Aquatic Invertebrates as Indicators of Stream Pollution

Year-round field studies of the biology of stream sanitation were initiated by the biology section of the Public Health Service's Environmental Health Center on Lytle Creek in Octo- ber 1949.The aims of these investigations were:1. To develop or devise and field test pro- cedures and equipment for biological surveys and investigations of polluted streams.2. To investigate seasonal and diurnal en- vironmental changes in a stream polluted with oxygen-depleting wastes.3. To determine how the physical-chemical environment in the various pollutional zones affects the qualitative and quantitative com- position of aquatic populations and how these populations in turn affect or change physical- chemical conditions. 4. To relate various qualitative and quantitative compositions of aquatic populations to en- vironmental conditions found in streams pol- luted with organic wastes and to test the value and use of aquatic organisms as indicators of clean water and various degrees of pollution at all seasons of the year.5. To determine the rate of satisfaction of biochemical oxygen demand (BOD), the area in which most of the demand is satisfied, and how seasonal and other environmental condi- tions affect the process.6. To determine the value of fishes as indica- tors of pollution and their use in evaluating the effects of pollution.The composition of the aquatic fauna in