Abstract
The Antarctic continent is widely considered to be one of the most hostile biological habitats on Earth. Despite extreme environmental conditions, the ice-free areas of the continent, which constitute some 0.44% of the total continental land area, harbour substantial and diverse communities of macro-organisms and especially microorganisms, particularly in the more “hospitable” maritime regions. In the more extreme non-maritime regions, exemplified by the McMurdo Dry Valleys of South Victoria Land, nutrient cycling and ecosystem servicing processes in soils are largely driven by microbial communities. Nitrogen turnover is a cornerstone of ecosystem servicing. In Antarctic continental soils, specifically those lacking macrophytes, cold-active free-living diazotrophic microorganisms, particularly Cyanobacteria, are keystone taxa. The diazotrophs are complemented by heterotrophic bacterial and archaeal taxa which show the genetic capacity to perform elements of the entire N cycle, including nitrification processes such as the anammox reaction. Here, we review the current literature on nitrogen cycling genes, taxa, processes and rates from studies of Antarctic soils. In particular, we highlight the current gaps in our knowledge of the scale and contribution of these processes in south polar soils as critical data to underpin viable predictions of how such processes may alter under the impacts of future climate change.
Highlights
Continental Antarctica is largely ice-covered, with limited coastal, montane and maritime ice-free areas [1]
There is a growing worldwide emphasis on large-scale biogeographic studies of soil microbial diversity. While such published studies in Antarctica are currently restricted to sub-regions of the continent, a number of continent-wide soil microbiology biogeographical surveys are currently underway, at least one of which includes samples recovered by the 20th December 2016–19th March 2017 Antarctic
Most of the surveys of N-cycling functional markers in Antarctic soils have focused on the core genes involved in N-fixation, nitrification and denitrification processes
Summary
Continental Antarctica is largely ice-covered, with limited coastal, montane and maritime ice-free areas (approx. 54,000 km, est. 0.44%) [1]. There is a growing worldwide emphasis on large-scale biogeographic studies of soil microbial diversity While such published studies in Antarctica are currently restricted to sub-regions of the continent (such as the McMurdo Dry Valleys [3] and the Antarctic Peninsula [7]), a number of continent-wide soil microbiology biogeographical surveys are currently underway, at least one of which includes samples recovered by the 20th December 2016–19th March 2017 Antarctic. The very limited data on N-processing rates in any of the different Antarctic soil habitats make it virtually impossible, at the current state of knowledge, to model the nitrogen turnover contributions to ecosystem services in any part of terrestrial Antarctica, with the consequence that an accurate baseline for future estimations of the effects of continental climate change is remote. We review the current state of knowledge of nitrogen processing in Antarctic soils (Figure 1), wMiictrhooargnaneimsmps h20a2s0i,s8,oxnFtOhRePcErEitRicRaElVgIaEpWs in our knowledge base
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