Glacial ice was for a long time considered only as an extremely stable, frigid and static environment. However, recent investigations showed that glacial ice and glaciers are much more dynamic at the microscale, as well as at the geomorphological level, than previously assumed. Particularly in polythermal glaciers, characterized by a warm core, quick seismic shifts can occur and cause displacements of cryokarst formations and glacial ice masses. Increased pressure at the base of the glaciers can generate subglacial ice melting. These waters, supplemented with supraglacial melt-waters and groundwater, soak rocks and sediments below the glacier and become enriched with local solutes and suspended sediments. When frozen together with the base of the glacier, they constitute the subglacial environment.
Until recently, subglacial environments were thought to be abiotic. However, recent studies revealed the existence of aerobic heterotrophic bacterial communities able to survive the dynamic processes of thawing and freezing. To our knowledge, until our investigations, there were no reports on the presence of fungi in subglacial ice. Given the known adaptive behaviour of many fungi to low water activity (aw) and a wide range of temperatures, we assumed that various types of ice can represent potential natural habitats for diverse halotolerant fungi. To evaluate this hypothesis, media with lowered aw and incubations at low and "normal" temperatures were chosen to provide a selective advantage for the recovery of culturable fungi from supra- and subglacial environments of four different polythermal Arctic glaciers (Svalbard, Norway).
The dominant taxons isolated were basidiomycetous and ascomycetous yeasts, melanized yeast-like fungi, mainly represented by the genera Cladosporium and
Correspondence to: Lorena Butinar University of Nova Gorica Laboratory for Environmental Research P.O.Box 301 SI-5001 Nova Gorica Slovenia E-mail: [email protected] Fax: +386-5-3315232 Tel: +386-53315296
Aureobasidium and different species of the genus Penicillium. The fungal counts detected in the subglacial samples were two orders of magnitude greater when compared with those recovered from supraglacial samples, mainly due to yeasts (with counts reaching 4 x 106 CFU L-1). Five ascomycetous and twenty-two basidiomycetous yeast species were isolated, including three new species. According to species diversity and abundance, the majority of species were assigned to the hymenomycetous yeasts (Filobasidium/Cryptococcus albidus taxa of the Tremellales). The stable core of the subglacial yeast communities were represented by Cr. liquefaciens, Rhodotorula mucilaginosa, Debaryomyces hansenii and Pichia guillermondii.
Among the isolated filamentous fungi the prevailing genus was Penicillium, with twenty-four different species being identified and a new species, P. svalbardense being described. The dominant species was P. crustosum, representing on the average half of all isolated strains from the studied glaciers. In contrast to yeasts, primarily associated with the clear subglacial ice, the highest counts for penicillia were obtained for debris-rich subglacial ice.
Enriched fungal populations in subglacial environments may represent a significant reservoir of biological activity with the potential to influence glacial melt-water composition, release of nitrogen and carbon in the polar environment and seeding of oceans with microbial life.
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