TY - JOUR T1 - From In Situ to satellite observations of pelagic Sargassum distribution and aggregation in the Tropical North Atlantic Ocean A1 - Ody,Anouck A1 - Thibaut,Thierry A1 - Berline,Léo A1 - Changeux,Thomas A1 - André,Jean-Michel A1 - Chevalier,Cristèle A1 - Blanfuné,Aurélie A1 - Blanchot,Jean A1 - Ruitton,Sandrine A1 - Stiger-Pouvreau,Valerie A1 - Connan,Solène A1 - Grelet,Jacques A1 - Aurelle,Didier A1 - Guéné,Mathilde A1 - Bataille,Hubert A1 - Bachelier,Celine A1 - Guillemain,Dorian A1 - Schmidt,Natascha A1 - Fauvelle,Vincent A1 - Guasco,Sophie A1 - Ménard,Frédéric AD - Aix-Marseille Univ., Université de Toulon, CNRS, IRD, MIO UM 110, Marseille, France AD - Université de Bretagne Occidentale (UBO), Institut Universitaire Européen de la Mer (IUEM), LEMAR UMR 6539, Technopôle Brest-Iroise, Plouzané, France AD - IRD DR-OUEST, US191 IMAGO, Technopole de Brest-Iroise—Site de la Pointe du Diable, Plouzané, France AD - Université des Antilles, UMR BOREA, Campus de Fouillole, BP 592, Pointe-à-Pitre, Guadeloupe, France AD - IRD, IRD-Images, Marseille, France AD - Aix Marseille Univ, CNRS, IRD, IRSTEA, OSU PYTHEAS, Marseille, France UR - https://archimer.ifremer.fr/doc/00514/62609/ DO - 10.1371/journal.pone.0222584 N2 - The present study reports on observations carried out in the Tropical North Atlantic in summer and autumn 2017, documenting Sargassum aggregations using both ship-deck observations and satellite sensor observations at three resolutions (MSI-10 m, OLCI-300 m, VIIRS-750 m and MODIS-1 km). Both datasets reported that in summer, Sargassum aggregations were mainly observed off Brazil and near the Caribbean Islands, while they accumulated near the African coast in autumn. Based on in situ observations, we propose a five-class typology allowing standardisation of the description of in situ Sargassum raft shapes and sizes. The most commonly observed Sargassum raft type was windrows, but large rafts composed of a quasi-circular patch hundreds of meters wide were also observed. Satellite imagery showed that these rafts formed larger Sargassum aggregations over a wide range of scales, with smaller aggregations (of tens of m2 area) nested within larger ones (of hundreds of km2). Match-ups between different satellite sensors and in situ observations were limited for this dataset, mainly because of high cloud cover during the periods of observation. Nevertheless, comparisons between the two datasets showed that satellite sensors successfully detected Sargassum abundance and aggregation patterns consistent with in situ observations. MODIS and VIIRS sensors were better suited to describing the Sargassum aggregation distribution and dynamics at Atlantic scale, while the new sensors, OLCI and MSI, proved their ability to detect Sargassum aggregations and to describe their (sub-) mesoscale nested structure. The high variability in raft shape, size, thickness, depth and biomass density observed in situ means that caution is called for when using satellite maps of Sargassum distribution and biomass estimation. Improvements would require additional in situ and airborne observations or very high-resolution satellite imagery. Y1 - 2019/09 PB - Public Library of Science (PLoS) JF - Plos One SN - 1932-6203 VL - 14 IS - 9 ID - 62609 ER -