Title: Glossary of limnological terms
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Title: Glossary of limnological terms
Physical Description: Book
Creator: Batterson, Ted R.
Publisher: Agricultural Research and Education Center, IFAS, University of Florida
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Full Text

3t r-v

AREC Ft. Lauderdale Research Report FL-82-3


of Limnological Terms

Ted R.

ILF.A.S Imri. of Fiii

I.F.A.S.-Univ. of Florida

Institute of

Food and Agricultural


University of


June 1982

Limnology is the study of freshwater systems.
It is a science which incorporates a number
of disciplines including biology, chemistry,
physics, and mathematics. Because it encom-
passes so many areas it includes many terms.
To understand or effectively communicate in
limnology, one needs to be familiar with the
terminology. That is the reason the follow-
ing list was compiled. It is hoped that it
can be used as a reference material by those
persons who are beginning to study limnology
or aquatic ecology, allowing them to escape
the problem of becoming bogged down by the

abiogenic not produced by the action of living organisms

absolute oxygen deficit difference between the observed oxygen concentra-
tion in the water and the saturation value at 40C at the pressure of
the lake surface

absorbance (A) the logarithm of the reciprocal of transmittance (T):

A = log = -log T

absorption lessening of light energy with depth by transformation to heat

acre a unit of area equal to 43,650 ft2, 4047 m2 or 0.4047 ha

acre-foot amount of water needed to cover an acre to a depth of one foot;
it is equal to 43,650 ft3

actual oxygen deficit difference between the oxygen content observed at
any depth and the saturation value of that same quantity of water at
its observed temperature at the pressure of the lake surface

ADP adenosine diphosphate; see ATP

adsorption a type of adhesion which occurs at the surface of a solid or a
liquid in contact with another medium, resulting in an increased con-
centration of molecules of that medium in the immediate vicinity of
the surface of the solid or liquid

aerobic living or active only in the presence of oxygen

AFDW see ash-free dry weight

akinete a thick-walled, reproductive spore peculiar to the blue-green
algae. It is formed by the modification of a vegetative cell in which
proteinaceous reserves in the form of cyanophycin granules are accumu-

algae simple, photosynthetic plants with unicellular organs of reproduction
and not possessing true roots, stems or leaves

alkalinity is the capacity of water to accept protons and represents the
buffering --pacity of'natural waters. Typically the alkalinity of
many surface waters is primarily a function of carbonate (CO3),
bicarbonate (HC03-), and hydroxide (OH-) and therefore, is an indication
of the concentration of these constituents. However, the measured values
may also include contributions from borates, phosphates, sulfates, or
silicates if these are present

allochthonous arising within another biotope (Gr.-allos=other; chton=land)

allometry the study of the change in proportion of various parts of an
organism as a consequence of growth

alluvial composed of alluvium, which is sediment deposited by flowing water

amictic lakes lakes that do not undergo turnover, such lakes are sealed
off constantly by ice from most of the annual variations in temperature

amplitude the difference in height between the highest and lowest part of
a wave

anabolic one aspect of metabolic processes in which organisms synthesize
complex molecules from simpler ones; compare catabolic

anerobic living or active in the absence of free oxygen; may be obligate
or facultative

angstrom (A) metric unit of measurement equal to 10-10 m
anion an ion with a negative electrical charge

anisogamy condition in which the gametes differ in size or motility and
the larger or less active gamete (deemed the female) generally absorbs
the other smaller or active gamete (deemed the male)

anoxia deficiency of oxygen in the tissues
anthropocentric interpreting reality exclusively in terms of human values
and experiences

antibiotic chemical substance produced by an organism that inhibits the
growth of another organism or itself

aplanospores non-motile asexual spores found in certain algae and fungi
arheic regions hydrological regions within which no rivers arise. They
are desert areas that occur in the latitudes of the trade winds and
between which lies the zone of equatorial rains

ash-free dry weight (AFDW) is the organic (ash-free) weight of a substance
after it has been ignited at 5500C

assay to examine by trial or experiment; put to a test; qualitative or
quantitative determination of the components of a material

atmospheric pressure is the pressure at any point in an atmosphere due
solely to the weight of the atmospheric gases above the point concerned.
Also known as barometric pressure. One atmospheree (1 atm) is the amount
of pressure that will support a column of mercury, (in a barometer) 76 cm
high at 00C. The pressure is equal to 14.7 pounds per square inch (psi).
Approximately one atmosphere is gained for each 10 meters of water depth

ATP adenosine triphosphate. A chemical that provides a common source of
energy for a range of different cellular activities. Orne of the three
phosphate groupings is readily transferred to other substances by enzyme
activity, releasing a considerable amount of energy. ATP is formed from
the addition of a phosphate (P04-) to ADP utilizing light energy captured
during photosynthesis or energy derived from catabolic processes


attenuation generally, reduction in strength, size, quantity; lessening of
radiation intensity due to absorption and scattering

aufwuchs the community of organisms that are firmly attached to, or move
upon, a substrate but do not penetrate into it. This is a German term
that has a much broader meaning than periphyton, the nearest English

autochthonous arising within the biotope under consideration (Gr.-autos=
self; chthon=land)

autotroph an organism that can provide its own nourishment, usually by the
production of organic matter through the processes of photosynthesis

auxospores in diatoms, large cells which develop from newly formed zygotes

auxotrophic organisms requiring an external supply of organic compounds
(such as vitamins) for their growth and maintenance

baroclinity the state of stratification in a fluid in which surfaces of
constant pressure (isobaric surfaces) intersect surfaces of constant
density (isoteric surfaces)

barometric pressure see atmospheric pressure

basalt a dark-colored microcrystalline volcanic rock notable for the columnar
forms in which it is often found

bathymetric measurement of the depth of large bodies of water

Beer's Law the law which states that the absorption of light by a solution
changes exponentially with the concentration, all else remaining constant

Beer-Lambert Law see Eouger-Lambert-Beer Law

benthos organisms that live in or on the sediments

biliproteins (biloproteins) a pigment-protein complex in which water-soluble
pigments cannot be separated from a protein moiety. Like carotene they
assist in photosynthesis by transferring light energy that they absorb to
chlorophyll. Structurally they are similar to bile pigments in animals
and were originally named phycobilins

bioassay quantitative estimation of biologically active substances by the
amount of their actions in standardized conditions on living organisms
or parts of organisms

biogenic -, produced by the actions of living organisms

biogenic meromixis the condition in which there is only a partial mixing
of a lake since a monimolimnion is formed in the lower stratum of
water which is the consequence of biological origin. The monimolimnion
is formed as the result of the accumulation of salts which are either
liberated from the decomposition of sedimentary organic matter or the
settling-out of organic matter from upper layers of water

biomass the weight of all living (or organic) material in a unit area at
a given instance in time

biota animal and plant life (fauna and flora, respectively) characterizing
a given region

biotope a geographic region in which the environment is suitable for life

Birgean percentile absorption of light the reduction in irradiance at a
given depth in the water column expressed as a percentage of what amount
of irradiance is impinging on the water surface. It is defined by the
following equation:
100 x (o Iz)
0 x

where Io = irradiance at the lake surface
I = irradiance at depth z, usually taken at 1 m intervals
bloom a profuse growth of microscopic or semi-microscopic algae which may
discolor the water, make it turbid, and many times cause it to be
foul-smelling; usually of short duration but in some instances may be

Bouger-Lambert-Beer Law the intensity of a beam of monochromatic radiation
in an absorbing medium decreases exponentially with penetration distance.
Also known as the Beer-Lambert and Lambert-Beer Law

Boyle's Law expresses the isothermal pressure-volume relation for a body
of ideal gas. If temperature is held constant, the volume (V) of a
given mass of gas is inversely proportional to the pressure (P)
exerted upon it, or has a constant product (C). That is:
PV = C

Boyle-Charles' Law (or Ideal Gas Law) the product of the pressure and
volume of a gas is a constant (Boyle's Law) which depends jn the
temperature. Stated mathematically as:

P1V1 = P2V2
T1 T2
where: P1 and V1 are the pressure and volume of a body of gas at temperature
T1 (in "K), and
P2 and V2 are the pressure and volume of the same body of gas
at temperature T2 (in OK)

brackish somewhat salty; less salt than seawater

breaker the collapse of water over the front of an asymmetrical and unstable
wave. They occur in an array of types ranging between two extremes which
are plunging breakers and spilling breakers
C4 is the radioactive isotope of carbon which has the atomic weight of 14

C-3 name given to plant species in which the primary initial CO fixation
product is mostly a phosphorylated three-carbon acid called 3-phosphogylceric
acid (3-PGA). It is the initial reaction of the Calvin cycle. Most
plants are C-3 species

C-4 name given to plant species in which the primary initial CO2 fixation
products are the four-carbon aspartic and malic acids. The reaction
by which CO2 (actually HCO -) is converted to the four-carbon acids
is through the initial combination with phosphoenolpyruvic acid (PEP)
to oxaloacetic acid. Most C-4 species are monocots but a few are
dicots. See Kranz anatomy

calcareous resembling, containing or composed of calcium carbonate (CaCO3)

calciphobic intolerant of high calcium levels

caldera basin formed by the subsidence of the roof a a partially emptied
magmatic chamber. A more or less circular volcanic depression whose
diameter is many times greater than that of the volcanic dent

Calvin cycle the sequence of reactions leading from the incorporation of
CO2 to the more complex organic products produced in photosynthesis
carotenes see carotenoid

carotenoid a class of yellow, orange, and red plant pigments located in
chloroplasts and in plastids in other plant parts where chlorophyll is
absent. Not essential to, but assists in photosynthesis by absorbing
light and passing the energy on to chlorophyll. There are two kinds
of carotenoids, carotenes and xanthophylls. Carotenes are orange-
yellow to red pigments which are linear unsaturated hydrocarbons that
are converted to vitamin A in the animal liver. Xanthophylls are
yellow pigments which are oxygenated derivatives of the linear
unsaturated hydrocarbons of carotenes

catabolic'- one of the two aspects of metabolic processes in which an
organism breaks down (degrades) complex organix molecules into simpler
ones with an associated release of energy

cation an ion with a positive electrical charge

centric diatoms (Centrales) a grouping of diatoms that exhibit radial
symmetry, meaning they are capable of being halved in either of two
(or more) planes so that the halves are apparently or approximately
mirror images of each other

chelating agent organic compounds which have a heterocyclic ring containing
a metal ion attached by coordinate bonds to at least two non-metal ions
in the same molecule

chelation to form a stable ring compound by joining a chelating agent to a
metal ion

chemocline a term specific to meromictic lakes which refers to the stratum
of water between the upper statum of water (mixolimnion) and the lower
stratum (monimolimnion) and is characterized by a steep salinity

chitin an insoluble carbohydrate commonly found in the exoskeleton of
insects and other arthropods; it also occurs in the cell walls of
some algae

chlorophyll the generic name for any of several oil-solube green tetrapyr-
role plant pigments which function as photoreceptors of light energy
for photosynthesis

chromatophores (chromoplasts) pigmented plastids of plant cells

cirque a steep hollow, often containing a small lake, occurring at the upper
end of some mountain valley

clinograde curve of temperature or of a chemical substance in water that
exhibits a uniform slope.(either positive or negative) from the
surface downward into deeper water (Gr.-klinein=slope)

clinograde oxygen profile is where the oxygen concentration is depleted in
the lower depths of water

closed lakes a lake with no outflow

coccoid spherical or more literally "sphere-like" in shape

coefficient of eddy diffusion (A) is a measure of the rate of or intensity of
mixing (exchange) across a fluid plane. Important to note the A is
inversely proportional to stability, i.e. as stability increases, A

color a general term that refers to the wavelength composition of light,
with particular reference to its visual appearance

commensalism of members of different populations living in close association
in which one population is benefited and the other is not affected

conduction transmission of energy by a medium which does not involve
movement of the medium itself

conductivity the ratio of the electric current density to the electric
field in a material

convection transmission of energy or mass by a medium involving movement
of the medium itself

copepods any of numerous small marine or freshwater crustaceans of the
sub-class Copepoda which is in the class Crustacea

Coriolis effect (or force) the diverting force of the earth's rotation
which causes horizontally moving water or air particles to be diverted
towards the right in the Northern Hemisphere and towards the left in
the Southern Hemisphere

coulomb a unit % electricity; a quantity of electricity equal to the charge
on 6.25 x 10 electrons; the quantity given by one ampere in one second

crop total weight of organic matter removed from a given area over a period
of time in the course of normal harvesting

cryogenic lakes Arctic lakes formed from the effects of permafrost

currents nonperiodic water movements generated by external forces which in-
clude the frictional exertion of wind stress, changes in atmospheric
pressure, horizontal density gradients caused by differential heating
or by diffusion of dissolved materials from the sediments, and the
influx of water to a lake in relation to retention time and outflow

cyanophycin granules proteinaceous granular storage products found in
blue-green algal cells

cycloid circular path or orbit

cyclomorphosis periodically repeated changes in the body form of successive
generations of planktonic animals

cyclonic having a sense of rotation about the local vertical that is the
same as the earth's rotation: as viewed from above, counterclockwise
in the Northern Hemisphere, clockwise in the Southern Hemisphere and
undefined at the Equator

Dalton's Law of Partial Pressures the pressure of a mixture of gases is
the sum of the partial pressures of the component gases. This is
because it is characteristic of a mixture of gases that the component
gases in many respects behave completely independent of one another

deltaic lakes lakes formed in the areas of a river delta

dendritic tree-shaped or branching

density mass per unit volume, usually given in grams per cubic centimeter;
see specific gravity

depth-area curve see hypsographic curve

depth-volume curve represents the relationship of lake volume to depth.
The units of expression can be either in percent of the total lake
volume above a specific depth or in volume units versus depth

detritus finely divided settleable material suspended in the water: organic
detritus arises from the decomposition of the broken-down remains of
organisms; inorganic detritus is the settleable mineral materials

diapause a period during which growth or development is suspended, accompanied
by greatly decreased metabolism

dichotomy branching which is characterized by successive forkings into two
approximately equal divisions

dimictic lakes lakes that circulate freely twice a year in the spring and
fall and are directly stratified in summer and inversely stratified
in winter

dioecious male and female gametes are derived from different individuals

diploid cells which have pairs of chromosomes, or twice the haploid number (2n)

dipole in physics, a configuration in which a positive and a negative
charge of equal strength are separated by a specified distance

diurnal pertaining to or occurring in a day or each day; daily. Occurring
or active during the daytime rather than at night

divalent in chemistry, elements having a valence state of two

doline a particular kind of solution lake that is very circular and
conically shaped

drainage basin (catchment area) in America, equivalent to watershed,
which is the region or area drained by a river. In Europe, watershed
refers to the ridge or crestline dividing two drainage areas

dry weight the weight of an organism after having been dried to a constant
weight at some specified temperature. Temperatures that have been
commonly used range from 600 to 105C

dune lakes wind created lakes in arid regions formed by deflation or
erosion of broken rock, or by the redistribution of sand

dyne unit of force, equal to the force which imparts an acceleration
of 1 cm sec-2 to a 1 gram mass

dystrophic brown-water lakes with a very low lime content and a very high
humus content, often characterized by a severe poverty of nutrients

ectogenic meromixis a condition that results when some external event
brings salt water into a freshwater lake or fresh water into a saline
lake, resulting in a superficial layer of less dense, less saline
stratum overlying a monimolimnion of denser more saline water

eddy rotating region of fluid

effluent something that flows out or forth

egress a place or means of exit; an outlet

Einstein (E)-is defined as the number of quanta (photons) equal to Avogadro's
number (6.02 x 1023); that is, the number of quanta per molar volume

Ekman spiral a theoretical representation that a wind blowing steadily over
an ocean of unlimited depth and extent and uniform viscosity would cause,
in the Northern Hemisphere, the immediate surface water to drift at an
angle of 450 to the right of the wind direction, and the water beneath to
drift further to the right and with slower and slower speeds as one goes
to greater depths

electromagnetic wave a propagating, oscillatory combination of an electric
and a magnetic field resulting from the acceleration of an electric
charge; a transverse wave whose electrical component is perpendicular
to a magnetic component

endemic taxa which have a restricted range within a given region and the
distributional range is smaller than the geographic area under consider-

endogenous produced from within; originating within

endorheic regions hydrological regions within which rivers arise but never
reach the sea. They occur between subtropical deserts and the tropical
and temperate humid regions

enthalpy the sum of the internal energy of a system plus the product of the
system's volume multiplied by the pressure exerted on the system by its
surroundings. Also known as heat content

entrainment the transfer of fluid by friction from one water mass to another,
usually occurring between currents moving in respect to each other;
pulled or drawn along after itself

epilimnion the turbulent superficial layer of a lake lying above the
metalimnion which does not have permanent stratification (Gr.-epi=on;

epilithic growing on or upon rock surfaces

epineuston organisms adapted to living on the upper surface of an interface

epiphytes organisms that use plants as a substrata without penetrating into
them and without withdrawing nutrient substances from them

epitheca see frustule

eukaryotes eucaryotess) are organisms composed of eukaryotic cells. Where
eukaryotic cells are distinguished by having the following:

1 the nucleus separated from the cytoplasm by a nuclear membrane
and the genetic material borne on a number of chromosomes that
consist of DNA and protein
2 nuclear division by mitosis
3 cytoplasmic inclusions are membrane bounded organelles;

compare prokaryotes

euphotic zone stratum of a lake into which sufficient light penetrates for
active photosynthesis to take place; compare trophogenic zone

euryhaline able to tolerate a wide range of salinity (Gr.-euru=wide); compare

eutrophic a multi-defined term usually implying a water body well supplied
with nutrients and highly productive in terms of the formation of
organic matter (Gr.-eu=well; trophein=to nourish)

evaporation conversion of a liquid to the vapor state

evapotranspiration water loss due to both evaporation and transpiration

exogenous derived from or developed from external causes

exorheic regions hydrological regions within which rivers originate and
from which they flow to the sea. This regional type contains the major
lake districts of the world and most lakes

exponential growth phase (log phase of growth) is the time when the increase
of the members of a population is changing exponentially. Mathematically
it is written as:
dN = rN

which states that the rate of increase of N (the number of organisms)
with time is equal to r (the intrinsic rate of increase of the
population) times N; where r is a constant and is defined as being
equal to (b-d) and b is +*e birth rate and d the death rate of the

extinction coefficient (n) is the constant a in the Beer's Law relation:
A = abc, where A is the absorbance, b the path length, and c the
concentration of the solution. [ow called absorptivity but formerly
known as the absorbancy index, absorption constant, or extinction

extinction coefficient, total (n ) is the extinction coefficient for
naturally occurring lake water which is defined as:

nt = n + np + nc

Where: nt = natural total extinction coefficient
n = extinction coefficient of the water itself
n" = extinction coefficient due to the particles suspended in
the water
nc = extinction coefficient due to the dissolved compounds or
color in the water

facultative capable of altering responses to varying environmental
conditions; compare obligate

fall turnover is the autumnal period of circulation of a water body

fermentation a group of chemical reactions induced by living or non-
living ferments (things that cause fermentation, i.e. yeast, bacteria,
mold, enzymes) that split complex organic molecules into relatively
simple substances; especially the anaerobic conversion of sugar to CO2
and alcohol by yeast

fetch distance over which the wind has blown uninterrupted by land

filament a type of thallus consisting of one or more rows of cells, with
or without a mucilaginous sheath

fjord (fiord) a narrow, deep inlet of the sea between high, cliffs or
steep slopes
fluvial pertaining to a river or stream, formed or produced by the action
of flowing water

form resistance is the decrease in sinking rate of a cell (V in Stoke's
Law) caused by the shape of the alga relative to that of a sphere of
equal density and volume

frequency (v) the number of wave crests (peaks in energy) passing a given
point in a given interval of time. The frequency is equal to the
velocity of light (c) divided by the wavelength (X):

v = c

fresh weight is the weight of an organism without water adhering to it,
equivalent to wet weight

frustule a diatom cell wall consisting of two halves or valves. The
upper valve is termed the epitheca, the lower valve the hypotheca

geostrophic pertaining to the deflecting force that results from the earth's

gross productivity (rate of gross production)- it is the observed or measured
change in biomass, plus all predatory and non-predatory (respiration,
excretion, death, or injury) losses divided by the time interval

gyrals or swirls, are the patterns by which the surface currents of
very large bodies of water circulate

haploid cells containing only a single set of chromosomes, or n number of

hard waters waters containing large concentrations of alkaline earths
derived from drainage of calcareous deposits. Usually taken as
being greater than 100 mg CaC03 L-1 total hardness

hardness originally a measure of the capacity of water to precipitate
soap. Dissolved cations in the water combine with soap to form
insoluble precipitates and delay the formation of lather. Precipitated
materials from such hard water also form scale in vessels in which the
water is heated. This effect is caused primarily by the salts of
calcium and magnesium. Other polyvalent cations may also precipitate
soap (e.g.-Al, Fe, Mn, Zn, and Sr) but their concentrations in most
waters are insignificant compared to Ca and Mg

heat budget, annual (QA) total amount of heat necessary to raise the
water from the minimum temperature of winter to the maximum summer

heat content of a body of water is the amount of heat that would be released
on cooling from its maximum temperature to 0C

heat income, summer (GS) amount of heat necessary to raise the temperature
of the lake from an isothermal condition at 40C to the maximum
observed heat content

heat income, winter (9W) amount of heat necessary to raise the temperature
of the lake from its minimum heat content to 4C

hectare (ha) a metric unit of area equal to 10,000 m2. A hectare equals
2.471 acres

Henry's Law states that the mass of any gas which will dissolve in a given
volume of liquid is directly proportional to the pressure of the gas
(provided that the temperature remains unchanged)

heterocysts specialized vegetative cells unique to blue-green algae,
that develop a thick envelope over the cell wall except at the polar
regions, in which the heterocyst is connected to adjacent vegetative
cells by a pore channel. They lack phycobillins and an oxygen evolving
photosystem and they are major sites of nitrogen fixation under aerobic

heterograde a curve for temperature or a chemical factor in a body of water
that exhibits a non-uniform slope from the surface downward into
deeper water (Gr.-heteros=other)

heterotroph an organism which requires a supply of organic material from
its environment for its metabolism

holomictic lakes lakes that are completely circulated

holoplanktonic composite of perennial species that are present throughout
the year

hormogonia short, slightly modified lengths of trichomes without differenti-
ated cells that fragment from the parent trichome and that move by means
of a gliding motion, they can develop into a new filament. It is a
means of vegetative reproduction in blue-green algae

humic acids any of various complex organic acids obtained from humus;
insoluble in acids and organic solvents

humus the amorphous, ordinarily dark-colored, colloidal matter in soil, a
complex of the fractions of organic matter of plant, animal, and micro-
bial origin that are most resistant to decomposition

hydrostatic pressure is the pressure at a point in a fluid at rest due to
the weight of the fluid above it

hypereutrophy excessive eutrophy, extremely eutrophic

hypervolume see niche

hypolimnion the deep layer of a lake lying below the metalimnion and
removed from the surface influences (Gr.-hypo=below, under)

hyponeuston those organisms adapted to living on the underside of a surface

hypotheca see frustule

hypsographic curve (depth-area curve) is a graphic representation of the
relationship between the surface area of a lake and its depth. This
relationship may be expressed in terms of percent of the lake area
which is above water of a given depth, or in absJlute units such as m2,
hectares, or km2. The curve is constructed by plotting depth along
the vertical axis ordinatee) and area along the horizontal axis

Ideal Gas Law see Boyle-Charles' Law

inertial force a term used to designate a force in a given coordinate
system arising from the inertia of a parcel moving with respect to
another coordinate system. For example, the Coriolis acceleration
of a parcel moving with respect to a coordinate system fixed in
space becomes an inertial force, the Coriolis force, in a coordinate
system rotating within the earth

influent flowing in or into

infrared (IR) electromagnetic radiation having wavelengths greater than
those of visible red light and shorter than those of microwaves
(radar). The range is fron 0.76 microns (760 nm) to 990.6 microns

in situ in the original location

interflow condition in which an incoming flow of water to a lake has
a greater density than that of the epilimnion but less than that
of the metalimnion or hypolimnion of the lake it is flowing into,
so that it enters as a plume at an intermediate depth

internode a section of a plant lying between two seccessive nodes

inverse stratification winter phenomenon of temperate lakes in which
colder water lays over warmer water

in vitro by derivation, means "in glass". In general it is applied
to biological processes when they are experimentally made to occur
in isolation from the whole organism

ion an atom or molecularly bound group of atoms which has gained or
lost one or more electrons and therefore has a negative or positive

ionization potential energy required to remove electrons from the molecule

isogamy condition in which gametes are similar, and not differentiated
in respect to sexuality

isopleth a line of equal or constant value of a given quantity with
respect to either space or time

isothermal having constant temperature

isotope one of two or more atoms, the nuclei of which have the same
number of protons but different numbers of neutrons

karst a topography formed over limestone, dolomite or gypsum and
characterized by sinkholes, caves, and underground drainage

Kelvin waves are waves found in large lakes that are described by
mathematical models in which geostrophic effects are taken into
account and wave components decrease in amplitude as they move
away from the shoreline

kettle lakes lakes formed by the melting of isolated blocks of ice
left behind in glacial till as glaciers retreated

Kranz anatomy in German Kranz means "halo" or "wreath" and that is
the appearance of the concentric arrangement of thick-walled
photosynthetic cells surrounding the vascular bundles in the
leaves of most C-4 plants

lacustrine of or pertaining to a lake

lamellar layered

laminar flow nonturbulent flow of a liquid in layers near a boundary;
organized unidirectional movement of a liquid or a gas. Streamline
flow of an incompressible, viscous fluid; all particles of the
fluid move in distinct and separate lines

langley (ly) equals 1 cal cm2

Langmuir circulation water movement induced by turbulent transport
organized into vertical helical currents in the upper layers of
a lake

latent heat of evaporation the quantity of energy required to evaporate
1 mole, or unit mass, of a liquid, at constant temperature and

latent heat of fusion the increase in enthalpy accompanying the conversion
of 1 mole, or unit mass, of a solid to a liquid at its melting point at
constant temperature and pressure

leeward situated away from the wind

lentic standing bodies of water

Liebig's "Law of the Minimum" under "steady state" conditions the growth
and reproduction of an organism will be limited by the abundance of
the substance that, in relation to the needs of the organism, is least
available in the environment

light the visible portion of the electromagnetic spectrum (380 to 780 nm)

lignin an organic, complex aromatic compound that provides strength and
rigidity to tissues in which it occurs

limnology the study of freshwaters and the functional relationships and
productivity of their communities and how they are affected by the
dynamics of physical, chemical, and biotic environmental parameters

Lineweaver-Burkequation the reciprocal of the Michaelis equation expressed
as a formula for a straight line (y = mx + b), that is:
1 Km 1 1
Vo Vmax [S V

This straight line, "double reciprocal" plot is preferred to the
hyperbolic plot of the Michaelis equation as a means of determining
Vmax and Km, since a straight line is more accurately drawn and
extrapolated than a curve

littoral region interface zone between the land of the drainage basin
and the open water of the lake in which macrophytes grow or potentially
could grow

long waves waves in which the wavelength is long in comparison to and
much greater than the amplitude. They are non-dispersive and
travel at a speed independent of wavelength

lotic flowing waters, e.g.-streams

lunar tide the portion of a tide produced by the gravitational forces of
the moon

lysis destruction of cells through damage to or rupture of the plasma

maars volcanic craters created by violent explosion but not accompanied
by igneous extrusion; frequently they are filled with water creating
small circular lakes

macrophyte a large plant; typically, one that is visible to the naked eye

marl calcium carbonate (CaCO3); actually, a deposit of crumbling earthy
material composed principally of clay with magnesium and calcium
carbonate; used as a fertilizer for lime deficient soils

maximum depth (zm) the greatest depth of the lake

maximum length (1) distance of the lake surface between the most distant
points on the lake shore

maximum width or breadth (b) maximum distance on the lake surface at
a right angle to the line of maximum length between the shores
mean depth (z) the volume divided by its surface area: 2 = A
mean width (5) is equal to the area divided by the maximum length: b = 1

meromictic lakes those lakes that have only a partial mixing, the primary
upper layers do not mix with the lower portion

meroplanktonic composite of intermittently occurring species in the

mesotrophic a water body that is moderately supplied with nutrients and
has moderate production in terms of organic matter being fixed; it
is intermediate to eutrophic and oligotrophic waters (Gr.-mesos=middle,
trophein=to nourish)

metalimnion the layer of water in a lake between the epilimnion and
hypolimnion in which the temperature exhibits the greatest difference
in a vertical direction. Words that are synonomous are sprunschicht
(German), and discontinuity layer; thermocline is not really synonomous
(Gr.-meta=between, limne=lake)

mho a unit of conductance, equal to the conductance between two points of
a conductor such that a potential difference of 1 volt between these
points produces a current of 1 amp; the conductance in mhos is the
reciprocal of its resistance in ohms; also known as siemans

Michaelis equation if one experimentally measures the initial velocity (vo)
of a simple reaction in which a substrate (S) is being converted to some
product (P) when it is being catalyzed by a given concentration of enzyme
[eo] under constant reaction conditions, one finds that vo varies with
the concentration of the supplied substrate [S]. Plotting vo versus [S]
results in a rectangular hyperbolic curve which means the relationship
between these two entities must be definable in terms of the equation of
a rectangular hyperbole. The experimentally derived equation which
relates vo and [S] is normally written as:

V [S]
0o [S + K,

and is known as the Michaelis equation. It should be noted that this
makes no assumptions concerning the mechanism of the enzymatic reaction;
it merely describes how vo is observed to vary with [S], in regard to the
two experimentally derived constants Vmax and Km. These constants (or
kinetic parameters) are defined as follows:

V is the maximum value of vo which occurs at high concentrations
of substrate; that is, Vmx is independent of [S] so long as
it is saturating. It is measured in units of quantity of
substrate transformed per unit time for a given quantity of

Km (called the Michaelis constant) can only be derived experimentally
and equals the substrate concentration [S] at which the reaction
is proceeding at half its maximum velocity; that is, vo = iVmax.
Values for Km are expressed in units of concentration

Michaelis-Menten equation is written as:

v CW !
Vmax [S]
o [S] + Ks

which has the same form as the experimental Michaelis equation but differs
in that it attempts to explain the significance of Vmax and Km in terms of
the mechanism of an enzyme catalyzed reaction. It is based on a two-step
mechanism in which there is an initial combination of enzyme (E) with its
substrate (S), to form an enzyme-substrate complex (ES), a reversible pro-
cess, which in turn results in the enzyme being regenerated and a product
(P) being formed in an irreversible process. This can be exp.-ssed in the
following manner:
E + S <== ES -> E + P

In the Michaelis-Menten equation, Ks is the dissociation constant for the
enzyme-substrate complex going back to the enzyme and substrate

microcrustacea microscopically small crustaceans

microeinstein (uE) 10-6 Einsteins or 6.02 x 1017 quanta

micrometer (um) a micron

micron unit of length that is equal to 10-6 m

millimicrons unit of length equal to a nanometer

miscible liquids that are mutually soluble (L.-miscere=to mix)

mixolimnion the upper stratum of water which periodically circulates
in meromictic lakes

mixotrophic an organism capable of assimilating its own organic
constituents from inorganic precursors but also requiring external
sources of organic compounds

monimolimnion the deeper stratum of water that is perennially stagnant
in meromictic lakes

monoecious gametes are derived from the same individual

monomictic lakes, cold lakes with water temperatures never greater than 4C
and with only one period of circulation in the summer at or below 4C

monomictic lakes, warm in these lakes temperatures do not drop below 4C,
they circulate freely in the winter at or above 40C and they stratify
directly in the summer

moraine an accumulation of glacial drift (till) deposited by direct glacial

morphology structure and form of an organism

mucilaginous characterized by having a sticky organic substance made of
polysaccharides that form chemical bonds with water

nanometer (nm) unit of length that is equal to 10-9 m

nannoplankton organisms of small size suspended in the open water which
cannot be collected by net..; see plankton sizes (Gr.-nannos=dwarf)

net productivity the gross rate of production of organic matter less
losses, divided by the time interval

neuston the microscopic component of the pleuston; divided into the
epineuston (living on the upper surface) and the hyponeuston (living
on the under surface)

niche a multi-defined term that includes the physical space occupied by
an organism and also its functional role in the community

node, or nodal region that area of a plant from which lateral organs or
branches develop; a multicellular area which bears sex organs

nomogram (nomograph) a chart of an equation containing three variables by
means of three scales. A straight line cuts the three scales in values
of the three variables satisfying the equation

03 ozone, an allotropic form of oxygen, containing three atoms in the mole-
cule; having a characteristic odor a little like chlorine; a powerful
oxidizing agent

obligate absolutely, indispensable; essential; compare facultative

oligomictic lakes lakes with few mixings, generally tropical lakes that
have rare periods of circulation at irregular intervals and temperatures
always well above 4C

oligotrophic waters low in nutrients with low organic production (Gr.-oligos=
small, trophein=to nourish)

oogamy sexual reproduction in which a large, non-motile female gamete (egg)
is fertilized by a small, flagellated male gamete antherozoidd)

open lake a lake that has an outflow

optical density see absorbance

orthograde a stratification curve for temperature or a chemical factor in a
body of water which has a straight uniform course (Gr.-orthos=straight)

osmosis the spontaneous movement of a solvent from one region in a solution
where its activity is higi, to another region where its activity is low,
the regions being separated by a semi-permeable membrane

osmotic pressure the pressure which must be exerted on a solution to prevent
any net movement of solvent between the solution and its pure solvent
when they are separated by a semi-permeable membrane

overflow a term describing the condition in which an incoming flow of water
to a lake has a lesser density than that of the lake it is flowing into
and thus flows over the top of the lake water

oxbow lake a crescent-shaped, relatively shallow lake formed under certain
conditions by a meandering river

oxygen deficit the difference in the amount of oxygen present at the begin-
ning and at the end of stratification below a given depth

oxygen deficit, absolute difference between the.observed oxygen concentration
and the saturation value at 40C at the pressure of the lake surface

oxygen deficit, actual difference between the oxygen content observed at any
point and the saturation value of that same quantity of water at its
observed temperature at the pressure of the lake surface

oxygen deficit, relative difference between the oxygen content of the
hypolimnion and that empirically determined at the end of spring turnover

PAR or PhAR, see photosynthetically active radiation

parthenogenesis development of an egg into a new individual without being
fertilized. Eggs which develop in this way are usually diploid so all
offspring are genetically identical to the parent

partial (or temporary) meromixis is when a normally dimictic lake skips a
period of circulation, usually the spring one

partial pressure the pressure that would be exerted by one component of a
mixture of gases if it were present alone in a container; see Dalton's
Law of Partial Pressures

particulate matter matter in the form of small liquid or solid particles

paternoster lakes a chain of small lakes in a glaciated valley resembling
a string of beads

peat a dark-brown or black material produced by the partial decomposition
and disintegration of mosses, sedges, trees, and other plants that grow
in marshes and other wet places

pectin complex colloidal substances of high molecular weight found in cell
walls of unlignified tissue

pelagic the region of open waters in seas and inland lakes

pennate diatoms (Pennales) a grouping of diatoms that exhibit bilateral
morphology, meaning their shape is such that it is capable of being
halved in one and only one plane in such a way that the two halves are
approximately mirror-images of each other

perennation of plants, survival from year to year by vegetative means

periphyton the community of organisms that are sessile or attached to
any submerged substrate; compare aufwuchs

perturbation state or condition of being disturbed or agitated

phaeopigment degradation products of plant pigments

phagotrophic able to ingest solid particles

photic zone surface zone of a body of water sufficiently illuminated for
photosynthesis, also called the euphotic zone

photoassimilates compounds resulting from photosynthesis

photoautotrophic of an organism, independent of outside sources of organic
substances for provision of its own organic constituents, which it can
manufacture from inorganic material using energy that is derived from

photoheterotrophic of an organism, that requires an external source of
organic substances and derives the energy for transformations of
these compounds from sunlight

photon see quantum

photophosphorylation coupling of phosphate with ADP to make ATP (which is
a phosphorylation process) using light energy absorbed in photosynthesis

photorespiration type of respiration characteristic of certain plant species
that is activated by light. Biochemically different from normal respira-
tion since in this process CO2 is generated as a result of glycolic acid,
a direct product of the Calvin cycle. Plants displaying photorespiration
have higher CO2 compensation points and photosynthetically are less
efficient than those which do not; these two types of plants also differ in
other significant and apparently interrelated aspects. Besides the
biochemical differences they also display anatomical differences

photosynthesis conversion of incident light to chemical energy through the
synthesis of organic matter (carbohydrates) from C02 and water, with
the simultaneous release of oxygen. The incident light is converted
into chemically useful energy at two kinds of reaction centers. One of
them is called Photosystem I, it generates reducing power in the form of
NADPH, whereas the other, Photosystem II, splits water to produce 02 and
generates a reductant

photosynthetic efficiency is the ratio of the caloric equivalent of integral
(entire) photosynthesis to the caloric value of the radiation inputs;
values range from less than 0.01 to about 3 percent

photosynthetically active radiation (PAR, or PhAR) that region of the
electromagnetic spectrum between 400 to 700 nm.

phototactic the movement of an organism in response to a source of light

phototrophic of organisms obtaining energy from thV radiation of the sun

phycobilin red phycoerythrinn) and blue phycocyaninn) protein-bound pigments
which are open-chained tetrapyrroles and occur in some groups of algae;
see biliproteins

phycocyanin a blue pigmented phycobilin

phycoerythrin a red pigmented phycobilin

phytoplankton small plants that have no or very limited powers of locomotion
and are subject to distribution by water movements

piedmont lying at the foot of a mountain or mountain range

Planck's constant (h) a universal constant relating the energy of a photon
to the frequency of radiant energy that emitted it; its numerical value
is 6.624 x 10- erg-seconds

planimeter an instrument that measures the area of a plane figure as a
mechanically coupled pointer traverses the figure's perimeter

plankton the community of the free water which are passively floating or
weakly motile aquatic plants and animals (Gr.-planktos=wandering)

plankton sizes catergorization of plankton based on their size ranges:

macroplankton greater than 500 im
microplankton Z 50 to 500 um
(net plankton)
nannoplankton 10 to = 50 pm
ultraplankton 0.5 to 10 pm

plasmalemma external plasma membrane in plants

plastids small, variously shaped bodies in cytoplasm of plant cells contain-
ing pigments and/or reserve food materials

platinum units a comparative color scale utilizing a specific mixture of
platinum-cobalt compounds

playas large pans or nearly level areas at the bottom of a desert basin,
sometimes temporarily covered by water

pleuston community of organisms adapted to the interface habitat between
air and water, (i.e. the water's surface)

plunge-pool lakes are lakes formed at the base of a waterfall

polymictic lakes these are lakes with frequent or continuous circulation.
There are cold polymictic lakes, circulating at temperatures near or
slightly above 40C. There are also warm polymictic lakes that exhibit
frequent circulation at temperatures well above 40C.

polymorphism having several different forms

polyphotic adapted to a wide range of light intensities

primary productivity rate at which radiant energy is stored by the photo-
synthetic activity of producer organisms (green plants) in the form of
organic substances

pristine pertaining to, or typical of the primitive or original conditions;

production the weight of new organic material formed over a period of time,
plus any losses during that period due to respiration, excretion,
secretion, injury, death, or grazing

productivity is the rate of production expressed as production divided by
the period of time. It is important to remember that it is a rate
function, an amount of energy fixed in a given amount of time; see
primary productivity, secondary productivity, gross productivity, and
net productivity

progressive wave a wave which transfers energy from one part of a medium
to another, in contrast to a standing wave. Also known as a free-
traveling wave

prokaryotes procaryotess) organisms composed of prokaryotic cells. Where
prokaryotic cells are characterized by having the following features:

1 they are undifferentiated and lack internal membranes which
separate the nucleus from the cytoplasm and which isolate
the enzymatic machinery of photosynthesis and respiration
into specific organelles (that is, no mitochondria, chloro-
plasts, etc. can be distinguished)
2 reproduction is usually by binary fission and nuclear divi-
sion does not occur by mitosis
3 the cell wall contains a specific mucopeptide (protein con-
taining carbohydrates) that acts as a strengthening compo-

compare eukaryotes

pseudoraphe in diatoms, a depression of the cell wall

pyranometer an instrument used to measure the combined intensity of incoming
direct solar radiation and diffuse sky radiation; compares heating
produced Ly the radiation on blackened metal strips with that produced
by an electric current. Also known as a solarimeter

pyrrole C4H5N, a five membered heterocyclic (not all of the same elements
in the ring) compound that is a water insoluble, yellowish oil with a
pungent taste; soluble in alcohol, ether, and dilute acids

quantum (or photon) elementary unit or packet of energy of which light
(electromagnetic radiation) is composed (L.-quantus=how much)

quantum energy (E) the energy (E) of a quantum or photon is equivalent to
the frequency (v) of the radiation times Planck's constant (h):
E = hv

A photon's energy is directly proportional to the frequency of radiation
and higher frequencies have more energetic photons. Since the frequency
is equal to velocity divided by the wavelength (v = c/) then,
E = h(c/x)

Thus, the energy of a photon is inversely proportional to wavelength
and longer wavelengths (lower frequencies) have less energetic photons

quiescent inactive or still; dormant

radiant energy energy in the form of waves or pulsations and is said to
be electromagnetic. Certain concepts and equations describe the wave
nature of radiant energy while others describe the particulate nature
of this energy. The "particles" or "packets" of radiant energy are
termed quanta or photons

radiant energy terms there are two sets of terminology for expressing this
energy. One is in physical terms, called radiometric terminology,
the other is in psychophysical terms, called photometric (or illumination)
terminology which are defined in terms of the sensitivity of the human
eye. The former is the preferred means of expression for the biologist
since most of the radiant energy work has to do with photosynthesis;
plants respond in quite different ways to the electromagnetic spectrum
than does the human eye

Radiometric Terminology



Radiant flux Watts(=joules per sec-
calories per minute
ergs per second

Radiant emittance Watts per square meter
(=joules per second per
square meter)
calories per minute per
square centimeter
ergs per second per
square centimeter


same as above

W(=J sec-1)

cal min-1
erg sec"

W m-2 1
(=J sec-3 m-

cal min-l cm-2

erg sec- cm2

same as above

Defining Statement

Physical entity which
has the capacity to
do work

Radiant energy fall-
ing upon a surface in
an interval of time;
energy per unit time
is power

Radiant flux density
emitted per unit area
of surface

Radiant flux density
received per unit area
of surface

Photometric 'or Illumination) Terminology

Luminous energy

Luminous flux


Note: The lumen does not correspond
to a definite number of watts
except at a specific wavelength

Radiant energy express-
ed as psychophysical

Luminous energy evalu-
ated with respect to
its ability to invoke
a response by the hu-
man eye; has the dimen
sions of power


Radiant energy


Photometric Terminology (continued)



Luminous emittance Lumens per square
lamberts(= 1 Im cm-2)


Lumens per square meter
(= 1 lux)
phot(= 1 Im cm-2)
(= 1 Im ft-2)


Im m-2

Im m-2(= 1 lx)

Defining Statement

Luminous flux density
emitted per unit area
of source

Luminous flux density
received per unit area

fc or ft-c

Radiant energy density is usually measured with a pyrheliometer, radiometer,
or actinometer while luminous energy density is usually measured with a
suitably filtered selenium photocell. The interconversions between the
two systems is difficult and requires the careful calibration of the

Many radiation measures are given in
measurements are given in ft-c. The
and illuminance units depends on the
An approximate conversion factor for
over the 400 to 700 nm range is:

W m-2 or cal min-1 sec-1 while light
relationship between irradiance units
spectral composition being received.
a flat spectral distribution curve

1 W m-2 = 21.9 ft-c

relative depth (Zr) maximum depth as a percentage of the mean diameter:
Zr = A

relative oxygen deficit difference between the oxygen content of the hypo-
limnion and that empirically determined at the end of spring turnover

renewal time the amount of time it takes for the entire water body to be
replaced; turnover time

reservoir a body of water collected and stored in a natural or artificial

Richardson number (Ri) dimensionle i number of fluid mechanics used in
studying the stratified flow of multi-layered systems. Equal to the ac-
celeration of gravity (g) times the density gradient of a fluid (p),
divided by the product of the fluid's density and the square of its
gradient at a wall

ripples waves on a fluid surface of sufficiently short wavelength, less
than 6.28 cm (2 pi), in which the surface tension of that fluid acts
as the restoring force

salinity the quality of being saline; saltiness; ionic composition of an
aqueous solution, in freshwaters it is best expressed as the sum of the
eight major cations and anions (Ca+2, Mg+2, Na+l, K+1, HC03-1, C03-2,
S04-2, and C1-1) in mass or milliequivalents per liter

saturation the condition in which a further increase in some cause produces
no further increase in the resultant effect

scenescence growing old

Secchi disk transparency is the mean depth of the point where a weighted
white disk, 20 cm in diameter, disappers when viewed from the shaded
side of a vessel, and the point where it reappears upon raising it after
it has been lowered beyond visibility

secondary productivity rate at which energy is stored at the consumer levels,
i.e.-herbivores, carnivores, and detritivores

sedentary attached, stationary; sessile or stalked

sediment a mass of organic or inorganic solid fragmented material, or the
solid fragment itself, suspended in, carried by, or dropped by air, water,
or ice

seiche a standing wave (surface or internal) oscillation of an enclosed or
semi-enclosed body of water that continues, pendulum fashion, after the
cessation of the originating force, which may have been atmospheric or
seismic. Perhaps from the French word "seche" which means dry, since
part of the shore is sometimes laid bare by the recession of the water

sequestering agents chemical compounds that inhibit or prevent normal ion
behavior by combining with other materials, especially the prevention of
metallic ion precipitation from solution by the formation of a coordina-
tion complex with a phosphate

serial dilution sequential dilutions of an initially concentrated amount

sessile permanently attached or fixed; not free-moving; sedentary

seston all particulate matter suspended in water (Gr.-sestos-strained)

Shannon-Wiener function is a species diversity index that combines the
number of species with equitability or the evenness of allotment of
individuals among species:

H = (i)'(log2P)

Where: H = information content of sample (bits/individual) = index of
species of diversity
S = number of species
pi= proportion of total sample belonging to ith species

This function was derived independently by Shannon and Wiener and is
sometimes mislabeled the Shannon-Weaver function


shoreline (L) intersection of the land with the water

shoreline development (Dr) the ratio of the length of the shoreline (L) to
the length of the circumference of a circle of area equal to that of the
DL =
D 2 L/TAo

A DL value of one means that the lake has a circular shoreline, the more
it deviates from one the more convoluted the shoreline

shortwaves waves in which the wavelength is less than the water depth. They
are dispersive and travel at speeds proportional to the wavelength raised
to the power (x)

siemens see mhos

siliceous containing or consisting of silica (Si02)

soft waters waters containing low concentrations of ionic species and are
usually derived from drainage of acidic igneous rocks. Usually taken as
being less than 50 mg CaCO3 L-1 total hardness

solar constant the amount of direct solar radiation per unit of time from
the sun, incident upon a surface just outside the earth's atmosphere
perpendicular (normal) to the rays of the sun at the earth's mean
distance from the sun

solution lakes lake basins formed by the dissolution of the bedrock materials

specific heat that amount of heat in calories that is required to raise
the temperature 1C of a unit weight of a substance

specific gravity the ratio of the density of a substance to the density of

stability per unit area of a lake (S) is the quantity of work or mechanical
energy in ergs required to mix the entire volume of water to uniform
temperature by the wind, without the addition or subtraction of heat

standing crop weight of -rganic material that can be sampled or harvested
by normal methods at any one time from a given area

standing waves disturbances that are not progressive. Standing waves result
from the superposition of two waves traveling in opposite directions,
having identical amplitudes and frequencies. The wave disturbance is
maximal at certain points occurring periodically, called loops or anti-
nodes, and it is zero at points between them, called nodes

steno having a narrow range (Gr.-stenos=narrow)

Stoke's Law is the relationship applicable to the motion of a small spherical
body in a fluid under gravitational attraction; the body attains a constant
velocity (V), equal to:

V = 2gr2(Ps-PF)

Where: g = the acceleration due to gravity; = 980.665 cm sec"2
r = the radius of the sphere
PS= the density of the sphere
PF= the density of the fluid
n = the viscosity of the fluid

stratification horizontal layering of waters of differing densities;
usually the density differences are produced in a lake as the result of
temperature changes at various depths

summer kill a catastrophic event that occurs under certain conditions
(usually late summer in a shallow eutrophic lake) in which the
oxygen content is severely reduced to almost complete anoxia and
there are massive die-offs of many species of fauna

supersaturation the condition of containing an excess of some material over
the amount required for saturation

surface waves are waves of distortion on the free-surface separating two
fluid phases, usually a liquid and a gas or vapor of low density. The
waves are classified as gravitational waves or ripples, depending on
whether gravity or surface tension is the controlling force in their

symbiotic the association of dissimilar organisms to their mutual advantage

tectonic pertaining to, causing or resulting from the structural deformation
in the earth's crust

temperate pertaining to the geographic region which lies between the latitudes
23.5* and 66.5*

thallus a plant body wh.cn is not differer+~ated into true roots, stems,
or leaves

thermal bar a narrow transitional zone between the open water mass and
littoral stratified water in which the water is nearly a vertical 4C

thermocline is the plane or surface of maximum rate of decrease of
temperature with respect to depth

Thermodynamics, First Law of states that the total energy of an isolated
system is constant, that is, it can neither be created or destroyed
but it can be transformed from one type into another

Thermodynamics, Second Law of states that in a closed system the only
reactions that can occur spontaneously are those that increase the
total entropy (a measure of disorder) of the system and its surroundings

thermokarst lakes Arctic lakes formed by the coalescing of small cryogenic
lakes into a larger pond

thermophilic requiring high temperatures for normal development with
optimum growth temperatures being above 45C

transmittance (T) is the fraction of light transmitted by a substance
expressed as decimal fraction:


Where: I = intensity of transmitted radiant energy
I = intensity of incident radiant energy

transparent having the property of transmitting light without appreciable
scattering so that bodies lying beyond are entirely visible

transpiration the evaporation of water from plants

trichome is the basic structural unit of a filamentous blue-green alga
consisting of a linear row of cells, minus a mucilaginous sheath

trophogenic zone superficial stratum of a lake in which photosynthetic
production occurs, it is when organic products are made from mineral
substances on the basis of light energy

tropholytic zone aphotic deep stratum of a lake where heterotrophic
decomposition of organic matter takes place

turbidity is a condition in which sediment or other particulate matter
is stirred-up or suspended in the water column, giving it a muddied
or cloudy appearance

turbulent flow motion of fluids in which local velocities and pressures
fluctuate irre>,larly, in a random manner

turgor pressure pressure exerted against the cell wall by its internal
contents swelling the cell

turnover.- circulation of a water body; usually in reference to temperate

ultraviolet (UV) range of electromagnetic radiation extending from about
4000 angstroms (400 nm), just beyond the violet in the visible portion
of the spectrum, to about 40 angstroms (4 nm), on the border of the
x-ray region

imhos micro-mhos, 10-6 mho

valve in diatoms, one half of the wall of the cell; two together constitute
the entire cell wall which is called the frustule

vapor pressure (or saturation vapor pressure) of a substance (solid or
liquid) is the pressure exerted by its vapor when in equilibrium with
the substance; for pure substances it depends only on the temperature

variegated having streaks, marks or patches; distinguished or characterized
by variety; diversified

vernal pertaining to spring

viscosity internal friction of a fluid, that is, the force between particles
in the fluid which causes a resistance to flow; a property of fluids is
a shearing stress which gives the coefficient of viscosity of a particular
fluid when divided by the rate of shear; the poise is a metric unit of
viscosity; viscosity varies inversely with temperature

volatile evaporating readily at normal temperatures and pressures; capable
of being readily vaporized

volume (V) the volume of the lake basin is the integral of the areas of
each stratum at successive depths from the surface to the point of
maximum depth

vortex any flow possessing a rotary motion

vortical motion motion of a fluid (as at the boundary layer between two
layers flowing in opposite directions) in which each individual
particle rotates about its own axis. Also called rotational motion

wave a disturbance which propagates from one point in a medium to other
points without giving the medium as a whole any permanent displacement

wavelength (x) the distance between waves or crpets of energy in electro-
magnetic radiation. The wavelength is equal -o the velocity divided by
the frequency:

Where: c = 2.998 x 1010 cm sec-1 (the speed of light)
v = frequency (sec-l)

wave number (v' or k) a term that is convenient in some applications and
equal to the reciprocal of the wavelength which is measured in centi-

wet weight see fresh weight

wind factor ratio of water velocity of surface currents to wind velocity

Winkler titration a chemical method for estimating dissolved oxygen in
water. Manganous hydroxide is added to the sample and reacts with
oxygen (if present) to produce a manganese compound which in the
presence of acid potassium iodide, liberates an equivalent quantity
of iodine that can be titrated with a standard solution (usually
sodium thiosulfate)

winter kill massive die-offs of many species of fauna in a body of water
due to conditions of low oxygen content or anoxia during the winter

xanthophyll see carotenoid

yield is the crop expressed as a rate

zooplankton the animal portion of the plankton (Gr.-zoion=animal)

zygote a diploid cell resulting from a union of sex cells; a fertilized egg

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