WATER QUALITY: Technical Information - Briefing papers on aquatic biology

                                            August 14, 1974

QUALITY OF WATER BRANCH TECHNICAL MEMORANDUM N0. 75.03

Subject: WATER QUALITY: Technical Information - Briefing papers 
                        on aquatic biology

With implementation of the national stream quality accounting 
network (NASQAN), many Division personnel have been introduced to 
a new aspect of water quality--the field of aquatic biology. The 
operational design of NASQAN currently includes the collection of 
samples for indicator bacteria, phytoplankton, and periphyton. 
Additionally, many Districts now are expanding state water-quality 
networks to include the collection of biological information and 
many new biologically oriented interpretive projects are being 
added to the cooperative program.

In order to increase the awareness and understanding in the 
Division of the role and significance of biological quality, the 
Quality of Water Branch, wlth the assistance of its Task Group on 
Biology and Microbiology, is preparing and will distribute during 
the next few months a series of briefing papers on aquatic 
biology. Each briefing paper will discuss a separate topic and 
will be prepared in a simple, easy-to-understand manner. The 
briefing papers should be circulated as widely as possible in all 
districts and project o#fices.

The first briefing paper, "Why biology in water-quality studies?", 
is attached. Future briefing papers may include the following 
topics:

Stream biology
Biological indices of water quality
Diversity indices
Phytoplankton
Periphyton
Plant pigments
Biological productivity
Algal growth potential (AGP)
Adenosine triphosphate (ATP)

The Ouality of Water Branch would appreciate receiving comments on 
the effectiveness, use, and future value of this series of 
technical briefing papers.

                
                                 R. J. Pickering

Attachment

WRD Distribution: A, B, FO-L, PO

          WHY BIOLOGY IN WATER-QUALITY STUDIES?
                    Phillip E. Greeson

Recently, many personnel of the Water Resources Division have been 
exposed to a new technical vocabulary. Terms such as periphyton, 
phytoplankton, artificial substrates, benthic invertebrates, 
biota, biomass, biological indices,and so on are appearing more 
frequently in memorandums, publications, and planning documents. 
All of these terms relate to the biological activities of our 
water-quality programs.

We may well be pondering the question, "Why biology in water 
quality studies?" Let us pursue the question. Without attempting 
to delve deeply into theoretical aspects of aquatic biology, it 
will suffice to look very briefly at some recent events and 
aquatic ecological principles.

The Water Pollution Control Act Amendments of 1972 were enacted 
for the purposes of assuring supplies of water suitable for 
domestic uses, agricultural uses such as irrigation and stock 
watering, power generation, and industrial processes; restoring 
and maintaining aesthetically pleasant waters for recreation; and 
ensuring water of the quality needed for the survival, growth, and 
reproduction of fresh-water and marine life.

A careful examination of these purposes reveals that the 
maintenance of high-quality waters is to provide conditions 
suitable for living things - including man - and are thus 
biologically significant. As we look deeper into the causes and 
effects of water quality, we find more and more aspects that fall 
within the field of aquatic biology.

For many years, the investigations of water quality have been 
approached in narrow and parochial ways. The reasons are many and, 
perhaps, justified. Until the rather recent inclusion of indicator 
bacteria determinations in WRD activities, water-quality studies 
consisted of the collection of selected physical and chemical data 
and interpretation of that data.

The WRD, in the design of its newly implemented national stream 
quality accounting network (NASQAN) has expanded its water-quality 
efforts to include several biological determinations, in addition
to bacteria.

Although physical, chemical, and bacteriological measurements 
provide information for evaluating water quality, there are 
limitations to evaluation based exclusively on these variables. 
Physical, chemical, and bacteriological determinations, for 
example, represent, for the most part,conditions only at the time 
of sampling. Chemicals that influence water quality are numerous, 
vary widely in concentration, form complex compounds, and interact 
with the physical properties in numerous ways to produce a wide 
range of effects; therefore, dependence upon this type of 
information alone may be inadequate for fully characterizing water 
quality. Aquatic organisms, on the other hand, respond continually 
to the environment, reflecting in their numbers and kinds, the 
interactions of all chemical, physical, and biological factors,

To calculate the average value of an environmental variable (for 
example, a nutrient) or to sample some aspect of water quality at 
a point in time is not a measure of the suitability of an 
environment for sustaining life. It is the magnitude and duration 
of the extremes of environmental conditions that are important. 
Aquatic organisms, by virtue of the requirements for their 
existance, represent those extremes.

Every organism, whether aquatic or terrestrial, requires certain 
physical and chemical conditions for its existence. If any 
condition falls below or exceeds a certain point, the organism 
dies or moves away, and there is a change in the number and kinds 
of organisms remaining. For example, one would not expect to find 
a tropical anglefish in an Arctic stream because the water is too 
cold nor to find a largemouth bass in the salty ocean because the 
dissolved solids content is too high. All organisms have 
ecological minimum and maximum limits, with a range in between 
which represents the "limits of tolerance."

The limits of tolerance are specific for every organism. A 
condition that is suitable for one organism may be entirely 
unsuitable for another. Similarly, the lower limit of tolerance 
for one organism may be the upper limit of tolerance for another. 
The ranges of tolerance also vary between organisms. Figure 1 is a 
diagrammatic representation of variations in tolerance limits.

Figure l.--Comparison of tolerance limits for organisms A, B, 
           and C.

In the figure, organism A cannot exist under the same condition as 
organism C. Organism B, however, could exist with either organism 
A or organism C. The limits of tolerance #or organism B are widely 
separated, therefore, its range of tolerance is greater than that 
for organism A whose limits of tolerance are relatively close.

Because the tolerance limits of individual organisms vary widely, 
the flora and fauna of streams and lakes are indicators of 
environmental extremes and integrators of environmental qualitiy. 
In other words, a knowledge of the numbers and kinds of organisms 
in an aquatic community is a measure of local water-quality 
conditions.

Ideally, all segments of an aquatic community should be defined in 
the evaluation of water quality; but because of limitations in 
time, expertise, and budgets, biological studies usually are 
limited to the study of a few major groups of aquatic organisms. 
Five groups of organisms traditionally have been studied as 
indicators of water-quality conditions-bacteria, fish, plankton, 
periphyton, and benthic invertebrates. The bacteria serve as 
indicators of fecal contamination and the presence of pathogenic 
organisms. Fish are somewhat unsuitable for water-quality studies 
because their superior mobility enables them to cover great 
distances and, therefore, to avoid many undesirable conditions.

Plankton, because they float passively with the currents, are 
indicative of quality conditions of the mass of water in which 
they are contained. Estimation of the plankton population 
indicates, in part, the nutrient-supplying capability of that mass 
of water. A similar definition possibly could be derived by 
chemically analyzing the water for all known nutrients, a 
formidable and expensive task. Periphyton also provide an
indication of the nutrient-supply in water; and, in addition, 
because of their stationary or sessile existence, they represent 
an integration of the chemical and physical conditions of water 
passing the point of their location.

Benthic invertebrates are excellent indicators of stream 
conditions, primarily because they are restricted to the area in 
which they are found. The various kinds of invertebrates are 
somewhat well known for their limits of tolerance, their life-
histories are usually sufficiently long to respond to 
environmental changes, and the presence or absence of particular 
groups is indicative of quality. Benthic invertebrates, because of 
their varying environmental requirements, form communities 
characteristic or associated with particular chemical and physical 
conditions. Biologists now know that the presence in water of 
immature insects, such as mayflies, caddisflies, and stoneflies, 
and certain molluscs and crayfish usually characterize relatively 
"clean" water conditions. On the other hand, the presence of 
sludge-worms, midges, air-breathing snails, and aquatic earthworms 
is indicative of the presence of oxygen-consuming organic 
materials. It is significant to recognize that the number of 
different kinds of invertebrate organisms present, rather than the 
numbers of individuals of a particular kind, is of greater 
importance as an indicator of quality conditions.

The complete absence of aquatic biota in an otherwise clean-
appearing stream may indicate the presence of toxic substances. 
Sublethal levels of toxicants may be detected by analyzing the 
flesh of organisms, because the toxicants can be concentrated 
through food chains.

Surveys of aquatic organisms often result in extensive lists of 
latinized names of species and numbers of individuals per species. 
Needless to say, this type of information is in fact one measure 
of water quality, in just the same manner as a list of the 
concentrations of dissolved inorganic substances is another 
measure of water quality. The interpretation of aquatic biological 
data, however, generally rests with the trained and experienced 
biologist. Such a condition will gradually change as specialists 
in other disciplines become familiar with the basic concepts and 
principles of aquatic ecology. This has already begun in our work 
of determining indicator bacteria.

One of many .tools used to simplify the analysis and 
interpretation of biological data is the diversity index. The 
diversity index is the ratio of the number of species or taxa to 
some other important value, usually the total number of organisms 
in a sample of a community. It is a measure of the evenness of 
distribution of individuals within the community.

The concept of the diversity index is based on the assumption that 
good quality waters generally have higher diversity values because 
the benthic community contains many species of relatively equal 
abundance. Poor-quality waters generally have low diversity values 
because many pollution-sensitive species are eliminated from the 
community and a few tolerant organisms thrive in the absence of 
competition and the presence of an abundant food supply.

It is important to recognize that biological data do not replace 
chemical and physical data any more than chemical and physical 
data replace biological data~ They provide converging lines of 
evidence over time that supplement one another; they are not 
mutually exclusive.

To answer the question, "Why biology in water-quality studies?", 
one must correctly say that aquatic biology is one important 
aspect of water quality.