in benthic fluxes over 12 days in summer appear to be driven
by tidal changes in water depth and associated changes in phytosynthetically
active radiation reaching the sediments. Dark N2 fluxes were strongly
correlated to benthic oxygen consumption across all sites and seasons (r2
= 0.63; p < 0.005; slope = 0.035). However, there were seasonal
differences with a steeper slope in summer than winter, reflecting either
more efficient coupling between respiration and
nitrification–denitrification at higher temperatures or different sources of
organic matter. Adding data from published studies on carbonate sands
revealed two slopes in the dark N2 flux versus benthic oxygen
consumption relationship. The lower slope (0.035) was most likely due to high
carbon : nitrogen (C : N) organic matter from coral reefs, and associated
assimilation of nitrogen by heterotrophic bacteria including enhanced
heterotrophic N-fixation, but competition by benthic microalgae or
inefficient coupling between respiration and nitrification–denitrification
cannot be excluded. The steeper slope (0.089) was most likely due to
respiration being driven by low C : N phytodetritus. If the different
slopes were driven by the sources of organic matter, then global estimates of
continental shelf denitrification are probably about right. In contrast,
global estimates of continental shelf denitrification may be over-estimated
if the low slope was due to inefficient coupling between respiration and
nitrification–denitrification and also due to reduced N2 effluxes in
the light associated with competition by benthic microalgae for nitrogen and
N-fixation. |
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