Glossary - Freshwater Ecology: Concepts and Environmental Applications - page 485

deficiency assays and cyanobacterial toxin
bioassays
Alkalinity, acid-neutralizing capacity; the sum of
all titratable bases; usually a function of car-
bonate, bicarbonate, and hydroxide contents.
Allelochemical, a chemical produced by one
species that alters behavior or growth of an-
other species
Allochthonous, originating from outside the
system; often refers to organic carbon
Amensalism, interspecific interaction in which
one species is harmed and the other is not
influenced
Amictic, when a lake almost never mixes
Ammonia gas, NH 3 ; ammonium ion is con-
verted to ammonia gas at basic pH
Ammonification, ammonium (NH 4 ) produced
from organic nitrogenous compounds by
metabolism of living organisms and decom-
position of organic matter
Ammonium, an inorganic N compound; the
ion NH 4
Amphidromous, regular migration from fresh
to salt water (see diadromy ); not for breed-
ing purposes
Anadromous, fish that travel from the ocean
up rivers to breed
Anaerobic, without oxygen; anoxic
Anchor ice, ice that forms on the bottom of
open, flowing streams when temperatures
are below 0°C
Angiosperms, true flowering plants
Anoxic, without oxygen
Anoxygenic photosynthesis, photosynthesis
that does not evolve oxygen, either as cyclic
photophosphorilization or using sulfide as
an electron donor
Anthropogenic, originating from human activity
Aquaculture, the farming of aquatic organisms
Aquiclude, a layer that groundwater flows
through slowly (unsuitable for a well)
Aquifer, permeable deposit that can yield wa-
ter by a well
Aquifuge, an impermeable layer through which
groundwater cannot flow
Archaea, a domain of organisms, unicellular
without organelles; one of three domains (su-

per kingdoms) of organisms; distinguished
on the basis of biochemical and genetic dif-
ferences from the Bacteria and Eukarya
Argillotrophy, a mode of obtaining nutrition in
turbid systems in which the primary source
is organic material associated with clay
particles
Artesian well, a well with water naturally un-
der pressure so it continuously flows from
the wellhead
Ash-free dry mass (AFDM), the mass of mate-
rial that will combust from a dry sample;
used as an estimate of biomass
Assimilation, the process of utilizing nutrients
to synthesize components of a cell
Astatic, unstable; refers to water level
Astrobleme, a meteor crater; lakes can form
in these
Atelomixis, unfinished vertical blending of
stratified water, combining layers of varied
chemical properties without affecting the
hypolimnion
Athalassohaline, saline water having relative
ionic proportions very different from those
of seawater
Atmospheric loading, nutrient input from dry
and wet atmospheric depositions
Attenuation coefficient, a value that indicates
how rapidly light is absorbed
Aufwuchs, see periphyton
Autecology, study of the ecology of a species;
population not community or ecosystem
ecology
Autochthonous, originating within the system
(e.g., organic carbon supplied by primary
producers in the system)
Autofluorescence, natural fluorescence in pig-
ments such as chlorophyll
Autotrophic, the capacity to perform primary
production; self-feeding; able to use CO 2 as
a source of carbon using chemical (chemoau-
totrophy) or light (photoautotrophy) energy
Autotrophic index, chlorophyll:ATP ratio

diversity, between-habitat diversity
Bacteria, a domain of organisms, unicellular
without organelles; one of three domains
(super kingdoms) of organisms; distin-
guished on the basis of biochemical differ-
ences from the Archaea