Definition of Terms

 Definition of Terms

There is a lot of technical terms on the Rivers and Streams website. This page is designed to help navigate and define these words and phrases. Use the line below to skip to a certain letter.
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TermDefinition
Abiotic:
not derived from living organisms.
Acreetion:
The gradual addition of new land to old by the deposition of sediment carried by water.
Acidification:
An increase in the acidity of an ecosystem, caused by natural processed or acid deposition.
Acidity:
A measure of hydrogen ion concentration with a pH less than 7.0. See pH.
Acid rain:
Rain having a pH of less than 7.0 can be considered acidic and if it has a pH low enough can potential threaten the life or well-being of vegetation or aquatic systems.
Aeration:
To enhance the oxygen concentration of water.
Aerobic:
Life processes occurring only in the presence of molecular oxygen.
Aggradation:
The geological process in which inorganic materials carried downstream are deposited in streambeds, floodplains, and other water bodies resulting in a rise in bottom elevation. Compare with degradation.
Alkaline:
A measure of hydrogen ion concentration with a pH more than 7.0. See pH.
Alkalinity:
Acid-neutralizing capacity of water usually due to carbonates, bicarbonates, and hydroxides.
Alluvial:
Related to material deposited by running water.
Anadromous:
A life history strategy of fishes that includes migration between fresh- and saltwater. Reproduction occurs in freshwater while growth occurs in the ocean. Compare with catadromous, diadromous, and potamodromous.
Anaerobic:
Life processes that occur in the absence of molecular oxygen.
Anoxic:
A lack of oxygen.
Aquatic:
A term to characterizing growing, living in, frequenting, or pertaining to water.
Aquifer:
An underground layer of earth that contains water or allows for its passage.
Aufwuchs:
Microscopic organisms growing on the bottom of other substrates