Hypersaline anoxic basins
Recently, van der Wielen et al.
(2005) discovered remarkable prokaryotic faunas in the deep hypersaline
anoxic
basins of the Mediterranean Sea. Contrary to popular belief that these basins
represent biological dead ends, van der Wielen et al. (2005) found
endemic prokaryotic
faunas in four basins, L’Atalante, Bannock, Discovery, and Urania. The brines in these basin are under high
pressure, anoxic conditions and saturated in salt.
van Wielen et al. (2005) new discoveries of life include a deeply
branching order within the Euryarchaeota.
Additionally, the Discovery basin, indicates that life can
flourish in
nearly saturated MgCl5.
Where are hypersaline
anoxic basins typically found?
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Hypersaline anoxic basins
occur
mainly in the Mediterranean Sea (van der Wielen 2005). Each basin is geochemically unique and
isolated because the high densities of the hypersaline brines limit
mixing and
the bathometery of the Mediterranean
prevents
‘spilling over.’ Some living
bacteria have been found in sapropels buried under sediment (Parkes et
al. 2000). Other potential
hypersaline anoxic basins are found in the Dead Sea and Lake Bonney
in the Antarctic (der Wielen et al. 2005).
Each
basin
was at a different depth, L’Atalante
(30-60 m),
Bannock (300-500 m), Discovery (10-60 m), and Urania (80-200). The differences in depth suggest that the
depth does not control the distribution of the prokaryotes, but the
high
salinity of the water (van der Wielen 2005).
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| Distribution of hypersaline basins that are known to contain
life. |