Ocean and Deep Sea Terms

(the study of the deep seas or oceans involves the abyss or the "deep seas" which cover almost two-thirds of the earth's surface; showing applicable scientific terminology in this unit)

The most recent geological era, extending from 65 million year ago, when the dinosaurs became extinct, to the present.

It is sometimes referred to as the "Age of Mammals"; its literal meaning comes from Greek, "recent life".

The process of carbon fixation carried out by certain microbes, based on the energy in certain reduced compounds; such as, methane or hydrogen sulfide, as opposed to the use of light energy, as in photosynthesis.

The discovery of chemosynthesis in the deep ocean was possibly the most striking scientific discovery in the field of oceanography during the twentieth century, so much so that scientists now think in terms of "before 1977" and "after 1977."

The ecosystems of the hydrothermal vents depend less on the sun's energy than any of the other systems on the earth.

chlorinated hydrocarbons, CHCs
Hydrocarbons are compounds composed of carbon and hydrogen.

When they are chlorinated, chlorine is substituted for one or more of the hydrogens. Low molecular weight chlorinated hydrocarbons; such as, carbon tetrachloride, are highly volatile and relatively unstable in the environment.

climax community
A biological community at equilibrium.
cold seeps, cold vents
Areas of the ocean floor where hydrogen sulfide, methane and other hydrocarbon-rich fluid seepage occur.
Species belonging to the same genus.
An order of small crustaceans on the order of a millimeter (.039 inches) in length.

They are a diverse group, with benthic and parasitic forms, but the pelagic copepods typically dominate the mesozooplankton.

In biogeography, this refers to species that have a global distribution.
curie, Ci
1. The basic unit of radioactivity.

Named after Marie Curie, it is equal to the radioactivity emitted by a gram of radium, or 37 billion disintegrations per second. The Three Mile Island nuclear accident released about 50 curies.

2. A former unit of radioactivity, equal to 3.7 x 1010 becquerels (radioactive disintegrations).

One gram of radium has a radioactivity of about one curie.

deep scattering layers
The layers observed through the water column (vertical section of the sea) on echo sounders.

Echo sounders are measuring instruments that send out acoustic pulses in water and measure distances in terms of the time for the echo of the pulse to return.

SONAR is an acronym for "sound navigation ranging"; ASDIC is an acronym for "antisubmarine detection investigation committee".

The name refers to the way they scatter sound waves. The layers are typically composed of krill, midwater fish, and siphonophores (species which form complex free-swimming communities composed of numerous zooids of various kinds, or organic bodies or cells having locomotion, some of which act as floats or as swimming organs, others as feeding or nutritive zooids, and others as reproductive zooids).

Deep Sea Numerical Statistics
1. Average weight of organisms per square meter (3.28 feet) near the surface: five kilograms (eleven pounds).

By comparison, the biomass at great depths is less than one gram per square meter (3.28 feet); there, the populations are less dense, although the diversity of species is greater.

2. Rate of expansion between tectonic plates under the Arctic Ocean: seven millimeters (.28 inches) a year.

Compare this to the rate in the Pacific, where they separate at a speed of 18 centimeters (7 inches) per year; which is about twenty-five times faster.

3. Average depth of the oceans: 3,729 meters (12,234 feet or 2.32 miles).
4. Average depth of the Pacific, the deepest and largest of all oceans: 4,188 meters (13,740 feet or 2.60 miles).

By itself, it represents nearly half of the expanse of water on earth.

5. Hydrothermal sites discovered in the last 25 years: 100.
—Compiled from and based on information located in
The Deep, The Extraordinary Creatures of the Abyss by Claire Nouvian;
The University of Chicago Press; Chicago, Illinois; 2007; page 246.
diurnal tide
A tide with one high water and one low water in a tidal day of approximately 24 hours.
1. A marine microorganism having a calcareous shell with openings where pseudopods protrude.
2. A living organism, often microscopic, surrounded by a calcareous or siliceous envelope.

Foraminifers are abundant in sedimentary layers and provide information on the origin and evaluation of the deep substratum.

hydrocarbon seeps
Areas where hydrocarbons seep slowly from the sea floor, and which may be associated with specific faunal compositions.

Marine hydrocarbon seeps are cold as distinguished from volcanic, hot seeps; and have two major sources, biogenic or bacterial production of gas, and petrogenic or thermogenic (relating to subsurface petroleum reservoirs) that "leak" to the surface.

hydrothermal biomass
Described as being a biomass between 10,000 and 100,000 times greater than the general abyssal environment.

Just like an oasis in the desert, these toxic sites attract an entire peripheral fauna constituted of sessile crustaceans; such as, the vent barnacles, which resemble a flower, or mobile crustaceans, like spider crabs.

Index of additional Scientific and Technological Topics.