Census of Marine Life Portal Research Index Past Present Future Unify Past, Present, Future Research Photo Gallery Glossary Links Search this web site Technology Index Transportation to the Study Area Observing and Counting Collecting Organisms Measuring Physical Properties Studying Movement Identifying Cataloging and Analyzing Data Site Map About this site Front Page Census of Marine Life Portal

Front Page > Glossary:

non-living. Abiotic factors include all aspects of climate, geology, and atmosphere that may affect living organisms.

ocean depths greater than 4000 meters. The floor of the deep ocean, from 4000-6000 meters, is called the abyssal plain.

acoustic technology
a technology that utilizes sound in the ocean to "see" underwater. Sound travels through water in waves, with different sizes and frequencies being created by different sounds. A large selection of different acoustic tools are used by scientists, generally involving the emission of sound (from a research vessel or other source) and the recording of its reflection off different surfaces (the ocean floor, fish schools, etc.) in its path. This acoustic technology, commonly used to track submarines, has advanced in recent years and has become a primary tool for oceanographers, both for mapping the physical shape of the ocean floor and for tracking and counting marine animals of all sizes. Applied with other technologies, acoustics are a critical tool for Census scientists.

the study of sound and sound waves. Ocean scientists use acoustic technology to determine their position, map the sea floor, and to track marine animals.

active continental margin
a continental margin that is characterized by tectonic activity, which results from the collision of two tectonic plates, for example, the subduction of an oceanic plate under a continental plate.

small crustaceans that usually live along the coastline or on the seafloor. They are a major component of the benthic community.

the partially melted portion of the upper mantle in the earth's interior. Hot magma from the asthenosphere rises out of the sea floor during submarine volcanic eruptions.

an organism that can meet its cellular energy requirements without eating other organisms. Autotrophic organisms convert inorganic carbon into organic carbon intracellularly (within the cell). This conversion can be accomplished by photosynthesis or chemosynthesis. See heterotrophic.

bacteria and Archaea
microscopic life forms that are single-celled and prokaryotic. They are divided into two distantly related groups, the Eubacteria (or "true" bacteria), and the Archaebacteria (or Archaea). The Archaea are the most ancient form of life on Earth, having existed here for at least 3.5 billion years. Both groups make up two of the three domains of living organisms on Earth, the third being made up of all the Eukaryotes, which collectively comprise the Domain Eukarya.

the study and mapping of sea floor elevations and changes in water depth due to structures that rise up into the water column.

relates to the seafloor. This can refer to a benthic organism or a benthic sample.

the seafloor.

a broad term used to describe the total number of species in an ecosystem, as compared to the total number of individuals. Scientists report on the number of species in the natural world, and they refer to this as the biodiversity of their study area. There are a variety of complex technical definitions of biodiversity.

the study of the geographical range of different species of plants and animals around the world.

the total amount of living material within a given area. Compare to biodiversity. The biomass of a single whale can equal the biomass of many thousands of its planktonic prey belonging to numerous species.

living, biological. Biotic factors that affect organisms include predation, symbiosis, competition, etc.

black smoker
a chimney-like structure formed by the precipitation of minerals at hydrothermal vents, as hot water (up to 400°C) from the earth's mantle is injected into the cold water of the deep ocean.

an organism that derives its energy from chemosynthesis.

a biological process by which an organism uses the energy from the oxidation of inorganic substances such as ammonia, sulfur, and hydrogen to form organic compounds. Unlike photosynthesis, chemosynthesis does not require sunlight, so this process can occur at great depths in the ocean.

the pigment in plants, algae, and phytoplankton that becomes activated by solar energy during photosynthesis. It transfers light energy to electrons.

cold seep
an area of the continental slope where cold fluids leak into the water column. Typically these cold seeps contain high concentrations of methane and sulfide. Water from cold seeps is the same temperature as the surrounding seawater. Cold seeps are called "cold" to contrast them with the hot water from hydrothermal vents. See hydrothermal vent.

all of the organisms that interact, both directly and indirectly, within an ecosystem.

a measure of a substance's ability to conduct heat or transmit electrical current. This conduction of energy is proportional to the total ion content of the water at a given temperature. Since conductivity is then a measure of the total salt (ion) content of the seawater, it is used to determine seawater salinity.

continental margin
the zone of the sea floor reaching from the continents to the abyssal plain, including the continental shelf, the continental slope, and the continental rise.

continental shelf
the zone of the sea floor that stretches from the continent to the continental slope where there is a steep slope to deep water.

continental slope
the area of the sea floor that stretches from the edge of the continental shelf (~200 m) to the abyssal plain (~4000-6000 m). This is a steep slope to deep water.

small crustaceans that feed on phytoplankton. They are a major component of the zooplankton community.

microscopic, single-celled photosynthetic organisms with an external skeleton of silica.

see biodiversity.

deoxyribonucleic acid; a very complex molecule that contains the genetic code for all living things. DNA is the major component of chromosomes within the nucleus of a cell. It largely determines hereditary characteristics.

an ecological unit that includes all the living (biotic) and nonliving (abiotic, or chemical, physical) components that interact in an environment or habitat.

relates to the area on top of the sea floor. Epibenthic organisms may be freely moving or sessile (permanently attached to a surface).

a unicellular or multicellular organism whose cells contain a nucleus and internal cellular bodies (organelles). See prokaryote.

one of the three major groups (called Domains) of life on Earth. It comprises all the eukaryotes, organisms that have a nucleus and discrete organelles in their cells, such as animals, plants and fungus. The other two Domains are Bacteria and Archaea.


Geographic Information System (GIS)
a database that uses spatial and geographic information to create detailed maps. These maps can include anything from the many streams that connect to a river, to the annual rainfall received across a region.

the particular location where an organism or a population lives.

an organism that cannot produce its own energy. A heterotrophic organism must obtain its energy from external sources (by eating other organisms). See autotrophic.

those organisms that spend their entire lives as plankton, such as phytoplankton and zooplankton.

hotspots (or hot spots)
(Biological) Generally locations of high activity, or gathering areas, where animals feed and breed. Species diversity peaks globally at these distinct locations, often located at intermediate latitudes (20-30 degrees North and South) where tropical and temperate species overlap. Hotspots are usually located close to prominent marine geographic features, such as reefs or shelf breaks. These areas seem to be important for many species at once, from plankton to sharks.
(Geological) Areas of the Earth's crust where jets of molten mantle material rise to the surface, forming new crust. One classic example of hot spot activity resulted in the Hawaiian Island chain.

an underwater microphone that will listen to, or pick up, acoustic signals. A hydrophone converts acoustic energy into electrical energy and is used in passive underwater systems to listen only.

hydrothermal vent
an opening in the sea floor occurring near spreading centers in the deep-sea, from which very hot, mineral-rich water from the earth's interior is released. Precipitation of these minerals in the cold water of the deep sea leads to the formation of tall "chimneys", or black smokers. Vents are home to many unusual creatures, many of which use chemosynthesis or symbiosis to obtain their nutrition.
Hydrothermal vents & seeps, seeps are similar to vents, but are generally much cooler and often don't have as high a level of biodiversity.

in situ
a Latin term referring to something in its original place.

the space between adjacent particles (such as sand grains) within soft sediments. The animals that live in these spaces are usually part of the benthic meiofauna (very small animals living in sea floor sediments).

the coastal marine zone between high and low tide; also called the littoral zone


small crustaceans, similar to shrimp, that make up a very large amount of the biomass in the oceans and are a very important part of marine food webs. Krill are found in huge masses in polar waters and are the main food for baleen whales.

the immature form of an animal. Often, in the ocean, larvae are planktonic.

the rigid top layer of the earth that includes the crust (see tectonic plate) and the upper mantle. See asthenosphere.

the zone on a shoreline between mean high tide and mean low tide, also referred to as the intertidal zone.

typically refers to larger animals that can be seen without a microscope. Organisms in the macrofauna are usually larger than 1 mm in size.

the largest layer of the earth's interior, reaching from the crust and the core to a depth of 2891 km.

refers to animals greater than 20 cm in size. Megafauna are found in the benthos as well as open water.

benthic organisms between 0.06 and 0.5 mm. This size fraction is dominated by interstitial animals.

those animals that spend part of their life cycle in the plankton but become part of the nekton or benthos as adults, such as some larval fish and crabs. See holoplankton.

multicellular organism with eukaryotic cells (those containing genetic material in the nucleus).

microscopic life forms, particularly bacteria, archaea, protists and viruses. Despite their minute size, they make the greatest contribution to ocean biomass.

a patterned movement of organisms that usually covers large relative distances. Ex.: Plankton can move up and down in the water column over the course of a day and whales can move around an ocean over a season.

a benthic organism that can move through the sediments of the sea bottom or across the surface of those sediments. See sessile.

free-swimming animals that control their own direction in the water column, such as fish. See plankton and benthos.

refers to shallow-water marine environments, from the shoreline to the edge of the continental shelf.

the study of the world's oceans, including physical, chemical, geologic and biological aspects.

any type of individual living being, whether plant, animal, protist (such as an alga), fungus, or bacteria.

passive continental margin
borders a growing ocean basin. There is no tectonic activity at these margins.

refers to all marine environments, including neritic and oceanic (open ocean) areas.

process by which plants use the sun's energy to convert inorganic carbon dioxide and water into organic carbon molecules (glucose) and oxygen.

floating microscopic plants that obtain their energetic requirements through photosynthesis.

small aquatic organisms whose direction is controlled by water movements. Plankton may be able to swim by means of flagella or other appendages, but they are not strong enough to swim against a current.

an organism that spends part or all of its life cycle in the plankton. See meroplankton and holoplankton.

a group of individuals of one species, found within a particular area.

a single-celled organism whose cell lacks a nucleus and internal cellular bodies (organelles). See eukaryote.

single-celled, eukaryotic organisms. May be autotrophic or heterotrophic.

a sampling unit used to measure the number of individuals within a specific area.

data that is measured or recorded using amounts, abundances or occurrences, rather than descriptions as with qualitative data.

single-celled heterotrophic organisms with elaborate skeletons made of silica. These silica skeletons are so durable that radiolarian fossils are used to date deep-sea sediments.

a major area of the Earth, with similar physical characteristics, comprised of numerous habitats. Ex.: The abyssal plain of the world's oceans.

the total amount of salt dissolved in seawater; the units most often used are parts per thousand (ppt) but practical salinity unit (psu) is now the accepted standard in oceanography. An average salinity value for seawater is 35 ppt (psu) or 35 parts of salt in 1000 parts of water.

an isolated, steep-sided, peak on the seafloor usually caused by volcanic activity. Generally, seamounts rise at least 1000m, though biologists often include shorter submarine peaks.

particulate organic and inorganic matter that accumulates in loose form on the sea floor.

an organism that does not move, but stays attached to one place on the sea floor, such as a mussel or a sea fan. As planktonic larvae, these animals float with the currents until they reach a suitable spot to settle onto the sea floor. See motile.

a shallow location, such as over a sandbank, often home to large numbers of schooling fish. These schools of fish are sometimes called shoals themselves.

a juvenile salmon about two years old, the age where it migrates from its freshwater spawning ground out to the ocean.

an acronym for sound navigation and ranging equipment. SONAR systems use sound waves to detect underwater objects by listening to the returning echoes. The distance to the object or the seafloor can be calculated by measuring the time between when the signal is sent out and when the reflected sound, or echo, is received.

a group of organisms that breed with each other to produce fertile offspring.

subduction zone
an area of the sea floor where two tectonic plates are moving toward each other, causing the more dense, or heavier plate to be forced (or subducted) underneath the less dense, or lighter plate.

the marine zone below the intertidal zone that remains submerged at low tide; generally only refers to near-shore or coastal areas

a long-term, close, association between two individuals of different species that is a benefit to both ("mutualism"), a benefit to one at a cost to the other ("parasitism"), or a benefit to one with no effect on the other individual ("commensalism").

a field of science that seeks to identify and categorize organisms, in order to determine where an organism fits in a broad biological classification system.

a scientist who studies the biological classification (taxonomy) of organisms and identifies species.

refers to any geological process that involves movement or deformation of the earth's crust.

tectonic plate
slabs of the earth's rigid lithosphere, which move independently on top of the asthenosphere. Each of these plates is made up of dense oceanic crust or lighter continental crust. See subduction zone.

pattern of elevation of the Earth's surface including the ocean bottom. A topographic map displays surface features.

a pre-established line or zone used for sampling biological communities.

the use of three or more fixed points, such as receiver buoys or satellites in orbit around the earth, to pinpoint the location of an object. This is the process by which the Global Positioning System (GPS) and tracking of some types of tagged animals work.


extremely small and simple microbes. They are nothing more than a small segment of DNA surrounded by a protective shell. Viruses cannot reproduce on their own, they must take over the normal cell reproduction of another living host.

water column
the entire depth of a water body, from its surface to the bottom.



animal plankton, such as copepods and jellyfish. See phytoplankton.

top of page

Website maintained by
Office Of Marine Programs
University of Rhode Island

E-mail comments about the web site to