Data were collected as part of the DiatomARCTIC project during the Multidisciplinary Arctic Program - Last Ice sampling campaign (82.576 N 62.471 W), 7-23 May, 2018. The bottom 10 cm of ice samples were collected during this time from neighbouring first-year and multi-year sea ice floes, from which the following parameters were determined: chlorophyll a, exopolymeric substances, ice algal taxonomic composition, oxygen-based net community production and bulk-ice nitrate, nitrite and phosphate concentrations. All samples were melted without dilution and were processed by K Campbell.

This work is a contribution to the Diatom ARCTIC project (NE/R012849/1; 03F0810A), part of the Changing Arctic Ocean program, jointly funded by the UKRI Natural Environment Research Council and the German Federal Ministry of Education (BMBF) and Fisheries and Oceans Canada (DFO) Science and the Marine Productivity Laboratory Program. The Multidisciplinary Arctic Program (MAP) - Last Ice is funded by Fisheries and Oceans Canada (DFO) Science in support of Tuvaijuittuq Marine Protected Area (MPA). Additional support was provided by Polar Continental Shelf Program (PCSP, Project 10718) and the Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Funds to CM and CHSR.