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| Titel |
Fluorescence and absorption properties of chromophoric dissolved organic matter (CDOM) in coastal surface waters of the northwestern Mediterranean Sea, influence of the Rhône River |
| VerfasserIn |
J. Para, P. G. Coble, B. Charrière, M. Tedetti, C. Fontana, R. Sempéré |
| 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 ; 7, no. 12 ; Nr. 7, no. 12 (2010-12-23), S.4083-4103 |
| Datensatznummer |
250005110
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| Publikation (Nr.) |
 copernicus.org/bg-7-4083-2010.pdf |
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| Zusammenfassung |
| Seawater samples were collected monthly in surface waters (2 and 5 m depths)
of the Bay of Marseilles (northwestern Mediterranean Sea; 5°17'30" E,
43°14'30" N) during one year from November 2007 to December 2008 and
studied for total organic carbon (TOC) as well as chromophoric dissolved
organic matter (CDOM) optical properties (absorbance and fluorescence). The
annual mean value of surface CDOM absorption coefficient at 350 nm
[aCDOM(350)] was very low (0.10 ± 0.02 m−1) in comparison to
values usually found in coastal waters, and no significant seasonal trend in
aCDOM(350) could be determined. By contrast, the spectral slope of CDOM
absorption (SCDOM) was significantly higher (0.023 ± 0.003 nm−1)
in summer than in fall and winter periods (0.017 ± 0.002 nm−1),
reflecting either CDOM photobleaching or production in surface
waters during stratified sunny periods. The CDOM fluorescence, assessed
through excitation emission matrices (EEMs), was dominated by protein-like
component (peak T; 1.30–21.94 QSU) and marine humic-like component
(peak M; 0.55–5.82 QSU), while terrestrial humic-like fluorescence
(peak C; 0.34–2.99 QSU) remained very low. This reflected a
dominance of relatively fresh material from biological origin within the
CDOM fluorescent pool. At the end of summer, surface CDOM fluorescence was
very low and strongly blue shifted, reinforcing the hypothesis of CDOM
photobleaching. Our results suggested that unusual Rhône River plume
eastward intrusion events might reach Marseilles Bay within 2–3
days and induce local phytoplankton blooms and subsequent fluorescent CDOM
production (peaks M and T) without adding terrestrial fluorescence
signatures (peaks C and A). Besides Rhône River plumes, mixing events of
the entire water column injected relative aged (peaks C and M) CDOM from the
bottom into the surface and thus appeared also as an important source of
CDOM in surface waters of the Marseilles Bay. Therefore, the assessment of
CDOM optical properties, within the hydrological context, pointed out
several biotic (in situ biological production, biological production within
Rhône River plumes) and abiotic (photobleaching, mixing) factors
controlling CDOM transport, production and removal in this highly urbanized
coastal area. |
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