Biogeosciences, 7, 4083–4103, 2010 www.biogeosciences.net/7/4083/2010/ doi:10.5194/bg-7-4083-2010 Author(s) 2010. CC Attribution 3.0 License.
Biogeosciences
Fluorescence and absorption properties of chromophoric dissolved organic matter (CDOM) in coastal surface waters of the northwestern Mediterranean Sea, inuence of the Rh ne River o
J. Para1,2 , P. G. Coble3 , B. Charri` re1,2 , M. Tedetti1,2 , C. Fontana4,5 , and R. Semp r 1 e e e
1 Universit e
de la M diterran e, LMGEM, Centre d'Oc anologie de Marseille, Case 901, 13288 Marseille Cedex 9, France e e e UMR 6117, LMGEM, Case 901, 13288 Marseille Cedex 9, France 3 College of Marine Science, University of South Florida, 140 7th Avenue, St. Petersburg, Florida 33701, USA 4 Universit de la M diterran e, LOPB, Centre d'Oc anologie de Marseille, UMR 6535, Station Marine d'Endoume, e e e e Chemin Batterie des Lions, 13007 Marseille, France 5 CNRS/INSU, UMR 6535, LOPB, Centre d'Oc anologie de Marseille, Station Marine d'Endoume, Chemin Batterie e des Lions, 13007 Marseille, France
2 CNRS/INSU,
Received: 28 June 2010 – Published in Biogeosciences Discuss.: 22 July 2010 Revised: 7 December 2010 – Accepted: 17 December 2010 – Published: 23 December 2010
Abstract. 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 uorescence). The annual mean value of surface CDOM absorption coefcient at 350 nm [aCDOM (350)] was very low (0.10 ± 0.02 m1 ) in comparison to values usually found in coastal waters, and no signicant seasonal trend in aCDOM (350) could be determined. By contrast, the spectral slope of CDOM absorption (SCDOM ) was signicantly higher (0.023 ± 0.003 nm1 ) in summer than in fall and winter periods (0.017 ± 0.002 nm1 ), reecting either CDOM photobleaching or production in surface waters during stratied sunny periods. The CDOM uorescence, 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 uorescence (peak C; 0.34–2.99 QSU) remained very low. This reected a dominance of relatively fresh material from biological origin within the CDOM uorescent pool. At the end of summer, surface CDOM uorescence was very low and strongly blue shifted, reinforcing the hypothesis of CDOM photobleaching. Our results suggested that unusual Rh ne o

下一页