10010 Introduction* 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 organisms (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 presence of toxic substances (see Section 8930). These organisms may be affected directly or indirectly by spills or other discharges 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 analytical 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 personal observations of field conditions and in the ability to rec- The physical and chemical characteristics of waterbodies affect 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 presence 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 deficiencies; 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 considered 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. * 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. 1 (10010)/Introduction ognize signs of environmental changes as reflected in various aquatic communities. Detecting environmental changes also depends on the accurate and consistent identification of the organisms present. Sections 10600 (Fishes), 10750 (Nematological Examination), and 10900 (Identification of Aquatic Organisms) include basic keys, drawings of organisms, and selected references to help biologists identify the plants and animals collected in field surveys. However, these cannot fully replace examination by taxonomic experts for key groups. The primary orientation of Part 10000 is toward field collection and associated laboratory analyses to help determine the status of aquatic communities under field conditions and interpret 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 interrelationships 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 laboratory 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. 2