Travel Reference
In-Depth Information
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Inoceramids
and
Isotopes
Whereas the ocean floor at this depth [2500 meters] tends to be
rather poor in organisms large enough to be seen from the
ALVIN, the spring [a hot, volcanic water seep] seemed to be a
veritable garden or aquarium full of large life forms. White clams,
mussels, large white crabs resembling those of coastal tide pools,
wotms with featherdusters living in calcareous tubes were every-
where. The number of animals, the total amount or biomass,
seemed far, far larger than anything ever seen on the deep sea
floor. Moreover, most of the animals did not resemble the deep
sea kind sea cucumbers, anemones, shrimp—at all, but rather
reminded me of the fauna of a coastal tide pool. On the first dive
I was especially struck by the white clams with enormous shells
measuring up to 20 cm in length; we later found them to weigh
several pounds each. (Van Andel, 1977, pp. 149-150)
All of this newly discovered "vent fauna" lived well below the zone of
plankton, just like the inoceramids of the Cretaceous. The vent fauna, and
faunas discovered soon after in regions of cold methane seeps (areas where
cold, methane-rich water comes up through the sea floor), used an entirely
different energy source than sunlight for the base of their food chains. They
used methane gas.
The discovery of deep-sea vent faunas revolutionized not only biologi-
cal oceanography but in a significant way paleontology as well. Hydrother-
mal vent and cold seep-faunas (where animals cluster around natural gas,
cold brine, or petroleum seeps) are diverse and rich in life in places where life
is normally sparse and rare.
The discovery of hydrothermal vent communities in the late 1970s
alerted biologists to the presence of significant associations of "chemoau-
totrophic" organisms on the sea floor—organisms that use as their primary
energy source not sunlight but other types of energy. By the 1980s it was re-
alized that two distinct associations of animals are present: hydrothermal
vent faunas and "cold-seep" faunas. Cold seeps are found in a variety of vol-
canic areas and over organic-rich sediment accumulations. Cold seeps produce
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