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| Titel |
Photobleaching as a factor controlling spectral characteristics of chromophoric dissolved organic matter in open ocean |
| VerfasserIn |
Y. Yamashita, Y. Nosaka, K. Suzuki, H. Ogawa, K. Takahashi, H. Saito |
| 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. 11 ; Nr. 10, no. 11 (2013-11-12), S.7207-7217 |
| Datensatznummer |
250085409
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| Publikation (Nr.) |
 copernicus.org/bg-10-7207-2013.pdf |
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| Zusammenfassung |
| Chromophoric dissolved organic matter (CDOM) ubiquitously occurs in marine
environments and plays a significant role in the marine biogeochemical
cycles. Basin scale distributions of CDOM have recently been surveyed in the
global ocean and indicate that quantity and quality of oceanic CDOM are
mainly controlled by in situ production and photobleaching. However, factors
controlling the spectral parameters of CDOM in the UV region, i.e., spectral
slope of CDOM determined at 275–295 nm (S275–295) and the ratio of two
spectral slope parameters (SR); the ratio of S275–295 to
S350–400, have not been well documented. To evaluate the factor
controlling the spectral characteristics of CDOM in the UV region in the open
ocean, we determined the quantitative and qualitative characteristics of
CDOM in the subarctic and subtropical surface waters (5–300 m) of the
western North Pacific. Absorption coefficients at 320 nm in the subarctic
region were higher than those in the subtropical region throughout surface
waters, suggesting that magnitudes of photobleaching were different between
the two regions. The values of S275–295 and SR were also higher in
the subtropical region than the subarctic region. The dark microbial
incubation showed biodegradation of DOM little affected S275–295, but
slightly decreased SR. On the other hand, increases in S275–295 and
relative stableness of SR were observed during photo-irradiation
incubations respectively. These experimental results indicated that
photobleaching of CDOM mainly induced qualitative differences in CDOM at UV
region between the subarctic and subtropical surface waters. The results of
this study imply that S275–295 can be used as a tracer of
photochemical history of CDOM in the open ocean. |
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