Marked Succession of Cyanobacterial Communities Following Glacier Retreat in the High Arctic

Cyanobacteriaare important colonizers of recently deglaciatedproglacial soil but an in-depth investigation of cyanobacterial succession following glacier retreat has not yet been carried out. Here, we report on the successional trajectories of cyanobacterial communities in biological soil crusts(BSCs) along a 100-year deglaciationgradient in three glacier forefields in central Svalbard, High Arctic. Distance from the glacier terminuswas used as a proxy for soil age (years since deglaciation), and cyanobacterial abundance and community composition were evaluated by epifluorescence microscopy and pyrosequencingof partial 16S rRNA gene sequences, respectively. Succession was characterized by a decrease in phylotyperichness and a marked shift in community structure, resulting in a clear separation between early (10–20 years since deglaciation), mid (30–50 years), and late (80–100 years) communities. Changes in cyanobacterial community structurewere mainly connected with soil age and associated shifts in soil chemical composition (mainly moisture, SOC, SMN, K, and Na concentrations). Phylotypesassociated with early communities were related either to potentially novel lineages (< 97.5% similar to sequences currently available in GenBank) or lineages predominantly restricted to polar and alpine biotopes, suggesting that the initial colonization of proglacial soil is accomplished by cyanobacteriatransported from nearby glacial environments. Late communities, on the other hand, included more widely distributed genotypes, which appear to establish only after the microenvironment has been modified by the pioneering taxa.