Terrestrial ecosystem processes of Victoria Land, Antarctica

Rapid microbial response to the presence of an ancient relic in the Antarctic Dry Valleys

“…However, the bulk of Dry Valley biodiversity and biomass consists of edaphic bacteria 8,11,12 , as few other organisms can endure the region's extreme temperature and light regimes, high soil salt concentrations, near-negligible levels of organic C and N, and scarcity of liquid water 10,12 . It has been suggested that these soil microbial communities are principally sustained and structured by the location and distribution of legacy C sources in the form of ancient lake sediments [13][14][15][16] . Under this hypothesis, contemporary environmental conditions exert limited influence on community dynamics 13,15 , as microbial activity in the Dry Valleys has, until recently, been thought to be exceptionally low compared with temperate ecosystems 13,15 .…”

“…It has been suggested that these soil microbial communities are principally sustained and structured by the location and distribution of legacy C sources in the form of ancient lake sediments [13][14][15][16] . Under this hypothesis, contemporary environmental conditions exert limited influence on community dynamics 13,15 , as microbial activity in the Dry Valleys has, until recently, been thought to be exceptionally low compared with temperate ecosystems 13,15 . Activity is further restricted to brief periods during austral summers, when liquid water may be available in certain niche habitats [17][18][19] .…”

“…As a result, changes in soil ecology are believed to take place over centuries and even millennia 13,15 , despite the fact that no direct studies have been conducted on rates of change in microbial community structure and function. Instead, researchers studying Dry Valley soil ecosystems have used CO 2 efflux and rates of organic C turnover in soil as proxies for microbial activity, and as low activity rates ipso facto preclude changes in community structure, data showing low rates have been taken to indicate slow rates of change in microbial communities.…”

“…For example, Johnston and Vestal's study of Dry Valley cryptoendoliths 20 used the slow lipid C turnover rate (~20,000 years) to support the claim that they are the slowestgrowing communities on earth. Therefore, despite widespread acknowledgment of the susceptibility of Dry Valley microbial communities to seasonal variations in biological activity 15,[21][22][23] , no study has described or predicted rapid and sustained changes in community structures caused by contemporary environmental conditions.…”

“…More recent studies have shown that the Dry Valleys support a phylogenetically diverse group of microbes 12,24,25 , and a handful of these studies have speculated that these communities respond on much shorter, decadal timescales 15,19,21,26 . In this study we have compared soil beneath a seal carcass found in the Miers Valley, Victoria Land, Antarctica, with soils from nearby exposed control sites to characterize the physicochemical and biological modifications associated with the mummified seal.…”