Phytoplankton species analysis from Atlantic Ocean surface water samples collected during DY110 (AMT29) in October-November 2019.

This dataset contains phytoplankton abundances, cell abundances per taxa (number of cells per Litre), also expressed as Carbon concentration, (µg Carbon per Litre), collected in surface samples along a transect on the Atlantic Ocean, during the 29th Atlantic Meridional Transect cruise (AMT29/DY110). The samples were collected between October and November 2019 at 55 CTD stations, at 2 m or 5 m depth between 50° N and 42° S. Samples were fixed and observations were carried out with a Zeiss Axiovert 200 inverted microscope. Cells > 10 µm were counted in a 50 mL chamber, following the Utermöhl method (Utermöhl, 1958). Species from the following divisions/classes were identified and counted from Lugol’s-fixed samples: Bacillaryophyceae (Diatoms), Dinophyceae, separated into Autotrophic (ADinos) and Heterotrophic Dinoflagellates (HDinos), Prasinophyceae; furthermore the genus Phaeocystis and filamentous cyanobacteria belonging to three genera were also quantified. The cell carbon content was obtained mainly from the AMT database published by Sal et al. (2013). For species absent in the AMT database, biovolume was converted to cell carbon using the conversion factors presented by Menden-Deuer and Lessard (2000). Species biovolume was calculated either from measurements using photographic images taken during this study, using the geometrical forms indicated by Hillebrand et al. (1999), Sun and Liu (2003), and Olenina et al. (2006), or if not possible, from the species biovolume indicated by Olenina et al. (2006).