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Hydrothermal Vent Communities
Comparison with Other
Deep-Sea Benthic Environments
Most deep-sea environments are characterized by:
�Low availability of food
No light, no photosynthesis
Falling remains of dead organisms, decaying organic matter
�Low (0-2°C), relatively constant temperature
�High pressure (400-500 times atmospheric)
Geol 104/BioES 154
Summary of General Biological Characteristics
of Deep-Sea Macrofauna
� Reproduction and Development
Late reproductive maturity
Slow development
� Physiology
Low metabolic rate and activity level
� Ecological
Long lived species
Slow colonization rates
Low population densities, but high species diversity
Geol 104/BioES 154
Hydrothermal Vents
� Vents are associated with mid-ocean ridges, spreading
� Cold waters percolate into crust and are geothermally
heated before being vented at very high temperatures.
� Vent waters are not only hot, but low in oxygen and rich
in metals and hydrogen sulfide.
Geol 104/BioES 154
Hydrothermal Vent Communites
� 25 years of exploration have revealed:
A new phylum
At least 20 new families
Over 90 new genera
Over 300 new species
Over 250 new strains of
free-living bacteria
� Biomass
Up to 30 kg/m2
1000 x greater than
typical biomass
observed on
deep-sea floor
Geol 104/BioES 154
Hydrothermal Vent
Macrofauna: Worms
Vestimentiferan worms
(Riftia pachyptila )
Geol 104/BioES 154
Serpulid polychaete worms
Hydrothermal Vent
Macrofauna: Bivalves
Giant clams
(Calyptogena magnifica)
Geol 104/BioES 154
(Bathymodiolus thermophilus)
What supports this abundance of life around
hydrothermal vents? What is the energy
source for this ecosystem?
Geol 104/BioES 154
�Basis of life around deep sea hydrothermal
vents is chemosynthesis rather than
 Chemical energy rather than solar energy
supports the ecosystem.
 Bacteria rather than plants are the primary
�Aerobic chemoautolithotrophy
 CO2 + H2S + O2 + H2O  CH2O] + H2SO4
 Organisms must have adaptations to prevent
sulfide from poisoning oxygen binding site.
Geol 104/BioES 154
Vent Ecosystems Depend on
2 Types of Bacteria:
Free-living bacteria
Geol 104/BioES 154
Symbiotic bacteria
Tube Worm:
Riftia pachyptila
� Unusual animal
 No mouth
 No anus
 No digestive tract
 Dependent upon bacteria
living in its gut or
 Gills extracts hydrogen
sulfide, carbon dioxide &
oxygen from seawater;
blood delivers these to
 In return, bacteria
provide nourishment for
Geol 104/BioES 154
Giant Clam:
Calyptogena magnifica
 Symbiotic bacteria in gills.
 High hemoglobin content
in blood.
Clams on the half shell anyone?
Geol 104/BioES 154
Hydrothermal Vent Macrofauna: Environmental
Constraints on Life Cycles and Reproduction
� Suitable vent environments for these
organisms are rare.
� Individual vents have short lifespans.
� Volcanic eruptions and earthquakes
pose further hazards.
�These conditions favor rapid growth
rates, continuous reproduction, and
high fecundity.
Geol 104/BioES 154