7. Deep Sea Reducing Habitats. Deep-Sea Reducing Habitats

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1 7. Deep Sea Reducing Habitats History of Deep Sea Exploration Discovery of hydrothermal vents Hydrothermal Vents Living in reducing environments Chemosynthesis Life history strategies Other Reducing Habitats Cold Seeps Whale Falls Dr Rhian G. Waller 21st April 2010 Reading: Van Dover et al., 2002, Science 295: Deep-Sea Reducing Habitats Habitat where energy from reduced inorganic chemical species (e.g. H 2 S, H 2, CH 4 ) is converted, through microbial endosymbiosis, into biomass of higher organisms Whole communities driven by chemosynthesis Whole ecosystem micro macro fauna living off chemosynthesis Oasis of diversity on deep-sea floor General deep-sea is sediments - ~1g/m 2 biomass Reducing Habitats - >10kg/m 2 biomass 1

2 Deep Sea Exploration Forbes Azoic Hypothesis 1844 The deep ocean (below 550m) is lifeless Too cold, too much pressure, no light Caused controversy James Clark Ross Micheal Sars Wyville Thomson & William Carpenter HMS Lightening & HMS Porcupine Life to 1000m HMS Challenger Expedition ,000 nautical miles 492 deep soundings; 133 bottom dredges; 151 pelagic trawls How do species live in the deepsea? Discovered 4700 new species Discovered food fall Laid the foundation of oceanographic research 2

3 1% of Deep Sea Explored We know more about the surface of the moon than the bottom of our oceans Majority of the world is deep-sea USS San Francisco 2005 Uncharted seamount 200m depth Hydrothermal Vent Discovery 1977 Geology Cruise to Galapagos Rift 3

4 Hydrothermal Vent Discovery 1977 Geology Cruise to Galapagos Rift Lonsdale, 1977 Hydrothermal Vent Discovery 1977 Geology Cruise to Galapagos Rift Lonsdale,

5 Hydrothermal Vent Discovery 1979 Biologists go to Galapagos Vents DSV Alvin & Lulu Found abundant life Fissures and conduits Hydrothermal Vents Allow water to get close to, heated by magma Tectonic plates Hotspots Water is superheated and escapes back to seafloor Picks up minerals from rock Up to ~400 C Pressure & salinity increase boiling point Can form chimneys 5

6 Hydrothermal Vents Superheated water hits cold water Precipitation of minerals Anhydrite Sulphides Copper, Iron, Zinc Black Smoker Hot water High sulphides White Smoker Cooler water Barium, calcium, silicon Hydrothermal Vents Black Smoker ~ >300 C White Smoker <300 C 6

7 Global Hydrothermal Vents Vents are volatile & ephemeral Clogged conduits Sulphide build up Tectonic shifts Expanded conduits Longevity of Vents Tunnicliffe,

8 Estimated by: Heat loss in rocks (Macdonald et al., 1980) Sulphide Radiochronology (Stakes & Moore, 1989; Lalou et al., 1984) Clam ages (Lutz et al, 1988; Fisher et al., 1988) decades years 4-40 years Living in Reducing Habitats Extremophiles Organisms that live and thrive in geochemically extreme conditions Conditions that would usually be detrimental Hyperthermophiles Live in temps greater than 80 C Enzymes that function at higher temps Chemosynthesis Primary production without using sunlight 8

9 Living in Reducing Habitats 6 Carbon dioxide (CO 2 ) + 6 Oxygen (O 2 ) + 24 Hydrogen sulfide (H 2 S) Glucose (C 6 H 12 O 6 ) + 24 sulfur (S) + 18 Water (H 2 O) Chemosynthesis Only bacteria can do this Endosymbionts Endosymbiosis Evolved endosymbiosis with chemosynthetic bacteria Riftia Trophosome Clams/mussels Gills 9

10 Living in Reducing Habitats Very high growth rates Grow to reproductive size fast Van Dover, 2000 Other Reducing Habitats Cold Seeps Cold water carrying hydrocarbons, methane and hydrogen sulphate Whale Falls Break down of lipids by bacteria creates sulphates 10

11 First discovered in 1984 Cold Seeps Gulf of Mexico, 3000m depth Often form brine pools Salinity 3-5 times greater than normal Salt leached from rocks High quantities of hydrogen sulphide, methane & hydrocarbons Emit at a slower, more dependable rate than hydrothermal vents Longer lived organisms s on years Brine Pools Methane bubbles seabed Sediment Gas reservoir Bathymodiolus childressi Salt diapir 11

12 Cold Seeps Mostly along continental margins Gases and oils seep from sediments Brine pools can form in other areas of high salt Antarctica Salt excluded from sea ice formation Carbonate formation Precipitation from seep waters as byproduct of microbial metabolism Whale Falls Whale carcass that has fallen to the seafloor Shallow water Scavengers quickly take over Carcass devoured in months Deep water Fewer scavengers Body lasts longer (10s of years) Specialized ecosystem 12

13 Whale Falls Three stages of decomposition Mobile Scavengers Hagfish, sleeper sharks consume flesh Enrichment Opportunistic Smaller organisms move in and feed Sulfophilic Bacteria (anaerobic) break down lipids in bones Whale Falls Sulphate reducing bacteria Use dissolved sulphate in water for chemosynthesis Excrete hydrogen sulphide Support chemosynthetic bacteria communities Smith and Baco,

14 Hydrothermal vent endemic Whale endemic > Deep Sea 30 ~10 6 to 10 7 Food Webs Are organisms at reducing environments that use both forms of primary production Van Dover,

15 Conclusions Chemosynthetically driven communities and ecosystems Hydrothermal Vents Hot water, sulphides Cold Seeps Cold water, hydrocarbons, sulphides Whale Falls Cold water, lipids Faunal adaptations Thermophiles Chemosynthesis endosymbiosis Faster growth rates 15