The data sets originates from the weekly sampling events (MOSAiC time series) during the MOSAiC campaign. Water samples from the CTD/Rosette were taken and fixed in Hexamin- buffered Formalin. 50ml subsamples were counted using the Utermöhl method. Counts were carried out with a Zeiss inverted microscope. The data set comprises bulk parameters with cell abundances (as cells/l) for the most abundant protist groups. In addition cell numbers for the toxic pennate diatom are provided separately

The data file comprises a subset of count data from MOSAiC leg 3. A summary file provides cell totals for the main plankton groups. In addition, individual data for one pennate diatom genus (Pseudo-nitzschia) is also provided. The latter is a subset of the bulk data for pennate diatoms. The values are also included in the bulk data file. The data are used for a manuscript Hoppe et al. (submitted).