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Biogeosciences An interactive open-access journal of the European Geosciences Union
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Volume 13, issue 11
Biogeosciences, 13, 3283-3303, 2016
https://doi.org/10.5194/bg-13-3283-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: Biogeochemical and biological response to a diazotroph bloom...

Biogeosciences, 13, 3283-3303, 2016
https://doi.org/10.5194/bg-13-3283-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 03 Jun 2016

Research article | 03 Jun 2016

Evolution of dissolved and particulate chromophoric materials during the VAHINE mesocosm experiment in the New Caledonian coral lagoon (south-west Pacific)

Marc Tedetti1, Lauriane Marie1,a, Rüdiger Röttgers2, Martine Rodier3, France Van Wambeke1, Sandra Helias1, Mathieu Caffin1, Véronique Cornet-Barthaux1, and Cécile Dupouy1,4 Marc Tedetti et al.
  • 1Aix Marseille Université, CNRS/INSU, Université de Toulon, IRD, Mediterranean Institute of Oceanography (MIO) UM 110, 13288, Marseille, France
  • 2Helmholtz-Zentrum Geesthacht, Centre for Materials and Coastal Research, Institute for Coastal Research, Remote Sensing, Geesthacht, Germany
  • 3IRD, Université de la Polynésie française, Institut Louis Malardé, Ifremer, UMR 241, Ecosystèmes Insulaires Océaniens (EIO), IRD Tahiti, PB 529, 98713 Papeete, Tahiti, French Polynesia
  • 4Institut de Recherche pour le Développement, AMU/CNRS/INSU, Université de Toulon, Mediterranean Institute of Oceanography (MIO) UM110, 98848 Noumea, New Caledonia
  • apresent address: Université de Bretagne Occidentale, LEMAR, UMR-CNRS 6539, Groupe Chimie Marine, Place N. Copernic, 29280 Plouzané, France

Abstract. In the framework of the VAHINE project, we investigated the spectral characteristics and the variability of dissolved and particulate chromophoric materials throughout a 23-day mesocosm experiment conducted in the south-west Pacific at the mouth of the New Caledonian coral lagoon (22°29.073S–166°26.905E) from 13 January to 4 February 2013. Samples were collected in a mesocosm fertilized with phosphate at depths of 1, 6 and 12m and in the surrounding waters. Light absorption coefficients of chromophoric dissolved organic matter (CDOM) [ag(λ)] and particulate matter [ap(λ)] were determined using a point-source integrating-cavity absorption meter (PSICAM), while fluorescent DOM (FDOM) components were determined from excitation-emission matrices (EEMs) combined with parallel factor analysis (PARAFAC). The evolutions of ag(λ) and ap(λ) in the mesocosm were similar to those of total chlorophyll a concentration, Synechococcus spp. and picoeukaryote abundances, bacterial production, particulate organic nitrogen and total organic carbon concentrations, with roughly a decrease from the beginning of the experiment to days 9–10, and an increase from days 9–10 to the end of the experiment. In the surrounding waters, the same trend was observed but the increase was much less pronounced, emphasizing the effect of the phosphate fertilization on the mesocosm's plankton community. Correlations suggested that both Synechococcus cyanobacteria and heterotrophic bacteria were strongly involved in the production of CDOM and absorption of particulate matter. The increase in phytoplankton biomass during the second part of the experiment led to a higher contribution of particulate material in the absorption budget at 442nm. The three FDOM components identified (tryptophan-, tyrosine- and ultraviolet C (UVC) humic-like fluorophores) did not follow the evolution of CDOM and particulate matter, suggesting they were driven by different production/degradation processes. Finally, the results of this work support the idea there is indirect coupling between the dynamics of N2 fixation and that of chromophoric material via the stimulation of Synechococcus bloom.

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In the framework of the VAHINE project, we investigated the spectral characteristics and the variability of dissolved and particulate chromophoric materials throughout a 23-day mesocosm experiment conducted in the south-west Pacific at the mouth of the New Caledonian coral lagoon. We found that the dynamics of CDOM and particulate matter absorption were strongly coupled with those of cyanobacteria Synechococcus spp. and bacterial production.
In the framework of the VAHINE project, we investigated the spectral characteristics and the...
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