1. Deep-Sea Hydrothermal Vent Communities

2. 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 ( times atmospheric)

3. 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
Low population densities, but high species diversity

4. Hydrothermal Vents
Vents are associated with mid-ocean ridges, spreading
centers.
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.

5. Black and White Smokers
2. The seawater continues to seep far below this point in the ocean crust. Energy radiating up from molten rock deep beneath the ocean floor raises the water's temperature to around °C. As the water heats up, it reacts with the rocks in the ocean crust. These chemical reactions change the water in the following way: All oxygen is removed. It becomes acidic. It picks up dissolved metals, including iron, copper and zinc. It picks up hydrogen sulfide.
3. Hot liquids are less dense and therefore more buoyant than cold liquids. So the hot hydrothermal fluids rise up through the ocean crust just as a hot-air balloon rises into the air. The fluids carry the dissolved metals and hydrogen sulfide with them.
4. The hydrothermal fluids exit the chimney and mix with the cold seawater. The metals carried up in the fluids combine with sulfur to form black minerals called metal sulfides. These tiny mineral particles give the hydrothermal fluid the appearance of smoke. Many factors trigger this reaction. One factor is the cold temperature of the seawater. A second equally important factor is the presence of oxygen in the seawater. Without oxygen, the minerals would never form. In white smokers, the hydrothermal fluids mix with seawater under the seafloor. Therefore, the black minerals form beneath the seafloor before the fluid exits the chimney. Other types of compounds, including silica, remain in the fluid. When the fluid exits the chimney, the silica precipitates out. Another chemical reaction creates a white mineral called anhydrite. Both of these minerals turn the fluids that exit the chimney white
Black and White Smokers

8. Hydrothermal Vent Distribution

9. 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

10. Vestimentiferan worms (Riftia pachyptila )
Hydrothermal Vent
Macrofauna: Worms
Vestimentiferan worms (Riftia pachyptila )
Serpulid polychaete worms

11. Giant clams (Calyptogena magnifica)
Hydrothermal Vent
Macrofauna: Bivalves
Giant clams (Calyptogena magnifica)
Mussels
(Bathymodiolus thermophilus)

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

13. Chemosynthesis
Basis of life around deep sea hydrothermal vents is chemosynthesis rather than photosynthesis.
Chemical energy rather than solar energy supports the ecosystem.
Bacteria rather than plants are the primary producers.

14. Vent Ecosystems Depend on 2 Types of Bacteria:
Free-living bacteria
Symbiotic bacteria
Geol 104/BioES 154

15. Tube Worm: Riftia pachyptila
Unusual animal
No mouth
No anus
No digestive tract
Dependent upon bacteria living in its gut
Gills extracts hydrogen sulfide, carbon dioxide & oxygen from seawater; blood delivers these to gut
In return, bacteria provide nourishment for it

16. Hydrothermal Vent Macrofauna: Environmental Constraints on Life Cycles and Reproduction
Suitable vent environments for these organisms are rare.
Individual vents have short life-spans.
Volcanic eruptions and earthquakes pose further hazards.
These conditions favor rapid growth rates, continuous reproduction.

17. Geol 104/BioES 154

18. Geol 104/BioES 154

19. Geol 104/BioES 154

20. Geol 104/BioES 154

21. Geol 104/BioES 154