sign in sign up
<<
Home , Chemosynthesis

EOSC 112 EOSC 112: hydrothermal vents Hydrothermal vents Hydrothermal vents: Discovery: first discovered in 1977 at 2500m depth at geysers on the seafloor, hot Galapagoss rift and fluid spilled out of chimneys represented an example of black smokers (iron & an alternative sulfide) supported by white smokers (barium, chemosynthetic primary calcium, silicon) production Cold seeps: similar to Distribution: mid- hydrothermal vents but seep ridges with low rates of sea floor spreading. HV are waters that are about the likely to be found at any same temperature as the number of sites of active surrounding waters volcanic activity

EOSC 112: hydrothermal vents EOSC 112: hydrothermal vents (1) Cold seawater sinks down Chimneys top some hydrothermal vents and formed from trough cracks in the crust dissolved metals that precipitate out when super-hot vent water (2) and potassium are meets nearly freezing deep ocean water removed from the seawater and grow up it becomes acidic to 9 m per (3) Calcium, sulfate and 18 months magnesium are removed from fluid (4) As water heats up, it reacts with the rocks and picks up sodium, sulfate and potassium from the surrounding crust (5) The fluids reached their highest temperatures. Copper, zink, iron, and from the crust dissolve in the fluids up to 400ºC; pH ~ 3.2; high conc. H2S; large number of cations; low or absent O2, N and P (6) Hot fluids carrying dissolved metals rise up trough the crust (7) The hydrothermal fluid mix with cold, oxygen-rich seawater. Metal and sulfur combine to form black, metal-sulfide minerals

1 EOSC 112: hydrothermal vents EOSC 112: hydrothermal vents Free energy of chemolithotrophic oxidation Chemosynthesis: fixation of inorganic carbon reactions into organic compounds using energy from Reaction Standard free chemical reaction (oxidation) rather than from energy, kJ/mol H + ½O = H O -237 sunlight () 2 2 2 2H2 + CO2 = CH4 + 2H2O-35 + - + NH4 + 1½O2 = NO2 + H2O + 2H -272 - - CO + H S + O + H O → CH O + H SO NO2 + ½O2 = NO3 -73 2 2 2 2 2 2 4 0 H2S + ½O2 = S + H2O -210 - 2- + HS + 2O2 = SO4 + H -716 0 S + 1½O2 + H2O = H2SO4 -496 The sources of energy for 2- 2- + S2O3 + 2O2 + H2O = 2SO4 + 2H -936 2+ + 3+ are reduced inorganic substances in the 2F + 2H + ½O2 = 2Fe + H2O-47 Mn2+ + H O + ½O = MnO + 2H+ -67 hydrothermal fluid 2 2 2

EOSC 112: hydrothermal vents EOSC 112: hydrothermal vents non-vent Oases on the seafloor Vent filter feeders Bacteria form the base of the trophic structure at vent vent filter scavengers communities bacteria feeders Four major trophic pathways in vent communities

vent grazers & predators • bacteria expelled in the emergent plume of a vent are dispersed deposit feeders over large distances becoming prey to not-vent filter feeders; vestimentiferans • vent filter feeders feed almost exclusively on expelled bacteria; giant clams and • vent grazers feed on the microbial mats commonly found around chimneys; Vent communities are small, ca 25-60 m in diameter. Ephemeral. • many sessile macro-invertebrates developed a symbiotic Low diverse but highly endemic communities. Out 236 described association with chemosynthetic bacteria vent species, 223 (~ 95%) are new to science

2 EOSC 112: hydrothermal vents EOSC 112: hydrothermal vents Tube worms (vestimentiferans): Riftia tube worms are Bathymodiolid Mussels: encased in leathery tubes, with only a plume of many tentacle- filter feeders, also posses a like gill filaments protruding from the open end. symbiotic bacteria, which Tube worms lack a mouth or digestive tract but still free living enables them to survive and not parasitic. They posses a special internal organ, farther from the direct , witch contain symbiotic bacteria (up to 60% of Riftia sources of vent water dry mass) Tube worms may measure 1.5 m long Vescomyid Clams: retain and 20 to 40 mm in some ability to filter-feed but diameter. Their tubes like tube worms rely heavily may be as long as 3 m on their bacterial symbionts Densities: up to 176 that live within their gills. ind.m-2 or 9 kg.m-2 Reach size of 30-40 cm

EOSC 112: hydrothermal vents EOSC 112: hydrothermal vents Vent : in densities Total of vent community of up to 1500 m-2, often can exceed 20-30 kg.m-2. Yet it is surround smoking vents and very localized and short living, feed on bacterial mats often ephemeral community. Vent community may persist from years to decades but < 100 yr

Animals developed unique adaptations: • resistance to high temperatures and large variations in salinity and oxygen; Spider crabs: • resistance to high concentrations of sulfur and other inorganic mainly scavengers substances; • grow rapidly to sexual maturity and generally gigantic; • produce many offspring; • obviously have efficient means of dispersal

3