Abstract
Understanding the environmental factors that shape microbial communities is crucial, especially in extreme environments, like Antarctica. Two main forces were reported to influence Antarctic soil microbes: birds and plants. Both birds and plants are currently undergoing relatively large changes in their distribution and abundance due to global warming. However, we need to clearly understand the relationship between plants, birds and soil microorganisms. We therefore collected rhizosphere and bulk soils from six different sampling sites subjected to different levels of bird influence and colonized by Colobanthus quitensis and Deschampsia antarctica in Admiralty Bay, King George Island, Maritime Antarctic. Microarray and qPCR assays targeting 16S rRNA genes of specific taxa were used to assess microbial community structure, composition and abundance and analyzed with a range of soil physico-chemical parameters. The results indicated significant rhizosphere effects in four out of the six sites, including areas with different levels of bird influence. Acidobacteria were significantly more abundant in soils with little bird influence (low nitrogen) and in bulk soil. In contrast, Actinobacteria were significantly more abundant in the rhizosphere of both plant species. At two of the sampling sites under strong bird influence (penguin colonies), Firmicutes were significantly more abundant in D. antarctica rhizosphere but not in C. quitensis rhizosphere. The Firmicutes were also positively and significantly correlated to the nitrogen concentrations in the soil. We conclude that the microbial communities in Antarctic soils are driven both by bird and plants, and that the effect is taxa-specific.
Highlights
Deschampsia antarctica Desv. (Poaceae) and Colobanthus quitensis (Kunth) Bartl. (Caryophyllaceae) are the only two native vascular plants in Antarctica
In the Maritime Antarctic region, this increase in temperature has led to the thaw of glaciers, that exposed new areas of land [3], which could further increased the distribution of vascular plants [4]
A recent study showed, using 16S rRNA gene pyrosequencing, that the microbial communities associated with the rhizospheres of D. antarctica and C. quitensis did not differ significantly [11]
Summary
Deschampsia antarctica Desv. (Poaceae) and Colobanthus quitensis (Kunth) Bartl. (Caryophyllaceae) are the only two native vascular plants in Antarctica. (Caryophyllaceae) are the only two native vascular plants in Antarctica Both species are widespread, usually growing together and well adapted for life in the coastal Maritime Antarctic [1]. A considerable increase in distribution and abundance of D. antarctica and C. quitensis in the western Antarctic has been reported and interpreted as a response to more favorable growing and reproductive conditions [2]. Several authors have reported that this interaction selects for specific microbial communities in the rhizosphere, the portion of soil that is directly influenced by roots, producing the ‘‘rhizosphere effect’’ [6,7,8]. A recent study showed, using 16S rRNA gene pyrosequencing, that the microbial communities associated with the rhizospheres of D. antarctica and C. quitensis did not differ significantly [11]. This study did not compare bulk and rhizosphere soil, and it is still not known what level of influence vascular plants exert on Antarctic soil microorganisms
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