Hydrothermal Hydrothermal VentsVents""oasesoases of life." of life."

EvolutionEvolutionPhysiologyPhysiologyBiodiversityBiodiversity

Barbara Zimmermann , Kirstin Claußen , Ulrich Markmann

HydrothermalHydrothermal ventsvents arearegeysersgeysers on the seafloor. on the seafloor.

TheyThey continuously continuously spewspewsupersuper--hot, mineralhot, mineral--rich water rich water

which sustains awhich sustains a diverse diverse community of organisms.community of organisms.

1977:First discovery of a deep sea life community around a hot spring onthe 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 pressureAbsence 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 theoryPrimary organic carbon production via chemoautrotophs

-carbon source: CO2-electron donors: H2S, H2, CH4 etc.

all theories might

contribute each to the

primary production in

hydrothermal vent

communities

organic thermogenesis hypothesisabiotic process in earth‘s crust:

-High thermal energy, ionization radiation-precursors: CO2, N2, NH3, H2, CH4…

CO2 is converted into simple sugarsChemoheterotrophs: Carbon → biomass

advective plume hypothesissettling 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

ProkaryotesProkaryotes ee-- donordonor ee-- acceptoracceptor Product from donorProduct from donor

SulfurSulfur--oxidizingoxidizing HSHS--, S, S00, S, S22OO3322-- OO22, NO, NO33

-- SS00, SO, SO44--

NitrifyingNitrifying NHNH44++, NO, NO22

-- OO22 NONO22--, NO, NO33

--

SulfateSulfate--reducingreducing HH22 SS00, SO, SO4422-- HH22SS

MethanogenicMethanogenic HH22 COCO22 CHCH44

HydrogenHydrogen--oxidizingoxidizing HH22 OO22, NO, NO33-- HH22OO

Iron and manganeseIron and manganese--oxidizingoxidizing

FeFe2+2+, Mn, Mn2+2+ OO22 FeFe3+3+, Mn, Mn4+4+

MethylotrophicMethylotrophic CHCH4 4 , CO, CO OO22 COCO22

Carbon source: CO2

Many chemolitoautotrophs are able to use several different e--acceptors in conjunction with H2

→ advantage for life in fluctuating geochemical environment

A deepA deep--sea symbiosis:sea symbiosis:the giant worm the giant worm Riftia pachyptilaRiftia pachyptila

Up to 3m in lenghtUp to 3m in lenght

Found in depth Found in depth >2500m>2500m

Devoid of a digestive Devoid of a digestive tracttract

Symbiotic with the Symbiotic with the primary producers of primary producers of the deepthe deep--sea: sulfursea: sulfur--oxidizing bacteriaoxidizing bacteria

Trophosome contains Trophosome contains the symbiotic bacteriathe symbiotic bacteriaBacteria can make up Bacteria can make up about 15% of the about 15% of the wormworm´́s body weights body weightThe bacteria grow on The bacteria grow on the substances the substances provided by the provided by the worm and synthesize worm and synthesize the organic molecules the organic molecules the worm needs and the worm needs and they grow fastthey grow fast

SS--SulfohemoglobinSulfohemoglobin

Special high molecular hemoglobinsSpecial high molecular hemoglobinsFloats freely in the blood Floats freely in the blood Can bind both oxygen Can bind both oxygen andand hydrogen sulfidehydrogen sulfide

Exploretheabyss.com

The symbiontThe symbiont

Found freeFound free--living and symbiotic formliving and symbiotic formAs biofilms or mats around the vent sitesAs biofilms or mats around the vent sites

PerspectivesPerspectives

Medical applications of enzymes and other Medical applications of enzymes and other specialized moleculesspecialized moleculesPossible existence of similar environments in Possible existence of similar environments in other worlds?other worlds?