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| Titel |
Effects of fluctuating hypoxia on benthic oxygen consumption in the Black Sea (Crimean shelf) |
| VerfasserIn |
A. Lichtschlag, D. Donis, F. Janssen, G. L. Jessen, M. Holtappels, F. Wenzhöfer, S. Mazlumyan, N. Sergeeva, C. Waldmann, A. Boetius  |
| 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 ; 12, no. 16 ; Nr. 12, no. 16 (2015-08-27), S.5075-5092 |
| Datensatznummer |
250118076
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| Publikation (Nr.) |
 copernicus.org/bg-12-5075-2015.pdf |
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| Zusammenfassung |
| The outer western Crimean shelf of the Black Sea is a natural laboratory to
investigate effects of stable oxic versus varying hypoxic conditions on
seafloor biogeochemical processes and benthic community structure.
Bottom-water oxygen concentrations ranged from normoxic (175 μmol
O2 L−1) and hypoxic (< 63 μmol O2 L−1) or
even anoxic/sulfidic conditions within a few
kilometers' distance. Variations in oxygen concentrations between 160 and 10 μmol L−1 even occurred
within hours close to the chemocline at 134 m water depth. Total oxygen
uptake, including diffusive as well as fauna-mediated oxygen consumption, decreased from 15 mmol m−2 d−1 on average in the
oxic zone, to 7 mmol m−2 d−1 on average in the hypoxic zone,
correlating with changes in macrobenthos composition. Benthic diffusive
oxygen uptake rates, comprising respiration of microorganisms and small
meiofauna, were similar in oxic and hypoxic zones (on average 4.5 mmol m−2 d−1), but declined to 1.3 mmol m−2 d−1 in bottom
waters with oxygen concentrations below 20 μmol L−1. Measurements
and modeling of porewater profiles indicated that reoxidation of reduced
compounds played only a minor role in diffusive oxygen uptake under the
different oxygen conditions, leaving the major fraction to aerobic
degradation of organic carbon. Remineralization efficiency decreased from
nearly 100 % in the oxic zone, to 50 % in the oxic–hypoxic zone, to 10 %
in the hypoxic–anoxic zone. Overall, the faunal remineralization rate was
more important, but also more influenced by fluctuating oxygen
concentrations, than microbial and geochemical oxidation processes. |
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