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| Titel |
Spectroscopic detection of a ubiquitous dissolved pigment degradation product in subsurface waters of the global ocean |
| VerfasserIn |
R. Röttgers, B. P. Koch |
| 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 ; 9, no. 7 ; Nr. 9, no. 7 (2012-07-13), S.2585-2596 |
| Datensatznummer |
250007187
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| Publikation (Nr.) |
 copernicus.org/bg-9-2585-2012.pdf |
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| Zusammenfassung |
| Measurements of light absorption by chromophoric dissolved organic matter
(CDOM) from subsurface waters of the tropical Atlantic and Pacific Oceans
showed a distinct absorption shoulder at 410–415 nm. This indicates an
underlying absorption of a pigment whose occurrence is partly correlated
with the apparent oxygen utilization (AOU) but also found in the deep
chlorophyll maximum. A similar absorption maximum at ~415 nm was also
found in the particulate fraction of samples taken below the surface mixing
layer and is usually attributed to absorption by respiratory pigments of
heterotrophic unicellular organisms. In our study, fluorescence measurements
of pre-concentrated dissolved organic matter (DOM) samples from 200–6000 m confirmed a previous study suggesting that the absorption at ~415 nm was related to
fluorescence at 650 nm in the oxygen minimum zone. The absorption
characteristics of this fluorophore was examined by fluorescence
emission/excitation analysis and showed a clear excitation maximum at 415 nm
that could be linked to the absorption shoulder in the CDOM spectra. The
spectral characteristics of the substance found in the dissolved and
particulate fraction did not match with those of chlorophyll a degradation
products (as found in a sample from the sea surface) but can be explained by
the occurrence of porphyrin pigments from either heterotrophs or autotrophs.
Combining the observations of the fluorescence and the 415-nm absorption
shoulder suggests that there are high concentrations of a pigment
degradation product in subsurface DOM of all major oceans. Most
pronouncedly we found this signal in the deep chlorophyll maximum and the
oxygen minimum zone of tropical regions. The origin, chemical nature,
turnover rate, and fate of this molecule is so far unknown. |
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