We acknowledge Captain Knowledge Bengu and the crew of the R/V SA Agulhas II, and Chief Scientists Hermann Luyt, Marcello Vichi, and Thomas Ryan-Keogh. We thank Tahlia Henry for CTD operations and CTD and SDS data processing. We are grateful to the students from the Cape Peninsula University of Technology for help with sample collection and analysis of chl-a samples. We thank Sedick Gallie for his assistance with sampling and for conducting the microscope counts, and Raquel Flynn, Mishka Rawatlal, and Raymond Roman for assistance with nutrient analyses. We acknowledge the Flow Cytometry Core Facility at the University of Cape Town (UCT) and the efforts of Ian Newton at the Stable Light Isotope Laboratory (UCT). This work was supported by the South African Departments of Forestry, Fisheries, and Environment (formerly Environmental Affairs) and Science and Innovation (DSI), and the National Research Foundation (NRF) through the South African National Antarctic Program (SANAP; 110732 to K.E.A and 105539, 110735, and 129232 to S.E.F.), Equipment-related Travel and Training Grant (118615 to K.E.A.), Competitive Support for Rated Researchers Grant (111716 to K.E.A.), and Incentive Fund (115335 to S.E.F.). S.S., M.M., K.A.M.S., and J.M.B. acknowledge funding from the NRF through postgraduate scholarships (120105, 112380, 113193, and 108757, respectively). S.S. was partially supported by a UCT Vice-Chancellor Research Scholarship and M.M. by the UCT Harry Crossley Foundation Research Fellowship. S.E.F. and K.E.A. acknowledge the support of the UCT Vice-Chancellor Future Leaders 2030 programme. S.E.F. acknowledges an African Academy of Sciences/Royal Society FLAIR fellowship and K.E.A. acknowledges support from UCT through a University Research Council Launching Grant and a University Equipment Committee Grant. We further acknowledge the support of the DSI Biogeochemistry Research Infrastructure Platform (BIOGRIP).

Nutrient data from underway (surface, ~7 m) and CTD (surface only, ~10 m) samples. Nutrients include ammonium, nitrate, nitrite, urea, phosphate, and silicate concentrations. Particulate organic nitrogen and carbon concentrations, chlorophyll-a concentrations, inorganic carbon uptake rates, and nitrogen (nitrate, ammonium, urea) uptake rates are included - all for two size classes: >0.3 microns and >2.7 microns. Ammonium oxidation rates are also provided. Plankton abundances are provided for various groups (microplankton enumerated with microscopy and nano- and picoplankton enumerated using flow cytometry). Cruise: 28 June - 13 July 2017; R/V SA Agulhas II (VOY025); Cape Town to the Marginal Ice Zone; WOCE IO6 line.