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Deep-Sea Deep-Sea Hydrothermal Vent Hydrothermal Vent

CommunitiesCommunities

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Comparison with Other Comparison with Other Deep-Sea Benthic EnvironmentsDeep-Sea Benthic Environments

Most deep-sea environments are characterized by:Most deep-sea environments are characterized by:�Low availability of foodLow availability of food

No light, no photosynthesisNo light, no photosynthesisFalling remains of dead organisms, decaying organic matterFalling remains of dead organisms, decaying organic matter

�Low (0-2°C), relatively constant temperatureLow (0-2°C), relatively constant temperature�High pressure (400-500 times atmospheric)High pressure (400-500 times atmospheric)

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Summary of General Biological Summary of General Biological Characteristics of Deep-Sea MacrofaunaCharacteristics of Deep-Sea Macrofauna

�Reproduction and DevelopmentLate reproductive maturitySlow development

�PhysiologyLow metabolic rate and activity level

�EcologicalLong lived speciesSlow colonization ratesLow population densities, but high species diversity

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Hydrothermal VentsHydrothermal Vents� Vents are associated with mid-ocean ridges, spreading Vents are associated with mid-ocean ridges, spreading

centers.centers.� Cold waters percolate into crust and are geothermally Cold waters percolate into crust and are geothermally

heated before being vented at very high temperatures.heated before being vented at very high temperatures.� Vent waters are not only hot, but low in oxygen and rich Vent waters are not only hot, but low in oxygen and rich

in metals and hydrogen sulfide.in metals and hydrogen sulfide.

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Hydrothermal Vent CommunitesHydrothermal Vent Communites� 25 years of exploration have revealed:25 years of exploration have revealed:

A new phylumA new phylum At least 20 new familiesAt least 20 new families Over 90 new generaOver 90 new genera Over 300 new speciesOver 300 new species Over 250 new strains of Over 250 new strains of free-living bacteriafree-living bacteria

� BiomassBiomass Up to 30 kg/mUp to 30 kg/m22

1000 x greater than 1000 x greater than typical biomasstypical biomassobserved on observed on deep-sea floordeep-sea floor

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Vestimentiferan worms Vestimentiferan worms ((Riftia pachyptilaRiftia pachyptila ) )

Serpulid polychaete wormsSerpulid polychaete worms

Hydrothermal Vent Hydrothermal Vent Macrofauna: WormsMacrofauna: Worms

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Giant clams Giant clams ((Calyptogena magnifica)Calyptogena magnifica)

Mussels Mussels ((Bathymodiolus thermophilus)Bathymodiolus thermophilus)

Hydrothermal Vent Hydrothermal Vent Macrofauna: BivalvesMacrofauna: Bivalves

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What supports this abundance of life What supports this abundance of life around hydrothermal vents? What is around hydrothermal vents? What is the energy source for this ecosystem?the energy source for this ecosystem?

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ChemosynthesisChemosynthesis�Basis of life around deep sea hydrothermal Basis of life around deep sea hydrothermal

vents is vents is chemosynthesischemosynthesis rather than rather than photosynthesis.photosynthesis. Chemical energy rather than solar energy Chemical energy rather than solar energy

supports the ecosystem.supports the ecosystem. Bacteria rather than plants are the primary Bacteria rather than plants are the primary

producers.producers.

�Aerobic Aerobic chemoautolithotrophychemoautolithotrophy COCO22 + H + H22S + OS + O22 + H + H22O O CHCH22O] + HO] + H22SOSO44

Organisms must have adaptations to preventOrganisms must have adaptations to prevent

sulfide from poisoning oxygen binding site.sulfide from poisoning oxygen binding site.

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Vent Ecosystems Depend on Vent Ecosystems Depend on 2 Types of Bacteria:2 Types of Bacteria:

Free-living bacteriaFree-living bacteria Symbiotic bacteriaSymbiotic bacteria

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Tube Worm: Tube Worm: Riftia pachyptilaRiftia pachyptila

� Unusual animalUnusual animal No mouthNo mouth No anusNo anus No digestive tractNo digestive tract Dependent upon bacteria Dependent upon bacteria

living in its gut or living in its gut or ““troposometroposome””

Gills extracts hydrogen Gills extracts hydrogen sulfide, carbon dioxide & sulfide, carbon dioxide & oxygen from seawater; oxygen from seawater; blood delivers these to blood delivers these to troposometroposome

In return, bacteria provide In return, bacteria provide nourishment for nourishment for RiftiaRiftia

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Giant Clam: Giant Clam: Calyptogena magnificaCalyptogena magnifica

Symbiotic bacteria in gills.Symbiotic bacteria in gills. High hemoglobin content High hemoglobin content

in blood.in blood.

Clams on the half shell anyone?Clams on the half shell anyone?

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Hydrothermal Vent Macrofauna: Hydrothermal Vent Macrofauna: Environmental Constraints on Life Cycles Environmental Constraints on Life Cycles

and Reproductionand Reproduction

� Suitable vent environments for these Suitable vent environments for these organisms are rare.organisms are rare.

� Individual vents have short life-Individual vents have short life-spans.spans.

� Volcanic eruptions and earthquakes Volcanic eruptions and earthquakes pose further hazards.pose further hazards.

�These conditions favor rapid growth These conditions favor rapid growth rates, continuous reproduction, and rates, continuous reproduction, and high fecundity.high fecundity.