Whatever their
origin, the bacteria that arise from vents now probably have come from a sub-seafloor microbial
biosphere.
This image shows a graphic of a vent with magma at the bottom and a black
smoker venting from the top between two ridges of basalt formed by the
preciptating metals in the vent water. In the middle, between the magma and
the ocean floor, is a rocky area where seawater seeps down through cracks in
the basalt, is heated by the magma, and rises up again. This is also depicted
as the spreading axis where the earth's tectonic plates spread apart. This same
hot, rocky area, scientists believe, is the home of microbes, shown on the
graphic by a kidney-shaped, dotted line.
They may live in such profusion in vast, warm seas under the earth's crust that, Thomas Gold of
Cornell University has theorized, were they all to emerge, they would form a blanket 1.5 meters
(5 ft.) deep over the entire land surface of our planet.
Vent bacteria grow quickly. This photo shows the growth of
floc over a formerly barren area in just one year.
This image shows the white and grey floc that looks like
a stringy plant, or kelp, against a yellow background.
Bacteria are the basis of the hydrothermal vent's food chain. Later, if the vents continue to
furnish the chemicals that the bacteria need, there will be a succession of fauna:
symbiont tube worms, clams as big as frisbees,
grazing limpets, eyeless shrimp, carnivorous crabs, and fantastic fish, such as the pink
bithitid of the Galapagos that swims head down-tail up in the mouth of vents.
This image shows small white crabs on the
rock-like ledges of a vent chimney.
No one is sure how long a vent lasts. It may be a few months, 100 years, or longer. Some vents
quit, then start again. No one knows why.
To their amazement, scientists have found that the
biomass, or number of creatures per cubic foot, and the diversity of species in an established
vent community maybe as high as the biomass and diversity of a rain forest! How could life not
just survive, but actually flourish, in an environment with no sunlight, little oxygen, high
temperatures, and a concentration of hydrogen sulfide so high that it would kill most life
on the earth's surface? Careful study of tube worms provided the answer.