Scientists discover life beneath extreme environments

November 18th, 2008 - 3:24 pm ICT by ANI  

Washington, Nov 18 (ANI): Scientists have described apparently productive ecosystems in two places where life was not known before, under the Antarctic ice sheet, and above concentrated salt lakes beneath the Mediterranean.
The findings were described at a European Science Foundation and COST (European Cooperation in the field of Scientific and Technical Research) ”Frontiers of Science” meeting in Sicily.
In both cases, innumerable tiny microbes are fixing or holding onto quantities of organic carbon large enough to be significant in the global carbon cycle.
Brent Christner of Louisiana State University, in the US, told the conference about the microbes living within and beneath the ice on Antarctica.
In the last decade, scientists have discovered lakes of liquid water underneath the Antarctic ice sheet. So far, only 150 lakes are known, but this number will probably increase when the entire continent has been surveyed.
These lakes occur as a result of geothermal heat trapped by the thick ice, melting it from underneath, and the great pressure from the ice above, which lowers the melting point of water.
The largest subglacial lake, Lake Vostok, lies beneath the coldest place on the planet, where the temperature at the surface often falls below 60 degree Celsius.
Christner has examined microbial life in ice cores from Vostok and many other global locations.
While direct samples of water from subglacial Antarctic lakes have yet to be obtained, the lower 80m or so of the Vostok ice core represents lake water that progressively freezes onto the base as the ice sheet slowly traverses the lake.
“Microbial cell and organic carbon concentrations in this accreted ice are significantly higher than those in the overlying ice, which implies that the subglacial environment is the source,” said Christner.
Beneath the Mediterranean lurks a similar surprise.
Michail Yakimov, of the Institute of the Coastal Marine Environment, Messina, Italy, and his team that studies lakes of concentrated salt solution, known as anoxic hypersaline basins, on the floor of the Mediterranean, has discovered extremely diverse microbial communities on the surfaces of such lakes.
The anoxic basins, so called because they are devoid of oxygen, occur below 3,000 m beneath the surface and are five to ten times more saline than seawater.
Yakimov’’s team has already identified more than ten new lineages of bacteria and ancient bacteria-like organisms, which they have named the Mediterranean Sea Brine Lake Divisions.
There is ample life at the boundary between the concentrated basin and the ordinary seawater.
“Because of the very high density of the brine, it does not mix with seawater, and there is a sharp interface, about 1m thick,” explained Yakimov.
In that layer, microbial diversity is incredibly rich. (ANI)

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