10010 Introduction

10010 Introduction*
The physical and chemical characteristics of waterbodies af-
fect the abundance, species composition, stability, productivity,
and physiological condition of aquatic organism populations.
Biological methods used to assess water quality include the
collection, counting, and identification of aquatic organisms;
biomass measurements; measurements of metabolic activity
rates; measurements of pollutant toxicity, bioconcentration, and
bioaccumulation; and processing and interpretation of biological
data.
Information from these methods may serve one or more of the
following purposes:
1. To explain the cause of color, turbidity, odor, taste, or
visible particulates in water;
2. To help interpret chemical analyses (e.g., relating the pres-
ence or absence of certain biological forms to oxygen deficiency
or supersaturation in natural waters);
3. To identify the source of one water that is mixing with
another;
4. To explain the clogging of pipes, screens, or filters, and to
help design and operate water and wastewater treatment plants;
5. To determine optimum times for treating surface water with
algicides and to monitor treatment effectiveness;
6. To determine the effectiveness of drinking water treatment
stages, to help determine the effective chlorine dose in a water
treatment plant, and to indicate treatment problems or deficien-
cies;
7. To identify the nature, extent, and biological effects of
pollution;
8. To indicate the progress of self-purification in waterbodies;
9. To help determine the condition and effectiveness of unit
processes and biological wastewater treatment methods in a
wastewater treatment plant;
10. To document short- and long-term variability in water
quality caused by natural phenomena and/or human activities;
11. To provide data on the status and trends of an aquatic
system;
12. To correlate the biological mass or components with water
chemistry or conditions. (NOTE: A statistical correlation may not
always signify a cause-and-effect relationship because of the
presence of confounding variables or unknown covariates.)
The specific nature of a problem and the reasons for collecting
samples will dictate which communities of aquatic organisms
will be examined and which sampling and analytical techniques
will be used.
The following communities of aquatic organisms are consid-
ered in the sections that follow:
1. PLANKTON (Section 10200): A community of autotrophic
(phytoplankton) and heterotrophic (zooplankton, bacteria, fungi)
organisms, usually drifting or suspended in water, nonmotile or
insufficiently motile to overcome transport by currents. In fresh
water, they generally are small or microscopic; in marine or
estuarine environments, large plankters are often observed.
2. PERIPHYTON (Section 10300): A community of autotrophic
(algae) and heterotrophic (bacteria, fungi, protozoa) organisms
associated with the surfaces of submersed objects. Some are
attached, some move about. Many of the protozoa and other
minute invertebrates and algae found in plankton also occur in
periphyton.
3. MACROPHYTES (Section 10400): Large plants of all types.
They are sometimes attached at the bottom (benthic), sometimes
free-floating, sometimes totally submersed, and sometimes
partly emergent. Complex vascular plants usually have true
roots, stems, and leaves. Macroalgae are simpler but may have
stem- and leaf-like thalli.
4. MACROINVERTEBRATES (Section 10500): The invertebrates
defined here are those retained by a U.S. Standard No. 30 sieve
(0.6-mm openings). They are generally bottom-dwelling organ-
isms (benthos) that live at least part of their life cycles within or
upon available substrates in lentic (standing) and lotic (flowing)
waterbodies.
5. FISHES (Section 10600): Vertebrates of diverse morphology,
ecology, and behavior, inhabiting (and generally limited to)
aquatic systems. They have fins and gills.
6. BENTHIC MEIOFAUNA (Section 10700): The invertebrates
defined here are those that pass through a U.S. Standard No. 35
sieve (0.5-mm openings) and are retained by a No. 230 sieve
(0.063-mm openings) or No. 325 sieve (0.044-mm openings).
Benthic meiofauna include nematodes (Section 10750), express
an extreme range of morphological and life history diversity, and
have free-living, parasitic, or symbiotic trophic habits.
Large numbers of bacteria and fungi are present in plankton
and periphyton, and constitute an essential element of the total
aquatic ecosystem. Although their interactions with living and
dead organic matter profoundly affect larger aquatic organisms,
techniques for their investigation are not included herein (see
Part 9000).
Amphibians, aquatic reptiles, birds, and mammals are useful
in monitoring long-term changes in water quality and the pres-
ence of toxic substances (see Section 8930). These organisms
may be affected directly or indirectly by spills or other dis-
charges of pollutants.
Field observations are indispensable for meaningful biological
interpretations, but many biological factors cannot be evaluated
directly in the field. These must be analyzed as field data or field
samples in the laboratory. Because the significance of the ana-
lytical result depends on the representativeness of the sample,
attention is given to both field methods and associated laboratory
procedures.
Before sampling begins, clearly define study objectives. For
example, the frequency of a repetitive sampling program may
vary from hourly, for a detailed study of diel variability, to every
third month (quarterly) for a general assessment of seasonal
conditions. The scope of the study must be adjusted based on
limits in personnel, time, and budget. Before developing a study
plan, examine historic data for the study area and conduct a
literature search to identify related work elsewhere.
Whenever practicable, biologists should collect their own
samples. Much of an experienced biologist’s value lies in per-
sonal observations of field conditions and in the ability to rec-
* Approved by Standard Methods Committee, 2006.
Joint Task Group: Michael K. Hein (chair), Byron J. Adams, Steven N. Francoeur,
Donald J. Klemm, Ernst B. Peebles, Donald J. Reish, Miles M. Smart, Ann St.
Amand, Paul V. Zimba.
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ognize signs of environmental changes as reflected in various
aquatic communities. Detecting environmental changes also de-
pends on the accurate and consistent identification of the organ-
isms present. Sections 10600 (Fishes), 10750 (Nematological
Examination), and 10900 (Identification of Aquatic Organisms)
include basic keys, drawings of organisms, and selected refer-
ences to help biologists identify the plants and animals collected
in field surveys. However, these cannot fully replace examina-
tion by taxonomic experts for key groups.
The primary orientation of Part 10000 is toward field collec-
tion and associated laboratory analyses to help determine the
status of aquatic communities under field conditions and inter-
pret the influence of past and present environmental conditions.
Principal emphasis is on methods and equipment, rather than on
interpretation or application of results. The complex interrela-
tionships existing in an aquatic environment often require many
field and laboratory procedures, so frequent cross-references
between sections have been made.
Many other types of studies may be, and are being, conducted
that are oriented more toward laboratory research. Such labora-
tory studies will develop further basic knowledge of community
and/or organism responses under controlled conditions and will
help predict the effects of future environmental changes on
aquatic communities. However, such studies are not within the
scope of Part 10000.
(10010)/Introduction
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(10010)/Introduction