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Publication MIO : Cécile Dupouy (MIO), Robert Frouin, Marc Tedetti (MIO), Morgane Maillard (MIO), Martine Rodier, Fabien Lombard ,Lionel Guidi, Marc Picheral, Jacques Neveux, Solange Duhamel, Bruno Charrière, and Richard Sempéré (MIO) - Diazotrophic Trichodesmium impact on UV–Vis radiance and pigment composition in the western tropical South Pacific

Version imprimable de cet article

Received : 31 December 2017 – Discussion started : 15 January 2018
Revised : 25 June 2018 – Accepted : 10 July 2018 – Published : 30 August 2018

Cecile Dupouy and co-authors published in the Biogeosciences OUTPACE Special Issue in August 2018

The Trichodesmium contribution to total chlorophyll and zeaxanthin concentrations decreased from 60% in the Melanesian archipelago around New Caledonia and Vanuatu, with a maximum value of 7093 colonies m-3 as profiled by the UVP5 (2093-4715 trichomes L-1), down to 30 % in the vicinity of Fiji and to less than 20 % in the South Pacific Gyre where small Prochlorococcus dominated. Along the 4000 km OUTPACE transect in May 2015, inherent optical properties were largely influenced by Trichodesmium, with the absorption by Mycosporine-like Amino Acids at 330 nm well correlated to colony abundance, and a maximum backscattering at the surface. Apparent optical properties of tropical waters as measured with a UV-VIS SATLANTIC radiance indicated that radiance ratios were well related to Chla, but showed a lower absorption of UV-absorbing detritus and Chromophoric Dissolved Organic Matter at OUTPACE than at BIOSOPE. Radiance were also influenced by other variables than TChla, i.e., backscattering and accessory pigments on radiances at 490 and 565 nm, these wavelengths being used for detecting Trichodesmium with satellite ocean colour

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