A-E

Abundance
Total numbers of individual animals, or of taxonomic groups of animals.

Antifouling
Substances applied to the hulls of vessels to prevent attachment and growth of marine organisms that could affect the performance of the vessels and introduce exotic marine organisms.

Barnacle
A type of encrusting arthropod, barnacles attach themselves permanently to a hard substrate, mostly in shallow and intertidal waters, but also on floating objects and the deep sea.

Bathymetry
Bathymetry is the study of underwater depth.  A bathymetric map or chart usually shows floor relief or terrain as contour lines (called depth contours).

Bathypelagic Zone
The region of an ocean below 1,000 metres in depth.  No light penetrates this zone.

Bioaccumulation
The process whereby certain substances such as pesticides or heavy metals increase in concentration within the tissues or internal organs of organisms as they are transferred up the food chain. For example, the substances are absorbed in plants, then eaten by aquatic organisms such as fish, which in turn are eaten by predators, and then eaten by larger predators or humans. 

Biogenous
Producing or produced by living things (adj.).

Bioluminescence
The production and emission of light by a living organism as the result of a chemical reaction during which chemical energy is converted to light energy.

Bivalve
Molluscs belonging to the class Bivalvia.  They have two-part shells, and typically both valves are symmetrical along the hinge line.

Caldera
A volcanic feature formed by the collapse of land following a volcanic eruption.

Cetacean
The Cetacea are one of the most distinctive and highly-specialized orders of mammals. They include the blue whale, dolphin, narwhal, blind river dolphin and singing humpback whale.

Chemosynthesis
The synthesis of organic compounds by bacteria or other living organisms using energy derived from reactions involving inorganic chemicals, typically in the absence of sunlight.

Chemotrophic
The derivation of energy by organisms, not from the sun but from the oxidation of molecules in their environment (in the present case, from inorganic H₂S molecules).

Chimney
A structure on the seafloor that forms when hot hydrothermal fluids vent in cold seawater and sulphide materials precipitate on the edges of a conduit.

Convection
Heat transfer in a gas or liquid by the circulation of currents from one region to another.

Crust
The outermost and thinnest of the Earth's compositional layers. The crust consists of rocky material that is less dense than the rocks of the mantle below. The continents make up the continental crust, and the crust beneath the oceans is the oceanic crust. The oceanic crust varies in thickness from 6 to 8 kilometres, and the continental crust varies in thickness from 30 to 70 kilometres.

Density
With respect to animals, the numbers (of individuals or taxa) per unit area.

Diversity
A statistical index describing, in combination, the numbers of individuals representing the numbers of species within a sample or location.

Dobson Unit
The Dobson unit ("DU") is defined to be 0.01 mm thickness at STP ("Standard Temperature and Pressure").  Ozone layer thickness is expressed in terms of DUs, which measure what its physical thickness would be if compressed in the Earth's atmosphere.

EIA
Environmental Impact Assessment.

EIS
Environmental Impact Statement.

Epifaunal
Living on and in association with other animals (but not parasitic).

Epipelagic Zone
The region of an ocean extending from the surface to a depth of about 200 metres.  Light penetrates this zone, allowing photosynthesis.

Euphotic Zone
The upper region of an ocean that receives light, making photosynthesis possible.