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)

plankton (literally, "wanderers")
The weakly swimming organisms that live in the water column and drift with the currents.

Plankton range in size from viruses and micron-sized bacteria to single-celled algae and protists (generally less than 200 micrometers) to small crustaceans (generally up to a few millimeters), the krill, extending to a few centimeters, and jelly fish, which may be meters long.

The very long geological period extending from the earth's formation to the Cambrian Period, marked by the appearance in abundance of life, now recorded in fossils.
prokaryotes (literally, "pre-nuclear")
The group of organisms (bacteria and archaea) without a true nucleus.
Single-celled eukaryotic organisms (as, distinguished from the bacteria), now generally considered to comprise their own kingdom, alongside the plants and the animals.

Members of this group, traditionally known as the Protozoa, are key grazers on the smaller phytoplankton.

pycnoclines (literally "density slope")
Gradients in density through the water column.

Differences in density between water types are created by differences in their temperature and salt content; cooler, saltier water is more dense.

Pynoclines often coincide with thermoclines (vertical temperature gradients), but can also arise from differences in the salt content between water types.

residence time
The average length of time an entity remains in a particular part of its cycle; for example, the residence time of water in the deep ocean is the average time a water parcel remains in the deep sea.

The term is often used in environmental chemistry to denote the length of time an ion or compound remains in the atmosphere or surface waters.

Riftia pachyptila, giant tube worm
Giant, colored worm-like creatures living around hydrothermal vents in the eastern Pacific.

They live in symbiosis with the chemosynthetic bacteria that provide the worms with their nutrition. It took the scientific specialists awhile to understand the functioning of the animal, which at first they believed to be a filter feeder.

At first they were described as having no eyes, no mouth, or any other obvious organs for ingesting food or secreting waste, and no means of locomotion. It was not a worm, a snake, nor an eel, but it wasn't a plant either.

Gelatinous filter feeders, at times important phytoplankton grazers.

Their transparent bodies are barrel-shaped, open at both ends; they draw water in at one end and expel it at the other end as they move through the water.

Salps, along with the larvaceans, are protochordates.

Steep-sided sub-surface mountains, usually conical or elliptical in shape and of volcanic origin.
sibling species
Closely related species that have recently diverged from each other through evolution.
species diversity
With reference to a biological community, the number of species and the relative evenness of their abundance.
species richness
The number of species in a community or set of samples.
A local fish population and ideally, the basic unit managed in fisheries.

A stock is a breeding unit, defined by having its own time and place for spawning, and its own pattern of migration to and from nursery, feeding, and spawning grounds.

Stocks can generally be differentiated genetically, morphologically, or based on other differences.

The downward movement of one crustal plate beneath another, typically occurring within the deep ocean trenches.
suspension feeders
Invertebrates; such as, corals, clams, or sponges that feed on prey or detritus suspended in the water.

Index of additional Scientific and Technological Topics.