L'Atalante basin is a
hypersaline brine lake
A hypersaline lake is a landlocked body of water that contains significant concentrations of sodium chloride, brines, and other salts, with saline levels surpassing that of ocean water (3.5%, i.e. ).
Specific microbial species can thrive in h ...
at the bottom of the
Mediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the ea ...
about west of the island of
Crete
Crete ( el, Κρήτη, translit=, Modern: , Ancient: ) is the largest and most populous of the Greek islands, the 88th largest island in the world and the fifth largest island in the Mediterranean Sea, after Sicily, Sardinia, Cyprus, and ...
.
It is named for the French ''L'Atalante'',
one of the
oceanographic research vessel
A research vessel (RV or R/V) is a ship or boat designed, modified, or equipped to carry out research at sea. Research vessels carry out a number of roles. Some of these roles can be combined into a single vessel but others require a dedicated ...
s involved in its discovery in 1993.
L'Atalante and its neighbors the Urania and Discovery deep hyper saline
anoxic basins
Anoxic waters are areas of sea water, fresh water, or groundwater that are depleted of dissolved oxygen. The US Geological Survey defines anoxic groundwater as those with dissolved oxygen concentration of less than 0.5 milligrams per litre. Anox ...
(DHABs) are at most 35,000 years old. They were formed by
Messinian evaporite
The Messinian evaporite deposit is a geological deposit of evaporites which was found on Sicily and named after the city of Messina. It was later found to underlie much of the bed of the Mediterranean Sea, including the L'Atalante basin. It was f ...
salt deposits dissolving out of the
Mediterranean Ridge
The Mediterranean Ridge is a wide ridge in the bed of the Mediterranean Sea, running along a rough quarter circle from Calabria, south of Crete, to the southwest corner of Turkey.
It is an accretionary wedge caused by the African Plate subductin ...
and collecting in
abyssal
The abyssal zone or abyssopelagic zone is a layer of the pelagic zone of the ocean. "Abyss" derives from the Greek word , meaning bottomless. At depths of , this zone remains in perpetual darkness. It covers 83% of the total area of the ocean an ...
depressions about deep.
L'Atalante is the smallest of the three; its surface begins at about below sea level.
Description and biology
The L'Atalante basin's salinity is near saturation at 365 (about 8 times that of ordinary seawater), which prevents it from mixing with the oxygenated waters above; therefore, it is completely anoxic.
[ The approximately ]halocline
In oceanography, a halocline (from Greek ''hals'', ''halos'' 'salt' and ''klinein'' 'to slope') is a Cline (hydrology), cline, a subtype of chemocline caused by a strong, vertical salinity gradient within a body of water. Because salinity (in c ...
between the seawater above and brine
Brine is a high-concentration solution of salt (NaCl) in water (H2O). In diverse contexts, ''brine'' may refer to the salt solutions ranging from about 3.5% (a typical concentration of seawater, on the lower end of that of solutions used for br ...
below teems with bacterial and archaea
Archaea ( ; singular archaeon ) is a domain of single-celled organisms. These microorganisms lack cell nuclei and are therefore prokaryotes. Archaea were initially classified as bacteria, receiving the name archaebacteria (in the Archaebac ...
l cells: they are chemoautotroph
A Chemotroph is an organism that obtains energy by the oxidation of electron donors in their environments. These molecules can be organic (chemoorganotrophs) or inorganic (chemolithotrophs). The chemotroph designation is in contrast to phototrop ...
s, which feed on ammonia
Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous was ...
from the brine but cannot function without some oxygen. Members of archaeal anaerobic methane oxidizers group 1 (ANME-1) and haloarchaea are found only in the halocline zone. No group of organisms manages to prosper in all three zones.[ In the brine, there are fewer cells; ]extremophile
An extremophile (from Latin ' meaning "extreme" and Greek ' () meaning "love") is an organism that is able to live (or in some cases thrive) in extreme environments, i.e. environments that make survival challenging such as due to extreme temper ...
s predominate, including members of the deep-sea hydrothermal vent
A hydrothermal vent is a fissure on the seabed from which geothermally heated water discharges. They are commonly found near volcanically active places, areas where tectonic plates are moving apart at mid-ocean ridges, ocean basins, and hotspot ...
euryarchaeota (DHVEs), ''Methanohalophilus
In taxonomy, ''Methanohalophilus'' is a genus of the Methanosarcinaceae.See the NCBIbr>webpage on Methanohalophilus Data extracted from the
The species are strictly anaerobic and live solely through the production of methane, using methyl co ...
'' and ''Pseudomonadota
Pseudomonadota (synonym Proteobacteria) is a major phylum of Gram-negative bacteria. The renaming of phyla in 2021 remains controversial among microbiologists, many of whom continue to use the earlier names of long standing in the literature. The ...
'' (formerly ''Proteobacteria'').[ ]Eukaryote
Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacte ...
s are also found in l'Atalante, including ciliates (45%), dinoflagellates
The dinoflagellates (Greek δῖνος ''dinos'' "whirling" and Latin ''flagellum'' "whip, scourge") are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered algae. Dinoflagellates are ...
(21%) and choanoflagellates (10%).Microbe
A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...
s found in the sediments are almost all (90%) various species of '' Bacillus''.[ In 2010, three metazoan species, all in the ]Loricifera
Loricifera (from Latin, '' lorica'', corselet (armour) + ''ferre'', to bear) is a phylum of very small to microscopic marine cycloneuralian sediment-dwelling animals that had been determined to be 37 described species, in 9 genera, bu ...
phylum, were discovered living in the sediment, the first multicellular lifeforms known to live entirely without oxygen.
References
External links
* Stephen Ornes
Animals without oxygen, underwater
ScienceNews for Students, 27 Apr 2010
{{portalbar, Oceans
Anoxic waters
Oceanic basins of the Atlantic Ocean
Mediterranean Sea