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Theses

Observer les coccolithophores de l'espace

Abstract : Coccoliths, in cells or detached, from coccolithophores are calcite plates with highly backscattering signal.Coccolithophore blooms are visible from space and are currently quantified by Calcite algorithm fromNASA applied to Ocean Color data. Coccoliths impact also the Suspended Particulate Matters (SPM) product from Ifremer, well established in the Northwest european continental shelf. Although these algorithms are independent, they are based on the same basic concepts, but Ifremer algorithm is more adaptable and allows to link up with other particles than coccoliths, as the resuspended matters or aggregates.Coccolithophore blooms identification over 18 years, from bay of Biscay to South Irelands has been established by a spectral method, allowing to discriminate coccoliths from SPM. Blooms follow the continental slope northward in connection with the seasonal variability of irradiance. The interannual variability observed indicates a slight decrease of blooms, with a very poor productive year in 2014.Data from PELGAS cruises in May in the Bay of Biscay highlight the strong correlation between SPM product and the in situ turbidity in coccolithophore blooms.This parameter can be considered a a good proxy for the blooms monitoring and for the description of their vertical structure. Hydrological in situ data show a stronger occurrence in less stratified environment, with lower temperatures and higher salinity.The sensitivity of the satellite to the presence of coccoliths has benn evaluated based on in situ observations from cruises in the Bay of Biscay and in Patagonia. This sensitivity is variable due to a lot of inherent factors, to the coccoliths/coccospheres proportion and to the taxonomic composition which has been rich in May 2016 in the Bay of Biscay.
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Submitted on : Tuesday, January 30, 2018 - 11:25:09 AM
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  • HAL Id : tel-01696232, version 1

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Laurie Perrot. Observer les coccolithophores de l'espace. Sciences de la Terre. Université de Bretagne occidentale - Brest, 2017. Français. ⟨NNT : 2017BRES0032⟩. ⟨tel-01696232⟩

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