Pelagic protist (including phytoplankton) abundance and biodiversity data collected from the water column and water filled voids inside ridges during MOSAiC legs 2 to 4 in 2019/2020

The data has been collected during the the year-long drift expedition "Multidisciplinary drifting Observatory for the Study of Arctic Climate" (MOSAiC) from September 2019 to September 2020 on research vessel Polarstern. The samples were collected with Niskin bottles attached to a CTD rosette, an Apstein net with 20 µm mesh size, a hand pump or a pump mounted on a ROV. The samples were preserved using a few drops of Lugol and hexamethylenetetramine-buffered formalin at a final concentration of 1%. The samples were collected with Niskin bottles attached to a CTD rosette at the following depths: 5, 10, 30, 60, 90 m and deep chlorophyll max (DCM). Protists were identified and counted with light microscopy using the Utermöhl method and the result are given as cells per liter (cells/L) called Abundance.