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 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? 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 Primary organic carbon production via chemoautrotophs -carbon source: CO 2 -electron donors: H 2 S, H 2, CH 4 etc. all theories might contribute each to the primary production in hydrothermal vent communities organic thermogenesis hypothesis abiotic process in earth s crust: -High thermal energy, ionization radiation -precursors: CO 2, N 2, NH 3, H 2, CH 4 CO 2 is converted into simple sugars Chemoheterotrophs: Carbon biomass advective plume hypothesis 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 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 Sulfur-oxidizing Nitrifying e - donor e - acceptor HS -, S 0, S 2 O 2-3 O 2, NO - 3 S 0, SO - 4 Product from donor NH + 4, NO - 2 O 2 NO - 2, NO - 3 Sulfate-reducing H 2 S 0, SO 2-4 H 2 S Methanogenic H 2 CO 2 CH 4 Hydrogen-oxidizing oxidizing H 2 O 2, NO - 3 H 2 O Iron and manganese- oxidizing Methylotrophic Fe 2+ Fe 2+, Mn 2+ O 2 Fe 3+, Mn 4+ CH 4, CO O 2 CO 2 Many chemolitoautotrophs are able to use several different e - -acceptors in conjunction with H 2 advantage for life in fluctuating geochemical environment Carbon source: CO 2
A deep-sea symbiosis: the giant worm Riftia pachyptila Up to 3m in lenght Found in depth >2500m Devoid of a digestive tract Symbiotic with the primary producers of the deep-sea: sulfur- oxidizing bacteria
Trophosome contains the symbiotic bacteria Bacteria can make up about 15% of the worm s 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-SulfohemoglobinSulfohemoglobin Special high molecular hemoglobins Floats freely in the blood Can bind both oxygen and hydrogen sulfide Exploretheabyss.com
The symbiont Found free-living and symbiotic form As biofilms or mats around the vent sites
Perspectives Medical applications of enzymes and other specialized molecules Possible existence of similar environments in other worlds?