This section is concerned with the effects of living material, both plant and animal, upon the quality and beneficial uses of water. These organisms may be primary pollutants or secondary pollutants.
The primary pollutants comprise biota that are added directly to water as a result of man’s activities such as bacteria and fungus from sewage.
Secondary pollutants represent indigenous biota such as algae and aquatic weeds, that interfere with beneficial uses of the water either by natural processes or stimulation of aquatic growths. In other words, secondary pollutants are interfering biological agents that have not been added to the water by man, but their presence and interference may be attributable to man’s management activities.
In order to more fully understand the biological responses to changes in water quality, this section will focus on definitions, terminology and significance of various major components of aquatic com unities. Emphasis will be placed on bacteria, plankton, periphyton, macrophyton, macroinvertebrates and fisheries coupled with a short discussion of the important biological calculations that are commonly used to summarize pertinent information.