ENVIRONMENTAL HEALTH SERIES
Division of Water Supply
and Pollution Control
GLOSSARY
of Commonly Used
BIOLOGICAL
and RELATED TERMS
in Water and Waste
Water Control
U.S. DEPARTMENT OF HEALTH
EDUCATION, AND WELFARE
Public Health Service
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Glossary Of Commonly Used
Biological And Related Terms In
Water And Waste Water Control
Jack R. Geckler
Kenneth M. Mackenthun
William Marcus Ingram
Technical Services Branch
Robert A. Taft Sanitary Engineering Center
U. S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE
Public Health Service
Division of Water Supply and Pollution Control
Cincinnati 26, Ohio
July 1963
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The ENVIRONMENTAL HEALTH SERIES of reports was estab-
lished to report the results of scientific and engineering studies
of man's environment The community, whether urban, subur-
ban, or rural, where he lives, works, and plays, the air, water,
and earth he uses and re-uses, and the wastes he produces and
must dispose of in a way that preserves these natural resources
This SERIES of reports provides for professional users a central
source of information on the intramural research activities of
Divisions and Centers within the Public Health Service, and on
their cooperative activities with State and local agencies, re-
search institutions, and industrial organizations The general
subject area of each report is indicated by the two letters that
appear in the publication number, the indicators are
AP - Air Pollution
AH - Arctic Health
EE - Environmental Engineering
FP - Food Protection
OH - Occupational Health
RH - Radiological Health
WP - Water Supply and
Pollution Control
Triplicate tear-out abstract cards are provided with reports in
the SERIES to facilitate information retrieval Space is provided
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Reports in the SERIES will be distributed to requesters, as sup-
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tified on the title page or to the Publications Office, Robert A
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Public Health Service Publication No. 999-WP-Z
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Preface
The extensive use of biologists in water supply, sewage
treatment, waste water control, and water quality surveys of
streams, lakes, and estuaries is of relatively recent origin.
As a result, bilological terminology is often unfamiliar to
many who could benefit from a more comprehensive apprecia-
tion of the investigations and possible uses of biological data.
The need for better understanding of biological terms that
can be usefully applied in engineering reports of environmental
investigations of water has existed for a number of years.
These terms are used m introductory and advanced courses for
water pollution control engineers, chemists, administrators,
waterworks operators, and sewage treatment plant operators.
In the GLOSSARY OF COMMONLY USED BIOLOGICAL AND
RELATED TERMS IN WATER AND WASTE WATER CONTROL,
we have endeavored to fulfill this need. This glossary contains
selected terms defined so that those persons not intimately
acquainted with the biological field will have a more precise
understanding of them. Its purpose is to serve as an intro-
duction to the aquatic biologist's technical terminology. Dili-
gent use should foster a deeper appreciation of the science,
permit a better understanding of many technical reports and
papers, and promote the further cooperation that is so necessary
among the associated disciplines of water pollution control.
THE AUTHORS
111
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Glossary
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LICHT
SOURCE
Plate I. Lake Zones and Regions.
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Glossary Of Commonly Used
Biological And Related Terms In
Water And Waste Water Control
ACCLIMATION - The process of adjusting to a change in an en-
vironment.
ADAPTATION - A change in the structure, form, or habit of an
organism resulting from a change m its environment.
AEROBIC ORGANISM - An organism that thrives m the presence
of oxygen.
ALGAE (Alga) - Simple plants, many microscopic, containing
chlorophyll. Most algae are aqjatic and may produce a nuisance
when conditions are suitable for prolific growth.
ALGICIDE - A specific chemical highly toxic to algae. Algicides
are often applied to water to control nuisance algal blooms.
ALGOLOGY - The study of algae
AMPHIBIOUS ORGANISM - An organism adapted for life on land
or in water.
AMPHIPODS (See Scuds. )
ANADROMOUS FISHES - Fishes that spend a part of their life
in the sea or lakes, but ascend rivers at more or less regular
intervals to spawn. Examples are sturgeon, shad, salmon,
trout, and striped bass.
ANAEROBIC ORGANISM - An organism that thrives in the ab-
sence of oxygen.
1
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ANNELIDS
ANNELIDS - Segmented worms, as distinguished from the non-
segmented roundworms and flatworms. Most are marine, how-
ever, many live m soil or fresh water. Aquatic forms may es-
tablish dense populations in the presence of rich organic de-
posits. Common examples of segmented worms are earthworms,
sludgeworms, sandworms, and leeches.
ASSIMILATION - The transformation of absorbed nutrients into
body substances.
AUTOTROPHIC ORGANISM - An organism capable of construc-
ting organic matter from inorganic substances.
BENTHIC REGION - The bottom of a body of water. This region
supports the benthos, a type of life that not only lives upon but
contributes to the character of the bottom. (See Plate I. )
BENTHOS - Aquatic bottom-dwelling organisms. These include
(1) sessile animals, such as the sponges, barnacles, mussels,
oysters, some of the worms, and many attached algae, (2) creep-
ing forms, such as insects, snails, and certain clams, and
(3) burrowing forms, which include most clams and worms.
BIO-ASSAY - A determination of the concentration of a given
material by comparison with a standard preparation, or the de-
termination of the quantity necessary to affect a test animal un-
der stated laboratory conditions.
BIOMASS - The weight of all life in a specified unit of environ-
ment or an expression of the total mass or weight of a given
population, both plant and animal.
X2
AQUATIC SOW BUGS (Isopoda) -
Macroscopic aquatic crustaceans
that are flat from top to bottom.
Most are marine and estuarine.
They are scavengers that live
secretively under rocks and
among vegetation and debris.
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BLUE-GREEN ALGAE
BIOTA - All living organisms of a region.
BIVALVE - An animal with a hinged two-valve shell, examples
are the clam and oyster.
BLACK FLY LARVAE (Simulu-
dae) - Aquatic larvae that produce
a silk-like thread with which they
anchor themselves to objects in
swiftrunning waters. With a
pair of fan-shaped structures,
a larva of this type produces
a current of water toward its
mouth and from this water in-
gests smaller organisms. The
adults are terrestrial; females
feed on the blood of higher ani-
mals.
BLOODWORMS (Tendipedidae =
Chironomidae) - Cylindrical
elongated midge larvae with pairs
of prolegs on both the first thoracic
and last abdominal segments. Al-
though many species are blood-red
in color, some are pale yellowish,
yellowish red, brownish, pale
greenish yellow, and green. Most
feed on diatoms, algae, tissues
of aquatic plants, decaying or-
ganic matter, and plankton.
Some are associated with rich or-
ganic deposits. Midge larvae are
important as food for fishes.
BLOOM - A readily visible concentrated growth or aggregation
of plankton (plant and animal).
BLUE-GREEN ALGAE - A group of algae with a blue pigment,
in addition to the green chlorophyll. A stench is often asso-
ciated with the decomposition of dense blooms of blue-green
algae m fertile lakes.
3
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CADDISFLY LARVAE
CADDISFLY LARVAE (Tri-
choptera) - Aquatic larvae
found in a variety of habitats.
Many build cases of small rocks,
shells, wood, and plants and
feed upon plant tissue and small
animals captured m nets they
place near the case entrance.
Adults have well-developed
X2. 2
wings but no functional mouth
parts. Eggs are deposited on
sticks or stones m water.
CATADROMOUS FISHES - Fishes that feed and grow in fresh
water, but return to the sea to spawn. The best-known ex-
ample is the American eel.
CHARA - A family of algae possessing cylindrical whorled
branches. The plants grow only m hard water, from the bottom,
and usually have a coating of lime that can be felt between the
fingers. Chara should not be confused with submerged higher
aquatic plants.
CHIRONOMIDAE (See Bloodworms. )
CHLOROPHYLL - The green coloring matter m plants, partly
responsible for photosynthesis.
CLEAN WATER ASSOCIATION - An association of organisms,
usually characterized by many_different kinds (species). These
associations occur m natural unpolluted environments. Because
of competition, predation, etc. , however, relatively few indi-
viduals represent any particular species.
CENTRARCHIDAE (See Sunfish. )
CERCARIA - The tailed, lmma-
ture stage of a parasitic flatworm.
XI 70
4
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DAPHNIA
COARSE OR ROUGH FISH - Those species of fish considered
to be of poor fighting quality when taken on tackle, and of poor
food quality. These fish may be undesirable in a given situation,
but at times may be classified differently, depending upon their
usefulness. Examples include carp, goldfish, gar, sucker,
bowfin, gizzard shad, goldeneye, mooneye, and certain kinds
of catfish.
COELENTERATE - A group of aquatic animals that have gela-
tinous bodies, tentacles, and stinging cells. These animals
occur in great variety and abundance m the sea and are repre-
sented in fresh water by a few types. Examples are hydra,
corals, sea-anemones, and jellyfish.
COLD-BLOODED ANIMALS (Poikilothermic Animals) - Animals
that lack a temperature-regulating mechanism that offsets ex-
ternal temperature changes. Their temperature fluctuates to
a large degree with that of their environment. Examples are
fish, shellfish, and aquatic insects.
CONSUMERS - Organisms that consume solid particles of or-
ganic food material. Protozoa are consumers.
CORYDALIDAE (See Hellgrammites. )
CRUSTACEA - Mostly aquatic animals with rigid outer cover-
ings, jointed appendages, and gills. Examples are crayfish,
crabs, barnacles, water fleas, and sow bugs.
DAMSELFLY NYMPH (Odonata) -
The immature damselfly. This
aquatic insect nymph has an enor-
mous grasping lower jaw and three
flat leaf-like gill plates that pro-
ject from the posterior end of the
abdomen. Nymphs live most of
their lives searching for food
among submerged plants in still
water, a few cling to plants near
the current's edge, and a very few
cling to rocks in flowing water.
The carnivorous adults capture
lesser insects on the wing.
DAPHNIA (See Water Fleas. )
5
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DERMATITIS
DERMATITIS - Any inflammation c± the skin. One type may be
caused by the penetration beneath the skin of a cercaria found
in water, this form of dermatitis is cjmmonly called "swimmers'
itch. "
XI
DRAGONFLY NYMPH (Odonata) -
The immature dragonfly. This
aquatic insect nymph has gills on
the inner walls of its rectal res-
piratory chamber. It has an
enormous grasping lower jaw
that it can extend forward to a
distance several times the
length of its head. Although
many of these nymphs climb
among aquatic plants, most
sprawl in the mud where they
lie in ambush to await their prey.
The carnivorous adults capture
lesser insects on the wing.
DUCKWEED - a free-floating
aquatic flowering plant posses-
sing fronds resembling tiny
green leaves. Small roots be-
neath the leaves easily distin-
guish this plant from algae.
DYSTROPHIC LAKES - Brown-water lakes with a very low lime
content and a very high humus content. These lakes often lack
nutrients.
ECOLOGY - The science of the interrelations between living
organisms and their environment.
6
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EUTROPHI CATION
EKMAN DREDGE - The stan-
dard spring-loaded bottom sam-
pler used for sampling soft
bottoms. The body of the dredge
consists of a square box of sheet
brass (6 by 6, 9 by 9, or 12 by
12 inches). The lower opening
of this box is closed by a pair
of strong brass jaws that snap
shut when the springs are re-
leased. When the jaws are
fully pulled apart, the bottom of
the dredge is open.
EMERGENT AQUATIC PLANTS - Plants that are rooted at the
bottom but project above the water surface. Examples are
cattails and bulrushes.
ENTOMOLOGIST - A specialist m the study of insects.
ENVIRONMENT - The sum of all external influences and condi-
tions affecting the life and the development of an organism.
EPHEMERIDAE (See Mayfly Naiads. )
EPILIMNION - That region of a body of water that extends from
the surface to the thermocline and does not have a permanent
temperature stratification. (See Plate I. )
ERISTALIS (See Rat-Tailed Maggot. )
ESTUARY - Commonly an arm of the sea at the lower end of a
river. Estuaries are often enclosed by land except at channel
entrance points.
EULITTORAL ZONE - The shore zone of a body of water be-
tween the limits of water-level fluctuation. (See Plate I. )
EUPHOTIC ZONE - The lighted region that extends vertically
from the water surface to the level at which photosynthesis
fails to occur because of ineffective light penetration.
EURYTOPIC ORGANISMS - Organisms with a wide range of
tolerance to a particular environmental factor. Examples
are sludgeworms and bloodworms.
EUTROPHICATION - The intentional or unintentional enrich-
ment of water.
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EUTROPHIC WATERS
EUTROPHIC WATERS - Waters with a good supply of nutrients.
These waters may support rich organic productions, such as
algal blooms.
FACULTATIVE AEROBE - An organism that although funda-
mentally an anaerobe can grow in the presence of free oxygen.
FACULTATIVE ANAEROBE - An organism that although funda-
mentally an aerobe can grow in the absence of free oxygen.
FALL OVERTURN - A physical phenomenon that may take place
in a body of water during the early autumn. The sequence of
events leading to fall overturn include (1) cooling of surface
waters, (2) density change in surface waters producing convec-
tion currents from top to bottom, (3) circulation of the total
water volume by wind action, and (4) vertical temperature
equality, 4°C. The overturn results in a uniformity of the phy-
sical and chemical properties of the water.
FAUNA - The entire animal life of a region.
FLATWORMS (Platyhelminthes) - Nonsegmented worms, flat-
tened from top to bottom. In all but a few of the flatworms com-
plete male and female reproductive systems are present in each
individual. Most flatworms are found m water, moist earth,
or as parasites in plants and animals.
FLOATING AQUATIC PLANTS - Plants that wholly or m part
float on the surface of the water. Examples are water lilies,
water shields, and duckweeds.
FLORA - The entire plant life of a region.
FINGERNAIL CLAMS (Sphaern-
dae) - Small clams, usually less
than one-half inch in diameter,
that give live birth to shelled
young.
X3. 5
8
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GREEN ALGAE
FRY (Sac Fry) - The stage in the
life of a fish between the hatch-
ing of the egg and the absorption
of the yolk sac. From this
stage until they attain a length
of 1 inch the young fish are con-
sidered advanced fry.
X2. 5
FUNGI (Fungus) - Simple or complex organisms without chloro-
phyll. The simpler forms are one-celled; the higher forms have
branched filaments and complicated life cycles. Examples of
fungi are molds, yeasts, and mushrooms.
FUNGICIDE - Substances or a mixture of substances intended to
prevent, destroy, or mitigate any fungi.
GAME FISH - Those species of fish considered to possess
sporting qualities on fishing tackle. These fish may be classi-
fied as undesirable, depending upon their usefulness. Examples
of fresh-water game fish are salmon, trout, grayling, black
bass, muskellunge, walleye, northern pike, and lake trout.
GREEN ALGAE - Algae that have pigments similar m color to
those of higher green plants. Common forms produce algal
mats or floating "moss" in lakes.
fish.
GLOCHIDIUM - The larvae of
fresh-water mussels. These
larvae are temporary parasites
that live on the gills, fins, and
general body surface of many
9
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HELLGRAMMITES
XO. 8
HELLGRAMMITES (Corydalidae) -
Dobsonfly larvae. Full-grown
larvae are 2 to 3 inches m
length; they have a dark-brown
rough-looking skin, large jaws,
and posterior hooks. The
aquatic larval stage lasts 2 to
3 years. They are secretive
and predaceous, living under
rocks and debris m flowing
water. These larvae are consi-
dered one of the finest live baits
by fishermen. Pupation occurs
on shore, under rocks and debris
near the stream edge. The ter-
restrial adults are short lived.
HERBICIDE - Substances or a mixture of substances intended to
control or destroy any vegetation.
HERBIVORE - An organism that feeds on vegetation.
HETEROTROPHIC ORGANISMS - Organisms that are dependent
on organic matter for food.
HIGHER AQUATIC PLANTS - Flowering aquatic plants. (These
are separately categorized herein as Emergent, Floating, and
Submerged Aquatic Plants. )
HIRUDINEA (See Leeches. )
HOLOMICTIC LAKES - Lakes that are completely circulated
to the bottom at time of winter cooling.
HYPOLIMNION - The region of a body of water that extends
from the thermocline to the bottom of the lake and is removed
from surface influence. (See Plate I. )
ICTHYOLOGIST - A specialist in the study of fishes.
INSECTICIDE - Substances or a mixture of substances intended
to prevent, destroy, or repel insects.
INVERTEBRATES - Animals without backbones.
ISOPODA (See Aquatic Sow Bugs. )
10
GPO 0O3-338-2
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LITTORAL ZONE
KEMMERER WATER SAMPLER -
An instrument designed to collect
a known volume of water from a
predetermined depth. The sam-
pler construction essentially con-
sists of a brass cylinder with
closable rubber stoppers on each
end. It is suspended in the water
with a rope; closure is accom-
plished when a brass messenger,
which is sent down the rope,
strikes a tripping device.
LD50 (See Median Lethal Dose.)
LEECHES (Hirudinea) - Segmen-
ted worms, flat from top to bot-
tom, with terminal suckers that
are used for attachment and loco-
motion. Various species may
be parasites, predators, or
scavengers, most are aquatic.
XI
LENITIC OR LENTIC ENVIRONMENT - Standing water and its
various intergrades. Examples of lenitic environments are
lakes, ponds, and swamps.
LIFE CYCLE - The series of stages in the form and mode of
life of an organism, i.e., the stages between successive re-
currences of a certain primary stage such as the spore, fer-
tilized egg, seed, or resting cell.
LIMNETIC ZONE - The open-water region of a lake. This
region supports plankton and fish as the principal plants and
animals. (See Plate I.)
LIMNOLOGY - The study of the physical, chemical, and bio-
logical aspects of inland waters.
LITTORAL ZONE - The shoreward region of a body of water.
(See Plate I. )
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LOTIC ENVIRONMENT
LOTIC ENVIRONMENT - Running waters, such as streams or
rivers.
MACROORGANISMS - Plant, animal, or fungal organisms
MAYFLY NAIADS (Ephemendae) -
The immature mayfly. Paired
gills are attached to the upper
surface of the outer edge of
some or all of the first seven
abdominal segments. The ab-
domen terminates m three,
rarely two, slender tails.
Mouth parts are particularly
suited for raking diatoms and
rasping decaying plant stems.
The terrestrial adults lack func-
tional mouth parts and live only
a few hours.
MEDIAN LETHAL DOSE (LD50) - The dose lethal to 5 0 percent
of a group of test organisms for a specified period. The dose
material may be ingested or injected.
MEDIAN TOLERANCE LIMIT (TLm) - The concentration of the
tested material m a suitable diluent (experimental water) at
which just 50 percent of the test animals are able to survive
for a specified period of exposure.
MEROMICTIC LAKES - Lakes in which dissolved substances
create a gradient of density differences in depth, preventing
complete mixing or circulation of the water.
MICROORGANISM - Any minute organism invisible or barely
visible to the unaided eye.
MINNOWS (Cypnnidae) - The family of fishes including such
forms as shiners, dace, and carp.
MOLLUSCICIDE - Substances or a mixture of substances in-
tended to destroy or control snails. Copper is commonly used.
MOLLUSK (Mollusca) - A large animal group including those
forms popularly called shellfish (but not including crustaceans).
All have a soft unsegmented body protected in most instances
by a calcareous shell. Examples are snails, mussels, clams,
and oysters.
visible to the unaided eye.
X2. 7
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PEARL, BUTTON CLAMS
MOSS - Any bryophytic plant characterized by small, leafy,
often tufted stems bearing sex organs at the tips.
MOTILE - Exhibiting or capable of spontaneous movement.
MUSSEL POISON (See Shellfish Poison. )
MYCOLOGY - The study of fungi.
NEKTON - Swimming organisms able to navigate at will.
NEMATODA - Unsegmented roundworms or threadworms.
Some are free living m soil, fresh water, and salt water,
some are found living m plant tissue, others live in animal tissue
as parasites.
NEUSTON - Organisms resting or swimming on the surface
film of the water.
OCEANOGRAPHY - The study of the physical, chemical,
geological, and biological aspects of the sea.
OCULAR MICROMETER - A scaled glass disc that, fitted on
the diaphragm of a microscope ocular, is used in making
microscopic measurements.
OLIGOTROPHIC WATERS - Waters with a small supply of nu-
trients; thus, they support little organic production.
ORGANIC DETRITUS - The particulate remains of disintegrated
plants and animals.
OXYGEN-DEBT - A phenomenon that occurs m an organism
when available oxygen is inadequate to supply the respiratory
demand. During such a period the metabolic processes result
m the accumulation of breakdown products that are not oxidized
until sufficient oxygen becomes available.
PARASITE - An organism that lives on or in a host organism
from which it obtains nourishment at the expense of the latter
during all or part of its existence.
PEARL BUTTON CLAMS (Umor.i-
dae) - Large fresh-water clams.
The shell has a thick mother-of-
pearl layer. The thick-shelled
members of this family are
utilized in the manufacturing of
buttons.
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PELAGIC ZONE
PELAGIC ZONE - The free-water region of a sea. (Pelagic
refers to the sea, limnetic refers to bodies of fresh water. )
PERIPHYTON - The association of aquatic organisms attached
or clinging to stems and leaves of rooted plants or other sur-
faces projecting above the bottom.
PETERSEN DREDGE - A sturdy
steel or iron dredge widely used
for taking samples from hard
bottoms, such as sand, gravel,
marl, clay, and similar materi-
als. It is so constructed that,
both by its own weight and by the
leverage exerted by its closing
mechanism, it bites its way into
/ f \\ /!s\ hard bottoms deep enough to se-
W / y J cure a satisfactory sample. The
\ / y I / area sampled varies from 0.6 to
na 0- 9 square foot, depending on in-
dividual dredge construction.
PHOTOSYNTHESIS - The process by which simple sugars and
starches are produced from carbon dioxide and water by living
plant cells, with the aid of chlorophyll and in the presence of light.
PHOTOTROPISM - Movement in response to a light gradient,
for example, a movement towards light is positive phototropism.
PHYTOPLANKTON - Plant plankton that live unattached inwater.
PISCICIDE - Substances or a mixture of substances intended to
destroy or control fish populations.
PLANKTON (Plankter) - Organisms of relatively small size,
mostly microscopic, that have either relatively small powers of
locomotion or that drift m the water with waves, currents, and
other water motion.
PLANKTON NET - A cloth net,
usually coneshaped, used to
collect plankton. Plankters
separated from water by means
of a net are generally referred
to as net plankton and repre-
sent only a fraction of the total
population. Silk bolting cloth is
regarded as the best material
for plankton nets.
14
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RAPIDS ZONE
PLATYHELMENTHES (See Flatvorms.)
PLECOPTERA (See Stonefly Nymphs.)
POIKILOTHERMIC ANIMALS (See Cold-Blooded Animals.)
POOL ZONE - The deep-water area of a stream, where the
velocity of current is reduced. The reduced velocity provides
a favorable habitat for plankton. Silt and other loose materials
that settle to the bottom of this zone are favorable for burrowing
forms of benthos.
PORIFERA (See Sponges.)
POTAMOLOGY - The study of the physical, chemical, geologi-
cal, and biological aspects of rivers.
PRODUCERS - Organisms that synthesize their own organic
substance from inorganic substances, for example, plants.
PRODUCTION (Productivity) - A time-rate unit of the total
amount of organisms grown.
PROFUNDAL ZONE - The deep- and bottom-water area beyond
the depth of effective light penetration. All of the lake floor
beneath the hypolimnion. (See Plate I. )
PROTOZOA - Organisms consisting either of a single cell or
of aggregates of cells, each of which performs all the essential
functions in life. They are mostly microscopic in size and large-
ly aquatic.
PROTOZOOLOGIST - A specialist in the study of protozoa.
PSYCHODA (See Sewage Fly Larvae. )
RAPIDS ZONE - The shallow-water area of a stream, where
velocity of current is great enough to keep the bottom clear of
silt and other loose materials, thus providing a firm bottom.
This zone is occupied largely by specialized benthic or penphy-
tic organisms that are firmly attached to or cling to a firm
substrate.
15
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RAT-TAILED MAGGOT
ly /I
X2. 3
RAT-TAILED MAGGOT (Tubi-
fera = Eristalis) - An aquatic
fly maggot usually found in foul,
often septic, water. It possesses
a three-segmented, telescopic
air tube that extends through the
water surface, enabling the
maggot to breathe from the at-
mosphere. The larvae live on
decayed organic material.
REDD - A type of fish-spawning area associated with running
water and clean gravel. Fish moving upstream sequentially dig
a pocket, deposit and fertilize eggs, and then cover the spawn
with gravel from the next upstream pocket. Fishes that utilize
this type of spawning area include some trouts, salmons, and
minnows.
RED TIDE - A visible red-to-orange coloration of an area of
the sea caused by the presence of a bloom of certain "armored"
flagellates.
REDUCERS - Organisms that digest food outside the cell wall by
means of enzymes secreted for this purpose. Soluble food is then
absorbed into the cell and reduced to a mineral condition. Ex-
amples are fungi, bacteria, protozoa, and nonpigmented algae.
RHEOTROPISM - Movement m response to the stimulus of a
current gradient m water.
RIFFLE - A section of a stream in which the water is usually
shallower and the current of greater velocity than in the con-
necting pools, a riffle is smaller than a rapid and shallower than
a chute.
ROTIFERS (Rotatoria) - Microscopic aquatic animals, primar-
ily free-living fresh-water forms that occur m a variety of
habitats. Approximately 75 percent of the known species occur
m the littoral zone of lakes and ponds. The more dense pop-
ulations are associated with a substrate of submerged aquatic
vegetation. Most forms ingest fine organic detritus for food,
whereas others are predaceous.
SAC FRY (See Fry. )
16
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SESSILE ORGANISMS
SCAVENGER - An organism that feeds upon decomposing or-
ganic matter.
SCUDS (Amphipods) - Macro-
scopic aquatic crustaceans that
are laterally compressed. Most
are marine and estuarme.
Dense populations are associa-
ted with aquatic vegetation.
Great numbers are consumed
by fish.
SECCHI DISK - A device used to
measure visibility depths in
water. The upper surface of a
circular metal plate, 20 centi-
meters in diameter, is divided
into four quadrants and so
painted that two quadrants di-
rectly opposite each other are
black and the intervening ones
white. When suspended to
various depths of water by
means of a graduated line, its
point of disappearance indi-
cates the limit of visibility.
SEDGWICK-RAFTER CONCENTRATION METHOD - A procedure
for the quantitative determination of plankton in water by use of
a special funnel, a certain grade of sand, and bolting-cloth discs.
SEDGWICK-RAFTER COUNTING CELL - A plankton-counting
cell consisting of a brass or glass receptacle 50 by 20 by 1
millimeter sealed to a 1- by 3-inch glass microscope slide. A
rectangular cover glass large enough to cover the whole cell
is required. The cell has a capacity of exactly 1 milliliter.
SEICHE - A form of periodic current system, described as a
standing wave, in which some stratum of the water in a basin
oscillates about one or more nodes.
SESSILE ORGANISMS - Organisms that sit directly on a base
without support, attached or merely resting unattached on a
substrate.
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SESTON
SESTON - The living and nonliving bodies of plants or animals
that float or swim in the water.
SEWAGE FLY LARVAE (Psy-
choda) - A grayish-white,
cylindrical larvae with hardened
dorsal plates on the posterior
segments. Larvae and pupae
usually occur in filter beds of
sewage treatment plants, m
foul water, and in decaying or-
ganic matter. The terrestrial
adults are small, less than 4
millimeters long, and moth-like,
and often are a nuisance in areas
near trickling-filter plants. The
sewage fly has a 2-week life
X14 X8 cycle.
SHELLFISH POISON (Mussel Poison) - A poison present in shell-
fish that have fed upon certain small marine phytoplankters in
which the toxic principles exist. The shellfish concentrates the
poison without harmful effects to itself, but man is poisoned
through consumption of the toxic flesh.
SIMULIIDAE (See Black Fly Larvae.)
X8
X2. 5
18
SLUDGEWORMS (Tubificidae) -
Tolerant, aquatic, segmented
worms that exhibit marked
population increases in streams
and rivers polluted with organic
decomposable wastes.
SNAIL - An organismthat typi-
cally possesses a coiled shell
and crawls on a single muscu-
lar foot. Air-breathing snails,
called pulmonates, do not have
gills but obtain oxygen through
a "lung" or pulmonary cavity.
At variable intervals most pul-
monate snails come to the sur-
face of the water for a fresh
supply of air. Gill-breathing
snails possess an internal gill
through which dissolved oxygen
is removed from the surrounding
water.
GPO 603—33B-3
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STONEFLY NYMPHS
SPECIES (both singular and plural) - a natural population or
group of populations that transmit specific characteristics from
parent to offspring. They are reproductively isolated from other
populations with which they might breed. Populations usually
exhibit a loss of fertility when hyoridizing.
SPHAERIIDAE (See Fingernail Clams.)
SPHAEROTILUS - A slime-producing, nonmotile, sheathed,
filamentous, attached bacterium. Great masses are often
broken from their "holdfasts" by currents and are carried
floating downstream in gelatinous flocks.
SPONGES (Porifera) - One of the sessile animals that fasten
to piers, pilings, shells, rocks, etc. Most live in the sea.
SPORE - The reproductive cell of a protozoan, fungus, alga, or
bryophyte. In bacteria, spores are specialized resting cells.
SPRING OVERTURN - A physical phenomenon that may take
place in a body of water during the early spring. The sequence
of events leading to spring overturn include* (1) melting of ice
cover, (2) warming of surface waters, (3) density change in
surface waters producing convection currents from top to
bottom, (4) circulation of the total water volume by wind action,
and (5) vertical temperature equality, 4°C. The overturn re-
sults in a uniformity of the physical and chemical properties
of the water.
STAGE MICROMETER - A standardized, accurately ruled scale,
mounted on a glass slide. It is used to calibrate a microscope.
STANDING CROP - The biota present in an environment on a
selected date.
STENOTOPIC ORGANISMS - Organisms with a narrow range of
tolerance for a particular environmental factor. Examples are
trout, stonefly nymphs, etc.
STONEFLY NYMPHS (Plecoptera) - Im-
mature stoneflies. The nymphs live ap-
proximately 1 year m the clean, rapidly
moving water required for their develop-
ment. They live under rocks, in cracks
of submerged logs, and in mats of debris.
Most stonefly nymphs are vegetarians;
however, a number are predaceous and
feed upon small insects and other aquatic
invertebrates. The adults live only a few
weeks; they are secretive creatures, rest-
ing on stones and sticks along the banks of
streams.
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SUB LITTORAL ZONE
SUBLITTORAL ZONE - The part of the shore from the lowest
water level to the lower boundary of plant growth. (See Plate I. )
SUBMERGED AQUATIC PLANT - A plant that is continuously
submerged beneath the surface of the water. Examples are the
pondweed and coontail.
SUNFISH (Centrarchidae) - Carnivorous fresh-water fish, all
of which are spring spawners. The females utilize shallow
depressions excavated by the males for nests; later the males
guard the eggs and the young. Like other essentially carnivorous
fish, the young feed first on microscopic organisms and later
on invertebrates and vertebrates. Members of this family are
generally divided into the following groups (1) largemouth and
smallmouth black bass, (2) crappies and the round sunfish,
(3) true sunfish and rock bass, and (4) Sacramento perch of the
Pacific Coast.
SURBER STREAM BOTTOM
SAMPLER - A compact, light-
weight, portable, quantitative
bottom sampler especially
suitable for sampling organ-
isms from the stone or gravel
bottoms of shallow streams
possessing a strong current.
Construction consists of two
square metal frames of equal
size hinged together. One
frame carries a net of extra
heavy bolting cloth, the other,
when m working position, en-
closes the sampling area
(1 square foot). Dislodged
organisms are carried into
the downstream net.
SWIMBLADDER - An internal membranous gas-filled organ of
many fishes. It may function as a hydrostatic or sense organ,
or as part of the respiratory system.
SWIMMERS' ITCH - A rash produced on bathers by a parasitic
flatworm in the cercarial stage of its life cycle. The organism
is killed by the human body as soon as it penetrates the skin,
however, the rash may persist for a period of about 2 weeks.
SYMBIOSIS - Two organisms of different species living together,
one or both of which may benefit and neither is harmed.
20
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WATERFLEAS
SYSTEMATICS - The science of organism classification.
TENDIPEDIDAE (See Bloodworms.)
THERMOCLINE - That layer m a body of water where the tem-
perature difference is greatest per unit of depth. It is the layer
in which the drop in temperature equals or exceeds 1°C (1.8°F)
per meter (39 37 inches). (See Plate I. )
TLm {See Median Tolerance Limit. )
TOLERANT ASSOCIATION - An association of organisms
capable of withstanding adverse conditions within the habitat.
It is usually characterized by a reduction in species (from a
clean water association) and an increase in individuals repre-
senting a particular species.
TRICHOPTERA (See Caddisfly Larvae.)
TROPHOGENIC REGION - The superficial layer of a lake in
which organic production from mineral substances takes place
on the basis of light energy. (See Plate I. )
TROPHOLYTIC REGION - The deep layer of a lake, where
organic dissimilation predominates because of light deficiency.
(See Plate I. )
TUBIFERA (See Rat-Tailed Maggot. )
TUBIFICIDAE (See Sludgeworms. )
UNIONIDAE (See Pearl Button Clams. )
VERTEBRATE - Animals with backbones.
WARM- AND COLD-WATER FISH - Warm-water fish include
black bass, sunfish, catfish, gar, and others, whereas cold-
water fish include salmon and trout, whitefish, miller's thumb,
and blackfish. The temperature factor determining distribu-
tion is set by adaptation of the eggs to warm or cold water.
WATERFLEAS (Daphnia) - Mostly
microscopic swimming crusta-
ceans, often forming a major
portion of the zooplankton popu-
lation. The second antennae are
very large and are used for
swimming.
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21
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WHIPPLE OCULAR MICROMETER
WHIPPLE OCULAR MICROMETER - A glass disc, marked with
squares, that fits into a microscope ocular and is used to deter-
mine microscopic field areas for counting plankton.
ZOOGLEA - Bacteria embedded m a jelly-like matrix formed as
the result of metabolic activities.
ZOOPLANKTON - Protozoa and other animal microorganisms
living unattached in water. These include small Crustacea,
such as daphnia and cyclops.
ACKNOWLE DGMENTS
The writers express appreciation to Dr. Wm. Bridge Cooke,
Basic and Applied Sciences Branch; Messrs. Ralph Porges, John
Fairall, and Richard L. O1 Connell, all of the Technical Ad-
visory and Investigations Section, Division of Water Supply and
Pollution Control; and Mr. Kenneth Cassel, Publications Officer,
Robert A. Taft Sanitary Engineering Center. Grateful acknow-
ledgment is tendered Juanita M. Churchill and Martha Jean
Wilkey who respectively effectively applied themselves skill-
fully in evolving the illustrations and the drafts of manuscripts.
22
OPO 803-338-4
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BIBLIOGRAPHIC J R Geckler, K M Mac-
kenthun, and W M Ingram. Glossary of
commonly used terms in water and waste
water control PHS Publ No 999-WP-2.
1963 22 pp
ABSTRACT This glossary contains selected
terms defined so that those not intimately
acquainted with the biological field will have
a more precise understanding of them Its
purpose is to serve as an introduction to the
aquatic biologist's terminology.
ACCESSION NO.
KEY WORDS
Aquatic biology
Glossary
Water
Water pollution
Terminology
BIBLIOGRAPHIC J R Geckler, K M. Mac-
kenthun, and W. M. Ingram Glossary of
commonly used terms in water and waste
water control PHS Publ No 999-WP-2
1963 22 pp
ABSTRACT This glossary contains selected
terms defined so that those not intimately
acquainted with the biological field will have
a more precise understanding of them. Its
purpose is to serve as an introduction to the
aquatic biologist's terminology.
ACCESSION NO.
KEY WORDS
Aquatic biology
Glossary
Water
Water pollution
Terminology
-I
BIBLIOGRAPHIC J R. Geckler, K. M. Mac-
kenthun, and W M Ingram Glossary of
commonly used terms in water and waste
water control. PHS Publ No. 999-WP-2.
1963. 22 pp.
ABSTRACT This glossary contains selected
terms defined so that those not intimately
acquainted with the biological field will have
a more precise understanding of them Its
purpose is to serve as an introduction to the
aquatic biologist's terminology.
ACCESSION NO.
KEY WORDS
Aquatic biology
Glossary
Water
Water pollution
Terminology
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