The AWI-funded AMUST project aims at understanding at current and future controls of Arctic spring blooms and concurrent effects on biogeochemistry by combining experimental work with long-term monitoring in Kongsfjorden in spring. This dataset encompasses ecophysiological data (Chl-a, POC, C:N, 14C-based Primary Production) from surface water samples collected at the Ny-Ålesund jetty in February 2018, as well as two datasets of 24h continuous light measurements during in-situ incubations 0.2m below the sea surface.