Aquatic Invertebrates as Indicators Of Stream Pollution By ARDEN R. GAUFIN, Ph. D., and CLARENCE M. TARZWELL, Ph. D. Year-round field studies of the biology of various sections of the stream and diurnal stream sanitation were initiated by the biology changes in environmental conditions are dis- section of the Public Health Service's Environ- cussed here. mental Health Center on Lytle Creek in Octo- Lytle Creek, which was especially selected ber 1949. The aims of these investigations for the study, is about 45 miles northeast of were: Cincinnati, Ohio, and is a tributary of Todds 1. To develop or devise and field test pro- Fork, a part of the Little Miami River system. cedures and equipment for biological surveys It is a small stream approximately 11 miles and investigations of polluted streams. long, 3 to 35 feet wide during non-floodstage, 2. To investigate seasonal and diurnal en- and a few inches up to 6 feet deep. The prin- vironmental changes in a stream polluted with cipal natural source of water in the stream is oxygen-depleting wastes. surface drainage from the surrounding area. 3. To determine how the physical-chemical Some 7 miles above its mouth, the creek receives environment in the various pollutional zones the effluent from the primary sewage treatment affects the qualitative and quantitative com- plant of Wilmington, Ohio, a city of about position of aquatic populations and how these 10,000 people. Lytle Creek is particularly fa- populations in turn affect or change physical- vorable for studies of the pollutional effects of chemical conditions. oxygen-depleting wastes because it has only 4. To relate various qualitative and quantita- one source and type of pollution (domestic tive compositions of aquatic populations to en- wastes from Wilmington) ; it has no permanent vironmental conditions found in streams pol- tributaries below the source of pollution; and luted with organic wastes and to test the value it has all degrees of pollution from a definite and use of aquatic organisms as indicators of septic zone through recovery and back to clean clean water and various degrees of pollution at water.' all seasons of the year. 5. To determine the rate of satisfaction of biochemical oxygen demand (BOD), the area Procedures in which most of the demand is satisfied, and One of the early objectives of the Lytle Creek how seasonal and other environmental condi- investigations was to evaluate the reliability tions affect the process. and possible use of aquatic organisms (chiefly 6. To determine the value of fishes as indica- benthic forms) as indicators of the extent and tors of pollution and their use in evaluating the severity of pollution and the degree of stream effects of pollution. recovery. Plans were made for a comprehen- The composition of the aquatic fauna in 'Zones of pollution, as herein considered for Lytle Creek, are based principally on the amount of dissolved Dr. Tarzwell is chief and Dr. Gaufin is biolo- oxygen occurring throughout the stream. The septic ist of the biology section of the Public Health zone is the area of stream showing oxygen depletion during at least some portion of the year. It grades Service Environmental Health Center, Cincnn- gradually into the recovery zone where the minimum nati, Ohio. oxygen concentrations range from 0.1 to 2 ppm. In the clean-water zone minimal oxygen concentrations may be as low as 2 ppm for short periods of time. Vol. 67, No. 1, January 1952 57 sive study. A detailed survey was made of the These data were then correlated with those ob- stream and a map prepared showing the loca- tained by the quantitative and qualitative tion and extent of pools, runs, and riffles, and studies of the benthic, marginal, and surface the stream profile and gradient. A sharp crested rectangular contracted weir and contin- uous float level recorder were placed in the stream about 3 miles above its mouth for the continuous recording of flows. During the winter and spring, flows average 7 cubic feet per second (cfs) with about 6 to S frequent floods of 40 cfs or more. In late 2."9.0 summer and fall, flows are generally small, 0 about 0.1 cfs above the sewage plant outfall and 0~8.0 Io 7.0 1 cfs below it. During periods of low summer ~0 flow, the sewagre plant effluent overwhelms the 0~6.0 Minimui stream with oxygen-depleting wastes and causes .15.0 a septic zone to be produced immediately below 4.0 tlle outfall. 3.0 Ten stations were selected along the stream 2.0 course for periodic sampling in all zones. These 1.0 stations were desiginated by their distance in --- miles upstream fiom the mouth, as stations: 0.0 -T -T- 0, 1, 2.8, 4.2, 5.2, 6.5, 7.2, 7.3 (sewage outfall), Miles 8.7 7.6 7.2 6.5 5.2 4.2 2.8 1.0 0.O 7.6, and 8.7. Monthly, or more frequently, sam- Actual distances between stations ples were taken at these stations for the deter- Range in dissolved oxygen, Lytle Creek, August 22-23, 1951. mination of dissolved oxygen, pH, CO2, methyl orange, and phenolphthalein alkalinity, and fauna to provide information on (a) aquatic temperatures. Quantitative bottom samples populations which can be expected to develop were taken at monthly intervals at each station under certain ecologic conditions, and con- in pools, runs, and riffles. A Surber square- versely (b) environmental conditions or varia- foot samnpler was used in riffle areas, while a tions in environmental conditions which are in- Petersen or Ekman dredge was used in other dicated by various compositions and densities of areas. Marginal samples were also taken, and aquatic organisms. reconnaissance surveys of bottom and surface fauna were made along the entire stream. (BOD studies have been made periodically at Results all stations, as well as plankton, microbottom The chemical and physical data collected dur- fauna, and fish population studies.) ing 6 sampling runs for the 10 stations are In the Lytle Creek investigations emphasis enumerated in table 1. These data present the was placed on year-round studies to determine maximum and minimum oxygen concentrations seasonal variations in aquatic populations and in the stream ecologic conditions. Attention was also di- and water temperatures occurring and summer months. rected to diurnal variations in physical and during the early spring chemical conditions, especially duringr the Since a wide difference in the amounts of spring and summer when they are more pro- oxygen present in the stream during day and nounced. Physical-chemical variations were night was noted, special attention was paid to determined by taking hourly samples at each of lhourly variations in the dissolved oxygen con- the stations for a 24-hour period. By these and tent. The range of these variations for the other studies, information was obtained con- period 9: 00 a. m. August 22 to 8:00 a. m. Au- cerning ecologic conditions and their diurnal gust 23 is presented in the chart. During the and seasonal variations in each of the zones. reconnaissance surveys, conducted in connec- s8 Public Health Reports tloll vitl the samiipliing rulns, 68 genera and 79 sp., were abunidant. Of the 23 species of may- species of animals were collected and identi- flies, stoneflies, and caddisflies taken, only one fied. Of these species, 29 percent were Diptera, species, Callibaetis sp., occurred outside of the or fly larvae, a group which is adapted to live clean-water zone. The organisms collected at un(der a wide variety of environmental condi- five stations representative of each of the zones tions. Fifteen species of organisms were taken are listed in table 2. Their comparative abun- in the septic zone, but only six of them, Chi- dance by month and zone is also indicated. ronomfUs tentans, Cule pipiens, Eristalis sp., Among the primary requisites for animal Physa integra, Li?nnodrilus sp., and Tubifex existence are oxygen and food. When estab- Table 1. Summary of physical and chemical conditions in Lytle Creek, 1951 Dates of hourly sampling over 24-hour period Station Range 4/24/51 5/1/51 5/9, 10/51 6/28,29/51 8/15/51 8/22, 23/51 - | S] ---- D. 0 15 ppm--- - 13.9 - - - |82.6|||450pp.pppm. 8.7 | aximinum1TenpTe - 63-. p - ----- -- 590. -M n m m 8.450 7D. 0 6----- ppm - - - - - 4.5 ppm. Miaximum{TemP-----| 62 m-- - 770I D.O 14.7 = ---=- 8.8 ppm. 7.6 ppm 5 Mininimum{Teinp- 470 --- 81°-------- ppm----0--61p. D. 0 ------ 7.2 ppm-- -- - - - 0 ppm. 5Maximum{TemP 590 - 710.pm---------------------- 710. 7.2Al D. O 12.1 ppm | 0.8 m | O-------|---7]° 0.2pp,. m 480 - 680. 7.2ir m e -- ND. ----6.0 ppm -------------- -- -----------0.0 ppm. 6.5MaY ~fTemp- - -60g..- 700.... 810.... 790 --- 790. D 0 ------11.2 ppm. 14. ppm1 1. ----| | 0.8 ppm. 4 2 M0taximum T -------| ppm-- -40.2ppm _ 5 -lin.i.5um -5-ppm -- ----- 65°--- 710 ------- 64.50 ------ 610. ND. O 4.7 ppm --- 0.6 ppm... 0.0 ppm... 0.0 ppm.... 0.0 ppm. Mfaximrum{Temp- 60.50 ----760-----700-----80.50--- 800-----750. 5.2 D. 0 ----12.4 ppm- 19.1 ppm- 19.4 ppm..- 11.6 ppm- 7.3 ppm..-.-.. 6.9 ppm. Alinimurlm JTemp...... 540 ----- 650 -----590------770 710----- 610. ND. O 5.4 ppm... 0.8 ppm---- 2.9 ppm.... 0.2 ppm-.. 0.0 ppm... 0.2 ppm. em 4.2 ai km 660 -- 760 770 -- 71.50. 4.2 ND. 0 16.4 ppm..- 18.1 ppm--------------- 5.4 ppm....- 5.5 ppm.