Glossary - Freshwater Ecology: Concepts and Environmental Applications - page 488

Commensalism, interspecific interaction in
which one species is influenced positively
and the other is not influenced
Community, all organisms in an area or a group
of species in an area
Compartments, parts of a budget into which
materials are divided; for example, in the
global hydrologic cycle the ocean is a
compartment
Compensation point, light level at which O 2
production by photosynthesis equals con-
sumption by respiration, or CO 2 assimila-
tion is equal to production by respiration
Competition, an interspecific interaction in
which both species harm each other
Competitive exclusion principle, the idea that
only the competitively dominant organism
will survive in an equilibrium environment
Conductivity, the ability of water to conduct
electricity, a function of the number of dis-
solved ions in the water; measured in units
of mhos or Seimens per unit distance
Confined aquifer, an aquifer between two im-
permeable layers (aquifuges)
Consumptive use, a use of water that does not
return it to the stream channel (causes loss
by evaporation or to groundwater)
Control, an experimental condition to which
the treatments are compared.
Core of depression, an area around a well
where the pumping lowers the level of the
groundwater (drawdown)
Coriolis force, a force that induces circulation
in very large lakes; caused by rotation of
the earth
Correlation, a statistical way to measure relat-
edness of two variables; not necessarily
causation
Cosine collectors, sensors used to measure ra-
diation from above
CPOM, see coarse particulate organic matter
Creek, low-order, small stream (crick)
Crenogenic meromixis, differences in density
between waters of monimolimnion and
mixolimnion attributable to below-surface
flows of spring or seep saline water
Critical mixing depth, mixing depth below
which phytoplankton growth does not occur

Cryogenic lake, lake located in a thaw basin of
permanently frozen ground
Cryoperiphyton (kryoperiphyton), periphyton
attached to the bottom of the ice
Cryptorheic, concealed drainage with below-
surface stream flow, usually in limestone,
karstic areas
Cultural eutrophication, nutrient enrichment
caused by humans
Cumulative, a response to numerous events
Cycle, all of the fluxes of a material that occur
in an environment
Cyclomorphosis, successive emergence of dis-
tinctive morphologies in the same species; of-
ten observed in microcrustaceans and rotifers
D L , shoreline development index
Dam, barrier preventing the flowing of water
DAPI, a fluorescent dye specific for DNA used
to count total bacteria using epifluorescent
microscopy or flow cytometry
Darcy's law, a relationship used to calculate
groundwater flow rates
Decomposer, consumes dead organisms
Deflation basin, a basin formed by action of
the wind; can contain a lake or wetland
Degradation, erosion of stream channels; op-
posite of aggradation
Denitrification, conversion of nitrate to N 2 gas
by microorganisms; a form of respiration
that uses nitrate rather than O 2 to oxidize
organic carbon
Density current, current going along the ben-
thos or through a stratified layer; current of
different temperature, ionic strength, or tur-
bidity than the water through which it flows
Density-mediated interactions, interactions ev-
idenced by changes in population size
Detritivores, organisms that eat detritus; also
called saprophytes
Detritus, decaying organic material
Dewatering, removing water from a river or
stream (also abstraction )
Diadromous, migration between fresh and salt
waters
Diagenesis, conversion of sediment into rock