1. Geol104/BioES154 Deep-Sea Hydrothermal Vent Communities

2. Geol 104/BioES 154 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)

3. 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

4. Geol 104/BioES 154 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. Geol 104/BioES 154 Hydrothermal Vent Communites 25 years of exploration have revealed: � 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/m 2 � 1000 x greater than typical biomass observed on deep-sea floor

6. Geol 104/BioES 154 Vestimentiferan worms (Riftia pachyptila ) Serpulid polychaete worms Hydrothermal Vent Macrofauna: Worms

7. Geol 104/BioES 154 Giant clams (Calyptogena magnifica) Mussels (Bathymodiolus thermophilus) Hydrothermal Vent Macrofauna: Bivalves

8. Geol 104/BioES 154 What supports this abundance of life around hydrothermal vents? What is the energy source for this ecosystem?

9. Geol 104/BioES 154 Chemosynthesis � Basis of life around deep sea hydrothermal vents is chemosynthesis rather than photosynthesis. Chemical energy rather than solar energy supports the ecosystem. � Chemical energy rather than solar energy supports the ecosystem. � Bacteria rather than plants are the primary producers. � Aerobic chemoautolithotrophy � CO 2 + H 2 S + O 2 + H 2 O  CH 2 O] + H 2 SO 4 � Organisms must have adaptations to prevent sulfide from poisoning oxygen binding site.

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

11. Geol 104/BioES 154 Tube Worm: Riftia pachyptila � Unusual animal � No mouth � No anus � No digestive tract � Dependent upon bacteria living in its gut or “troposome” � Gills extracts hydrogen sulfide, carbon dioxide & oxygen from seawater; blood delivers these to troposome � In return, bacteria provide nourishment for Riftia

12. Geol 104/BioES 154 Giant Clam: Calyptogena magnifica  Symbiotic bacteria in gills.  High hemoglobin content in blood. Clams on the half shell anyone?

13. 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 life- spans. � Volcanic eruptions and earthquakes pose further hazards. � These conditions favor rapid growth rates, continuous reproduction, and high fecundity.