DDT	Dichlorodiphenyltrichloroethane; a colourless odourless substance used as an insecticide.
decomposing bacteria	Micro-organisms which acquire the energy they need through the oxidation of organic material.
decomposition	The degradation of organic matter into simple organic and inorganic compounds, with consequent liberation of energy.
deficiency	The state or quality of being deficient.
defoliate	To deprive (a plant) of its leaves.
degradation	A reduction in worth, strength or quality.
density	1. The degree to which something is filled or occupied 2. The measure of a compactness of a substance expresses as its mass per unit volume In oceanography, the density of sea water is numerically equivalent to specific gravity and is a function of salinity, temperature, and pressure.
depletion	Entire or partial emptying.
deposit feeder	An organism feeding on organic material contained in the soft sediments of the sea bottom. May be selective or non-selective depending on their ability to select the type and size of particles they swallow.
depth	The distance downwards, backwards or inwards.
desiccation	Removal of water; dehydration.
deterioration	Making or becoming worse; depreciation.
detritus	Accumulated organic debris from dead organisms, often an important source of nutrients in a food web.
diffusion	Dispersal or spreading of matter down a concentration gradient, i.e., from a higher concentration to a lower concentration.
discharge	To pour forth or cause to pour forth.
disintegration	The act or state of disintegrating; separating into parts; breaking up.
dispersal	Spread of a species to a new location. In many organisms, this happens at a particular stage in the life cycle, and is often crucial to the survival of the species. Organisms may disperse as spores, seeds, eggs, larvae, or adults.
dispersant	Chemical or physical agents used to disperse or distribute materials. Often used in the control of pollutants such as oil. A side effect may be the promotion of more effective contact between the pollutants and the organism.
dissolved oxygen	The amount of oxygen, O2 , in solution under existing atmospheric pressure and temperature.
disturbance	1. Being disturbed 2. An interruption or intrusion.
diurnal	Having a period or cycle of approximately one day.
DNA transcription	The formation of an RNA molecule upon a DNA template by complementary base pairing; mediated by RNA polymerase.
domestic sewage	Waste matter from domestic or industrial establishments.
dump	1. To empty (objects or materials) out of a container 2. To unload or empty (a container) as by overturning.