Phosphorus limits the growth of primary producers in recently deglaciated High Arctic soils (Ny-Ålesund, Svalbard)

We combined field observations and microcosm experiments on recently deglaciated proglacial soils from Midtre Lovénbreen, Svalbard. Geochemical analyses suggest stronger limitation by nitrogen (N) and phosphorus (P) than by carbon (C). To distinguish between N and P limitation, we caried out microcosm incubations. In +N+P microcosms there was a bloom of rapidly growing soil algae and predatory bacteria resulting in significant shifts in microbial community structure. Addition of P decreased the C:N ratio, changed the structure of the prokaryotic community, and increased the growth of soil algae, mosses, and N-fixing cyanobacteria. Overall, these results indicate that P availability limits the establishment of early microbial primary producers. Given the rapid deglaciation of High Arctic regions, these findings highlight the central role of P in structuring these emerging ecosystems.