DEEP SEA MINERALS - Vol 1 - Sea-Floor Massive Sulphides

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Global distribution of vent organisms

Hydrothermal vents with generally similar chemical/thermal habitats exist in all of the world’s oceans. However, there are significant differences among vent communities in different regions of the world. For example, the giant tubeworms that dominate many vent habitats in the eastern Pacific have nev- er been seen at Atlantic, Indian Ocean, or southwest Pacific vent sites. On the Mid-Atlantic Ridge, swarms of endemic vent shrimp with chemoautotrophic symbionts cover many hydro-

thermal chimneys. In the Indian Ocean, shrimp, anemones, and big, symbiont-containing snails constitute the largest portion of the biomass. Analysis of the composition of vent communities suggests at least five biogeographic provinces for vent fauna, although the number and boundaries of these provinces have yet to be resolved with any certainty (Van Do- ver et al 2002; Bachraty et al 2009; Moalic et al 2011; Rogers et al 2012).

The scaly foot snails found at vents on the Central Indian Ridge in the Indian Ocean have scales composed of iron sulphides and are the only animals known to produce metal armour. Photo courtesy of CL Van Dover.

Shrimp on theMid-Atlantic Ridge and on Indian Ocean vents (Rimi- caris sp) have lost their eyes but have evolved large light-sensing patches on their backs to “see” the chimneys they call home. They are not found in the southwest Pacific. Photo courtesy of IFREMER.

Because of the myriad of adaptations necessary to live at hydrothermal vents, most animals cannot survive there. However, the endemic vent fauna represent a source of evolutionary innovation not found elsewhere on earth. They often occur in extremely high densities at hydrothermal vents. Giant tubeworms (Riftia pachyptila) from the East Pacific Rise are among the fastest growing animals on earth. They have no mouth, gut, or anus and live their entire adult lives with one end of their bodies immersed in a hot tub and the other in ice-cold water. They are not found in the southwest Pacific. Photo courtesy of IFREMER.

THE GEOLOGY OF SEA-FLOOR MASSIVE SULPHIDES 23