**8. Conclusion**

examined using analyses of 16S rRNA genes [51]. In these studies, it was observed that the bacterial community structure depends on the type of snow deposition. However, the most interesting fact, from the point of view of monitoring the state of conservation of the glacier is that slush (the product of decomposition of snow when it melts) contains lineages of bacteria completely different from those of freshly fallen snow, which implies a change in the compo-

Other studies carried out in Greenland demonstrated that the phylogenetic composition of the microbial communities was different within the snow layers [75]. Proteobacteria, Bacteroidetes, and Cyanobacteria dominated in the middle and top snow layers, although Actinobacteria and Firmicutes were also abundant. In the deepest snow layer, large percentages of Firmicutes and Fusobacteria were found [75]. Large numbers of eukaryotic chloroplasts belonging to Streptophyta and Chlorophyta were also observed, demonstrating that microeukaryotes were also present in snow. Cyanobacteria and algae were almost exclusively found in the top and middle layers of the snow pack which are probably feeding the hetero-

Some reports have demonstrated that the composition of snow microbial communities depends on the proximity to the sea [76]. In glacier snow, typical species of marine environments such as the Alphaproteobacteria have been found in samples from Antarctica, although

Microbial communities in glacier fronts have been especially studied in the Antarctic Peninsula which is among the regions with the fastest warming rates, and where regional

Archaeal and bacterial 16S rRNA gene sequences obtained from soil samples collected in the Wanda Glacier forefield showed that the diversity and richness were surprisingly high, and that communities were dominated by Proteobacteria, Bacteroidetes, and Euryarchaeota, with many archaeal and bacterial phylotypes yet unclassified (**Figure 6(B)**). Some of the phylotypes found were also related to marine microorganisms, indicating the importance of the marine environment as a source of colonizers for these recently deglaciated environments [6]. Concerning microbial abundance, some examples have been published. In Greenland glacier

cells/ml, it has been reported [77].

It has been published that microbial abundance in an Antarctic glacier (Ecology Glacier) forefield is increased along several sampling points from the glacier front to the farther outskirts of the glacier [71]. The same effect has been observed in the Peruvian Andes glaciers, where

Regarding diversity, new soils from recently deglaciated soils are colonized by a diverse community of microorganisms during the first years following glacial retreat. Taxonomically microorganisms from Ecology Glacier forefield [71] belonged to the alpha, beta, and gamma

abundances of Cyanobacteria and Diatoms increased over the time of succession [62].

climate change has been linked to an increase in the mean rate of glacier retreat [6].

sition of the community structure that is post-depositional.

trophic members of the microbial communities.

**7.2. Glacier front**

116 Glacier Evolution in a Changing World

fronts, between 6 and 30 × 107

**7.3. Fore field**

Bacteroidetes and Cyanobacteria are also present [76].

In summary, glaciers are retreating in many areas of the world due to global warming, and many of them will be severely affected or will disappear in a few years. Glaciers are unique biomes dominated by microbial communities which maintain active biochemical routes. Their metabolic activity plays an important role in glaciers, mainly carrying out key processes in the development of soil, changing biogeochemical cycling, altering the composition of runoff waters and facilitating plant and animal colonization when glaciers have ultimately retired. These processes impact the planet not only locally but also globally. Microorganisms are perfectly adapted to their harsh environment and are very susceptible to environmental changes. Colonization and primary succession of a recently deglaciated area implies that the abundance of microorganisms increases along deglaciated areas. Yet, at the same time, the diversity of microbial populations changes. In many cases, the number of different species may be lower than it is in the glacier. Thus, abundance and distribution of microorganisms can be considered indicative of the conservation status of glaciers, because alterations in their abundance and distribution depend on glacier conditions. Microbial ecology can be a tool for monitoring the biological change that happens in retreat glaciers.
