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Photobleaching as a factor controlling spectral characteristics of chromophoric dissolved organic matter in open ocean

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Title: Photobleaching as a factor controlling spectral characteristics of chromophoric dissolved organic matter in open ocean
Authors: Yamashita, Youhei Browse this author →KAKEN DB
Nosaka, Yuichi Browse this author
Suzuki, Koji Browse this author →KAKEN DB
Ogawa, Hiroshi Browse this author
Takahashi, Kazutaka Browse this author
Saito, Hiroaki Browse this author →KAKEN DB
Issue Date: 12-Nov-2013
Publisher: Copernicus Gesellschaft mbh
Journal Title: Biogeosciences
Volume: 10
Issue: 11
Start Page: 7207
End Page: 7217
Publisher DOI: 10.5194/bg-10-7207-2013
Abstract: 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 (S-R); 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.
Rights: © Author(s) 2013. This work is distributedunder the Creative Commons Attribution 3.0 License.
http://creativecommons.org/licenses/by/3.0/
Relation: http://www.biogeosciences.net/10/7207/2013/bg-10-7207-2013.html
Type: article
URI: http://hdl.handle.net/2115/54141
Appears in Collections:環境科学院・地球環境科学研究院 (Graduate School of Environmental Science / Faculty of Environmental Earth Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 山下 洋平

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