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.