| Summary: | Plant, soil and algal rock scrape samples were taken in both April and August 2013 on Disko Island, West Greenland using a small trowel, placed into plastic bags, and subsequently transferred into glass vials for freeze drying and homogenisation. Samples were analysed for carbon isotopes (BGS, Keyworth) and compound-specific carbon isotopes (CUG, Wuhan) on fatty acid methyl esters (FAMEs) (prepared at Newcastle University). Analyses were completed as part of Mark A. Stevenson's PhD research while based at the University of Nottingham, UK (Stevenson, 2017, http://eprints.nottingham.ac.uk/46579). Bulk δ¹³C was analysed on acidified samples using a Costech ECS4010 elemental analyser (EA) coupled to a VG Triple Trap and a VG Optima dual-inlet mass spectrometer. Compound-specific δ¹³C on C~28:0~ fatty acid methyl ester (FAME) were analysed using a Thermo Finnigan Trace GC coupled to a Thermo Finnigan Delta Plus XP isotope ratio mass spectrometer using a combustion interface (GC-C-IRMS) according to conditions in Huang et al. (2018; doi:10.1038/s41467-018-03804-w). Acknowledgements Mark Stevenson gratefully acknowledges the receipt of a NERC/ESRC studentship (ES/J500100/1). We acknowledge grants IP-1393-1113 & IP-1516-1114 from the NERC Isotope Geosciences laboratory (NIGL) for the analysis of δ¹³C~org~ & C/N ratios on sediment, soil and plant samples. Lipid analyses were funded by the Freshwater Biological Association's 2015 Gilson Le Cren Memorial Award to Mark Stevenson. We thank Teresa Needham, Christopher Kendrick, Julie Swales, Ian Conway, Graham Morris, Bernard Bowler, Paul Donohoe, Qingwei Song and Jiantao Xue for technical support. Financial support for fieldwork was awarded via the INTERACT transnational access scheme (grant agreement No 262693) under the European Community's Seventh Framework Programme and UK RI NERC grant NE/K000276/1. Logistical support is acknowledged from University of Copenhagen Arktisk Station including Ole Stecher, Kjeld Mølgaard and Erik Wille.
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