As one of the consequences of variation of glacier mass balance, length and size, additional areas become ice-free and subjected to weathering and soil formation, whose processes are influenced by the extreme conditions, heterogeneous topography and lack of nutrients of the glacier forelands. Cryoconite holes are water-filled depressions formed on the glacier surface when soil/sediment particles absorb more solar radiation than the surrounding ice. Ice melt forms channels that could flush the cryoconite holes and transport nutrients and microorganisms. Compared with the other glacial habitats, cryoconite holes are thought to contain the highest level of biodiversity (Foreman et al., 2007). Microbial survival and activity in such ecosystems is based on physiological adaptation mechanisms enabling organisms to be active at permanently low temperature. Recent discoveries of new bacteria species in cryoconites (Margesin et al., 2012; Zhang et al., 2011; 2012) demonstrate how these peculiar ecosystems provide a unique habitat with specific structure and functions. In this study we assessed prokaryotic communities in terms of abundance and diversity and investigated bio-chemical characteristics of organo-mineral debris found in the proglacial area of the Indren glacier (NW Alps, Italy). Samples were collected in 2004 and 2008 at an elevation of 3300 m asl, in an area covered by granular deposits, likely of cryoconitic origin. Aim of the study was to understand the role of Bacteria and Archaea in fixation, stabilization and evolution of C in organo-mineral debris and to verify the compatibility of the composition of prokaryotic communities with species composition retrieved in cryoconite samples from literature. Denaturing gradient gel electrophoresis (DGGE) and quantitative real-time PCR (qPCR) approaches were used to assess respectively the molecular diversity and abundance of Bacteria and Archaea. The biochemical characterization of the organic fraction revealed the prevalence of compounds derived from microbial cell structures and by-products of microbial activity, weakly associated to mineral components. These organo-minerals deposits seem to provide a habitat for a phylogenetically diverse group of Bacteria while Archaea are abundant but less diverse. Comparison of bacterial species composition among replicates of organo-mineral debris indicates the coexistence of different ecological niches where metabolic diversity could drive ecosystem nutrient cycling and organo-mineral stabilization.
Prokaryotic communities in organo-mineral deposits in a glacier foreland of the Alps
GORRA, ROBERTA;CELI, Luisella Roberta;FREPPAZ, Michele
2012-01-01
Abstract
As one of the consequences of variation of glacier mass balance, length and size, additional areas become ice-free and subjected to weathering and soil formation, whose processes are influenced by the extreme conditions, heterogeneous topography and lack of nutrients of the glacier forelands. Cryoconite holes are water-filled depressions formed on the glacier surface when soil/sediment particles absorb more solar radiation than the surrounding ice. Ice melt forms channels that could flush the cryoconite holes and transport nutrients and microorganisms. Compared with the other glacial habitats, cryoconite holes are thought to contain the highest level of biodiversity (Foreman et al., 2007). Microbial survival and activity in such ecosystems is based on physiological adaptation mechanisms enabling organisms to be active at permanently low temperature. Recent discoveries of new bacteria species in cryoconites (Margesin et al., 2012; Zhang et al., 2011; 2012) demonstrate how these peculiar ecosystems provide a unique habitat with specific structure and functions. In this study we assessed prokaryotic communities in terms of abundance and diversity and investigated bio-chemical characteristics of organo-mineral debris found in the proglacial area of the Indren glacier (NW Alps, Italy). Samples were collected in 2004 and 2008 at an elevation of 3300 m asl, in an area covered by granular deposits, likely of cryoconitic origin. Aim of the study was to understand the role of Bacteria and Archaea in fixation, stabilization and evolution of C in organo-mineral debris and to verify the compatibility of the composition of prokaryotic communities with species composition retrieved in cryoconite samples from literature. Denaturing gradient gel electrophoresis (DGGE) and quantitative real-time PCR (qPCR) approaches were used to assess respectively the molecular diversity and abundance of Bacteria and Archaea. The biochemical characterization of the organic fraction revealed the prevalence of compounds derived from microbial cell structures and by-products of microbial activity, weakly associated to mineral components. These organo-minerals deposits seem to provide a habitat for a phylogenetically diverse group of Bacteria while Archaea are abundant but less diverse. Comparison of bacterial species composition among replicates of organo-mineral debris indicates the coexistence of different ecological niches where metabolic diversity could drive ecosystem nutrient cycling and organo-mineral stabilization.
I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
