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Hydrothermal Vents
"oases of life."
Evolution
Physiology
Biodiversity
Barbara Zimmermann , Kirstin Claußen , Ulrich Markmann
Hydrothermal vents are
geysers on the seafloor.
They continuously spew
super-hot, mineral-rich water
which sustains a diverse
community of organisms.
1977:
First discovery of a deep sea life
community around a hot spring on
the Galapagos volcanic rift
(Ecuador)
Where can the smokers be found?
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Vents form along mid-ocean ridges
Also found near underwater volcanos
Hydrothermal systems consist of
circulation zones where seawater
interacts with rock changing
chemical and physical characteristics
of both the seawater and the rock.
The altered seawater, which is
injected back into the ocean at
hydrothermal vents, is called
hydrothermal fluid. Because of
different conditions in the seawater
the dissolved minerals precipitate
and form hydrothermal plumes.
Hydrothermal fluid:
• Temperature: 350 - 450°C
• Anoxic
• Acidic
• reduced metals: Fe, Mn, Zn, Cu, Ag, Cd, …
• gases: H2S, NH3, CH4, H2, CO2, …
• large amounts of reduced sulfur compounds
Hydrothermal plume:
Hot vents = “Black smokers”
• temperature of hydrothermal fluid: 270 – 280 °C
• particles: sulfides (pyrrhotite FeS, sphalerite ZnS, chalcopyrite CuFeS2, etc.)
sulfates (anhydrite CaSO4, barite BaSO4)
• flow rate:
1-2 m/sec
Warm vents = “White smokers”
• temperature of hydrothermal fluid: 6 – 23 °C
• particles:
barium, calcium, silicon compounds
• flow rate:
0.5 -2 cm/sec
„At deep sea vents all animals and surfaces are
coated with films and mats of microbial
communities“
Conditions:
Extreme temperatures
High pressure
Absence of light
Primary production in the absence of light
What serves as energy source?
Hypotheses about the actual source of primary organic carbon
Most credible: chemoautotrophic theory
¾Primary organic carbon production via chemoautrotophs
-carbon source: CO2
-electron donors: H2S, H2, CH4 etc.
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organic thermogenesis hypothesis
¾ abiotic process in earth‘s crust:
-High thermal energy, ionization radiation
-precursors: CO2, N2, NH3, H2, CH4…
¾CO2 is converted into simple sugars
¾Chemoheterotrophs: Carbon → biomass
advective plume hypothesis
¾ settling of organic carbon from near the ocean surface and concentration
around hydrothermal vents by advection (uprising water column due to heat)
-advection draws water and DOM in from relatively great distances
¾ primary production: heterotrophs, photoautotrophy
- hydrothermal vent communities provide organic carbon to macrofauna 3 major mechanisms to transfer organic carbon and energy to macrofauna:
- endosymbiotic relationship between vent bacteria and an invertebrate
(e.g., tube worm)
- ‘microbial gardening’: bacteria grow on specialised appendages of
mussels and other invertebrates, e.g., tentacles and gills, invertebrates
consume bacteria, retain a small number of bacteria
- direct consumption of free-living bacteria, filaments or mats by crabs,
amphipods, predatory fish and even other microorganisms (certain bacteria)
Invertebrates at hydrothermal vents
• tube worms over 2m in length, Riftia pachyptila
• Pompeii worm, Alvinella
• giant clams, mussels
• sea anemones
• snakelike fish with bulging eyes
• miniature lobsters called galatheids
• Crabs, shrimps, amphipods
• octopuses
... and more ...
Chemolithotrophic prokaryotes at hydrothermal vents
presumably determining primary production
Prokaryotes
e- donor
e- acceptor
Product from donor
Sulfur-oxidizing
HS-, S0, S2O32-
O2, NO3-
S0, SO4-
Nitrifying
NH4+, NO2-
O2
NO2-, NO3-
Sulfate-reducing
H2
S0, SO42-
H2S
Methanogenic
H2
CO2
CH4
Hydrogen-oxidizing
H2
O2, NO3-
H2O
Iron and manganeseoxidizing
Fe2+, Mn2+
O2
Fe3+, Mn4+
Methylotrophic
CH4 , CO
O2
CO2
on
b
r
Ca
:C
e
c
r
sou
Many chemolitoautotrophs are able to use several different e--acceptors
in conjunction with H2
→ advantage for life in fluctuating geochemical environment
O2
A deep-sea symbiosis:
the giant worm Riftia pachyptila
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Up to 3m in lenght
Found in depth
>2500m
Devoid of a digestive
tract
Symbiotic with the
primary producers of
the deep-sea: sulfuroxidizing bacteria
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Trophosome contains
the symbiotic bacteria
Bacteria can make up
about 15% of the
worm´s body weight
The bacteria grow on
the substances
provided by the
worm and synthesize
the organic molecules
the worm needs and
they grow fast
S-Sulfohemoglobin
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Special high molecular hemoglobins
Floats freely in the blood
Can bind both oxygen and hydrogen sulfide
Exploretheabyss.com
The symbiont
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Found free-living and symbiotic form
As biofilms or mats around the vent sites
Perspectives
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Medical applications of enzymes and other
specialized molecules
Possible existence of similar environments in
other worlds?