FN Archimer Export Format PT J TI The many shades of red tides: Sentinel-2 optical types of highly-concentrated harmful algal blooms BT AF Gernez, Pierre Zoffoli, Maria Laura Lacour, Thomas HERNANDEZ FARINAS, Tania Navarro, Gabriel Caballero, Isabel Harmel, Tristan AS 1:1;2:2;3:3;4:4;5:5;6:5;7:6; FF 1:;2:;3:PDG-ODE-PHYTOX-PHYSALG;4:PDG-ODE-LITTORAL-LERN;5:;6:;7:; C1 Nantes Université, Institut des Substances et Organismes de la Mer, ISOMER, UR 2160, F-44000 Nantes, France Consiglio Nazionale delle Ricerche, Istituto di Scienze Marine (CNR-ISMAR), 00133, Rome, Italy Ifremer, PHYTOX, Laboratoire PHYSALG, F-44000 Nantes, France Ifremer, Laboratoire Environnement Ressources Normandie, Port en Bessin, France Consejo Superior de Investigaciones Científicas, Instituto de Ciencias Marinas de Andalucía, Puerto Real, Spain Magellium, 1 Rue Ariane, Ramonville-Saint-Agne, France C2 UNIV NANTES, FRANCE CNR ISMAR, ITALY IFREMER, FRANCE IFREMER, FRANCE CSIC, SPAIN MAGELLIUM, FRANCE SI NANTES PORT-EN-BESSIN SE PDG-ODE-PHYTOX-PHYSALG PDG-ODE-LITTORAL-LERN IN WOS Ifremer UPR copubli-france copubli-europe copubli-univ-france IF 13.5 TC 7 UR https://archimer.ifremer.fr/doc/00820/93193/99794.pdf https://archimer.ifremer.fr/doc/00820/93193/99795.docx https://archimer.ifremer.fr/doc/00820/93193/99796.xlsx https://archimer.ifremer.fr/doc/00820/93193/99797.docx LA English DT Article DE ;Phytoplankton;Ecology;Dinoflagellates;Cyanobacteria;Ciliate;mesodinium;noctiluca;lepidodinium;Pigments;REPHY;HAEDAT AB Harmful algal blooms (HABs) have severe environmental and economic impacts worldwide. Improving HAB detection is crucial because massive blooms are likely to increase in both frequency and amplitude in the next decades due to global warming and escalating coastal eutrophication. While satellite remote sensing has proved useful to detect red tides and support HAB monitoring, the discrimination of the dominant bloom-forming species is still a challenge, all the more as the observation of highly concentrated phytoplankton patches can be hampered by a too coarse spatial resolution. Moreover, the majority of HAB studies generally had a regional focus, and a limited number of species were separately documented so far. Here, we provide a broader perspective for red tides remote sensing to better resolve HAB optical and taxonomical diversity. The main objective of the present study was to identify how many optical bloom types could be recognized with the high spatial resolution Sentinel-2 (S2) satellite mission. For that purpose, an extensive database of massive, nearly monospecific blooms, both documented in situ and using synchronous S2 observation was compiled. More than 100 S2 images of various red tides were selected worldwide. Altogether, the S2 database covered the typical reflectance spectra of 27 red tide forming species. The remote-sensing reflectance of each red tide was analysed to evaluate S2 ability to distinguish the dominant species of the bloom. A hierarchical clustering analysis suggested that six optical bloom types could be identified: (1) surface accumulation of cyanobacteria or of green Noctiluca scintillans, (2) surface accumulation of red N. scintillans (a purely heterotrophic plankton devoid of chlorophyll a), (3) red tides of Mesodinium rubrum (a phycoerythrin-bearing ciliate), (4) green seawater discolorations of Lepidodinium chlorophorum (a dinoflagellate with unusual carotenoids), (5) blooms dominated by a dinoflagellate such as Prorocentrum, Gymnodinium, Lingulodinium polyedra, Gonyaulax or Alexandrium, and (6) brown tides dominated by a dinoflagellate (such as Karenia, Karlodinium veneficum, Protoceratium reticulatum, Margalefidinium polykrikoides, or Tripos fusus), a prymnesiophyte (Phaeocystis), or a pelagophyte (Aureococcus anophagefferens). While the results presented here are inherently limited by the concomitant availability of in situ and S2 observations, as well as by S2 spectral resolution, it is a step forward to an improved understanding of HAB bio-optical diversity. PY 2023 PD MAR SO Remote Sensing Of Environment SN 0034-4257 PU Elsevier BV VL 287 UT 000944332400001 DI 10.1016/j.rse.2023.113486 ID 93193 ER EF