“…Glaciers and ice sheets are shrinking rapidly as a consequence of climate warming, especially in the Arctic where the surface air temperature has increased twice the global average in the last two decades (Meredith et al., 2019). Accelerating glacier recession, inevitable in the coming decades (Bosson et al., 2019; Hugonnet et al., 2021; Zemp et al., 2019), is causing large and irreversible changes to Arctic ecosystems, including the loss of biodiversity and function associated with glacial habitats (Cauvy‐Fraunié & Dangles, 2019; Stibal et al., 2020) and the transition of vast areas of subglacial environment to proglacial habitats subject to rapid ecological succession (Bernasconi et al., 2011; Wojcik et al., 2021). While post‐glacial ecosystem development is largely dependent on allochthonous materials (Rime et al., 2016), the subglacial legacy is likely important as a “starter pack” containing labile crustal nutrients (Hawkings et al., 2014, 2016, 2020; Hatton et al., 2019; Urra et al., 2019), nitrogen (Lawson, Bhatia, et al., 2014; Martin et al., 2020), organic carbon (OC) substrates (Hood et al., 2009; Lawson, Wadham, et al., 2014; Stibal, Wadham, et al., 2012; Wadham et al., 2019), and microbial inocula (Bradley et al., 2016; Řeháková et al., 2010; Rime et al., 2016).…”