This dataset contains fractional change in volumetric rates of alkaline phosphatase activity (APA) over time determined from near surface samples and APA rates determined during incubation experiments using zooplankton collected from the Subtropical North Atlantic Ocean. Samples used in the final analyses were collected on-board the RRS James Clark Ross cruise JR15007 (June to July 2016), RRS James Cook cruise JC150 (June to August 2017) and a previously published dataset from Dr Oliver Wurl using samples collected on-board Research Vessel Knorr 199-5, a US GEOTRACES cruise. The final analyses of the data and samples collected on-board cruise JC150 were funded as part of the Natural Environment Research Council (NERC) standard grant ‘Zinc, iron and phosphorus co-limitation in the Ocean (ZIPLOc)’ reference NE/N001079/1 lead by Principal Investigator Dr Claire Mahaffey and Co-Investigator Dr Clare Davis. The key aims were to assess if there was diurnal variability in APA, if zooplankton influenced APA in the surface ocean and quantified the diurnal variability in APA and the role of zooplankton in the surface ocean phosphate cycling to allow assessment that is more accurate and detection of future changes in ocean phosphate dynamics. Additional samples collected on cruise JR15007 were funded by NERC Grant NE/L004216/1 ‘A nutrient and carbon pump over mid-ocean ridges (RidgeMix) lead by Principal Investigator Professor Jonathan Sharples. The third party dataset provided by Dr Oliver Wurl were funded by the US National Science Foundation, Division of Ocean Sciences (Grants OCE 0929573 and OCE 0926092 to Professor G.Cutter).