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 were collected and identi- , stoneflies, and caddisflies taken, only one fied. Of these species, 29 percent were Diptera, species, Callibaetis sp., occurred outside of the or 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 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. e Miir[ M p 540. -- 650.- --- 720 ------550. LD. O ---- 6.5 ppm... 1.0 ppm.----..------1.4 ppm- 2.0 ppm. . Maximum1Temp - - - - - 690 790 870 870 800. 2.8 ID.O. ---- 13.8 ppm.... 14.3 ppm...... 10.1 ppm... 12.3 ppm.... 14.7 ppm. Minimum Temp....-. 540 650 720.pp 72-. 590. ND. 0.--- 8.1 ppm. -.... 1.6 ppm..-.-. 3.6 ppm....- 1.6 ppm.... 3.2 ppm. -1-01 I- I. . Alaximum Temp- - - - - 70 700..... 730. 1 ND. -0-.-. - 13.5 ppm 14.2 ppm.. 9.6 ppm. Minimum' Tem. 5406.p 580 ._ 65.50. 6.9 ppm...... - 5.2 ppm...... 5.3 ppm. II I.I,

maximum1Temp...... ------750. 0 ND. - ---- 11.6 ppm. Minimum'Temp...... 63.50. ND. 0.--- 5.0 ppm. _1 - _ II I___ _I Todds Maximlum Temp.------700. Fork ND. 0.------10.7 ppm. Mfinimum'Ternp...... 62.50. ND. 0 ---- 5.1 ppm.

Vol. 67, No. 1, January 1952 59 Table 2. Distribution of invertebrates in Lytle Creek, May and August 1951

Stations I

Organisms i 8.7 6.5 5.2 4.2 _ 2 -_ __ M -_~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ May , Aug. May Aug. May Aug. May Aug. May Aug. .1 DIPTERA Chironomus flavus 2 p P p Chironomus tentans - ---- p A P p Chironomus flavicingula P P ------I--p P Chironomus quadripunctatum P P-- Chironomus sp. A P Chironomus sp. B P

Pentaneura flavifrons P - - Dictya sp Anopheles punctipennis P Culex pipiens- p A A p A Eristalis sp A A Stratiomyia sp P P P Nemotelus sp P -P Tabanus sp - - P- -P p p P Palpomyia sp P- -P P Stilobezzia sp- -P P p --I--- P argentata . p Simulium vittatum P P Hemerodromia sp- . PP [ P Pilaria sp - - ---i-- P Tipula sp - - - -ii- 1- -ii--PP Eriocera sp - P Paradixa - - sp p -I --i---p COLEOPTERA p p - -i ---- Stenelmis crenata______p Stenelmis sp Simsonia quadrinotata Bidessus sp. A P Laccophilus sp Berosus sp- -I---- Tropisternus lateralis- p p P Tropisternus sp p p 7-- p p Laccobius sp- p p p P Peltodytes sp P P Gyrinus sp ------Dineutes sp- EPHEMEROPTERA Pp Baetis cingulatus- p P Baetis parvus ------p P Caenis sp p ---I--p p

Callibaetis sp-- p ------p Isonychia albomanicata- p P Stenonema femoratum _ -_ p p Stenonema ohioense _ p p p I I See footnotes at end of table. lishlinlg biological indices of pollution, such stream. From the standpoint of dissolved requisites must be taken into consideration. In oxygen, the stream was satisfactory for most Lytle Creek from November 15,1950, to April 1, types of bottom organisms throughout its 1951, the volume of flow was more than 6 cfs length during the entire period. Chemically, on all except three occasions. The time of flow the water appeared to be relatively free from from the sewage outfall to the mouth at Todds harmful pollution, but the fauna that was pres- Fork never exceeded 48 hours. Water tempera- ent still reflected the critically low oxygen tures were under 600 F., and oxygen concentra- concentrations occurring in the past. tions approached saturation throughout the From April 1 to October 1, the volume of flow 60 Public Health Reports Table 2. Distribution of invertebrates in Lytle Creek, May and August 1951-Continued

Stations I

Organisms

TRICHOPTERA Brachycentrus americanus P Cheumatopsyche sp p p P P Hydropsyche betteni p P P HIydropsyche bifida p P P Chimarra obscura P P p .-- Dolophilus shawnee Pp p~~~~~~~~~~~ Phyacophila lobifera _ p _-- Ochrotrichia sp p _-- Hydroptila consimilis p _-- Hydroptila sp p PLECOPTERA Acroneuria evoluta p Allocapnia viviparia P Nemoura venosa P Perlesta placida P _- Neoperla clymene p Isoperla minuta ODONATA Plathemis sp p p P Paltothemis sp p Argia sp --P-P- p P Agrion sp -- -I---p Enallagma sp p P NEUROPTERA P Corydalis cornutus- Sialis sp- p P-P P HEMIPTERA Belostoma sp p p p p p P Corixidae p p p p P Gerris sp p p p P Microvelia sp ------p P Notonecta sp _ p Ranatra sp .- p CRUSTACEA Asellus sp P p ------Cambarus rusticus Pp p p p Hyalella sp ------p --- MOLLUSCA p Physa integra ------P Sphaerium solidulum - - p p p p p A p A p p A- ANNELIDA Limnodrilus sp- p A p A p A p p Tubifex sp p A p A p A p p (l108Tphonia spee p------p p P L1- Total -- 10 species per station_ 40 29", 9 10 10 19I 37 11 10 I The stations are 2 classified into zones of pollution as follows: clean 8.7 and zone, 6.5 and zone of 4.2. A=abundant; P=present. water, 2.8; septic 5.2; recovery,

Vol.67, No. 1,January 1952 61 977220-52 dropped to an average of 1 cfs, the time of flow floods, and abundant food, prevailing through. extended to 7 or 8 days, water temperatures rose out the summer of 1951, a surprisingly large to as high as 870 F., and oxygen concentrations and varied macrobottom fauna developed ill became critically low in the 4-mile section of the stream. This condition was observed dur. stream below the sewage treatment plant out- ing May and again in August when special col. fall. Definite pollutional zones were estab- lections of aquatic organisms were made at all lished in May and persisted throughout the sampling points along the stream, and their dis- summer. An abundant food supply and a tribution correlated with the diurnal physical variable oxygen supply below the treatment and chemical conditions prevailing at the vari- plant outfall resulted in a distinctive fauna in ous stations. each of these zones. In evaluating aquatic organisms as indicators Critically low oxygen concentrations were of pollutional conditions, great caution must be found in the stream during the night at station used because of several complicating ecologic 6.5 as early as May 9. Concomitant with the conditions. First, many organisms which occur low nocturnal values, remarkably high oxygen in large numbers in extremely polluted water concentrations were recorded during the after- may also be found in limited numbers in cleaner noon at the same station. Peak concentrations situations. Several species of invertebrates, of oxygen for the season occurred before the such as the mosquito, (u1ea pipi ; beetle, deciduous stream-side trees began to exercise a Tropi8ternmw sp.; and sludgeworms, Limrnod- shading influence. A dissolved oxygen value of riWm and Tubifeac spp., which occurred in 19.4 ppm was found at station 5.2 at 3 p. m. on abundance at stations 6.5 and 5.2, also occurred May 9. This peak was produced by a heavy in the clean-water zones. Second, many species plankton bloom. When marginal vegetation listed in table 2 occurred in such small numbers shaded the stream, blooms became less marked as to discourage their individual use as indi- and daytime oxygen values were not as high. cators. Third, several ecologic factors other As the summer advanced, oxygen depletion than the presence of a pollutant may limit the became of progressively greater duration and distribution of certain species; for example, extent. The result was a well-defined oxygen- erosion, floods, the size of the stream, the type less zone extending from the sewage treatment of bottom, the flight range of the , and plant outfall to a point 2 miles downstream, as the portion of the stream under study. It is indicated by studies carried out on the night of believed that the moderate abundance of single August 22. This depletion persisted through- species should not be considered as biological out the day at stations 7.2 and 6.5. The range indicators of pollution because organisms such in hourly dissolved oxygen values found late in as Tubl3fex usuaRly associated with polluted August at the various sampling stations along areas are also found in clean waters. It is the the stream is shown in the chart. complex or association of organisms which is important for indicating clean or polluted Discussion water. All organisms present and their rela- tive abundance must be considered. One of the primary objectives of the Lytle In satisfactorily using associations of aquatic Creek studies has been to arrive at a better defi- organisms as indicators of pollution, the ab- nition of indicator organisms. The finding of sence or much reduced numbers of formerly certain organisms, such as rat-tail maggots, present clean-water species in an area may be Eristalis sp.; sludgeworms, Tiubifex tubifex; as important, or more so, as numbers of known and bloodworms, Chironamus tentanm, presents pollutional forms (2). In this connection, table important evidence of the pollutional condition 2 shows that such as mayflies, caddis- of a stream (1), while the absence of cleaner flies, stoneflies, and hellgramites were almost water forms is likewise a valuable measure of entirely limited to the clean water occurring at existing conditions. stations 8.7 and 2.8. The only exception was a With favorable ecologic conditions, such as mayfly, Callibaeti sp. This form was collected high temperatures, uniform flow, freedom from in a marginal surface sample and evidently had

62 Public Health Reports been able to obtain sufficient oxygen from the these forms to attain a great abundance in surface film to survive. polluted areas. The absence of organisms, which are indica- When conditions are favorable for organisms tive of clean-water conditions, from a section of which can adapt to pollution, they thrive and stream should not always be taken as definite build high populations (4). For this reason, indication of pollution. A knowledge of the the society of organisms found in zones of pol- life histories of the various groups of aquatic lution is highly significant in offering clues insects often is helpful in interpreting the mean- to the intensity of pollution and the degree of ing of their distribution. For example, in the recovery. If changing conditions brought collection of invertebrates made in August, only about by pollution are unfavorable, organisms one species of stonefly and five species of cad- must resist these changes, migrate, or be de- disflies were represented. In the May collection stroyed. Since many of the species of insects five species of stoneflies and nine species of found in Lytle Creek are found in both the caddisflies were present. Their absence later on lower and upper sections of the stream but are was due to their emergence as adults during the missing in the pollutional zones, and since such intervening months. Similarly, the absence of organisms are continuous in other nonpolluted some beetles, dragonflies, and damselflies in the streams in the area, it seems probable that pol- earlier collections was partly due to their pres- lution is responsible for their discontinuous ence in immature stages so that they were distribution in Lytle Creek. missed or overlooked. In a stream polluted with organic wastes, a Apart from the fact that pollutional organ- certain reduction of the supply of dissolved isms must be found and clean-water species oxygen may occur in a certain section through- must be missing in delineating the zones of out the year, during the summer months, or pollution in a stream, the mode of occurrence for only a few days in the year. Because pol- of the organisms must be taken into account lution surveys frequently cannot be made dur- (3). For example, the assemblage of organ- ing the period of critical conditions, and isms found in the polluted zones of Lytle Creek chemical studies give information on physical- presented the following characteristics: (a) chemical conditions only at the time of sam- very large numbers of individuals; (b) few pling, there is need for additional methods species represented in the fauna; (c) princi- which can be used throughout the year for de- pally scavenger types present; and (d) the termining over-all conditions and the extent presence of forms having low oxygen require- and severity of brief critical or limiting en- ments or special adaptations for obtaining their vironmental factors. The qualitative and quan- oxygen supply. Not over 10 different species titative composition of an aquatic population of macroinvertebrates were taken from sta- is determined by recurring critical conditions, tions 6.5 and 5.2 in the septic zone at any one even though of short duration, as well as the time, while as many as 40 species were found more stable or long-time environmental fac- in the clean-water zones (table 2). However, as tors. Therefore, the complex of organisms many as 3,000 Culew, pipien. or 20,000 Tubificids which develops in a given area is in turn in- were collected per square foot sample in the dicative of environmental conditions which septic zone, while no species exceeded 500 in- have occurred during its development. Or- dividuals per square foot in the clean-water ganisms having life histories of a year or more area. All the insects occurring in the septic will thus serve to indicate unfavorable or lim- zone have special adaptations for obtaining iting conditions that have occurred several oxygen, such as the caudal respiratory tubes of months previously. Because aquatic popula- the mosquito and rattail maggot or the air tions are a result of past environmental condi- tions, they serve as a means for determining space under the elytra of the beetles. With such conditions in a stream. They are espe- such adaptations, depletion of oxygen in the cially valuable because they can be used during water does not serve as a barrier to their dis- fall, winter, or spring months, when flows are tribution. An abundant food supply enables large, dilution is at a maximum, dissolved oxy- Vol. 67, No. 1, January 1952 63 gen is near saturation, and visual evidence of able index in delineating zones of pollution in a pollution at a minimum, to delineate former stream. septic areas or to indicate critical conditions of 4. In interpreting the distribution of orgal- short duration. isms in a stream as an index of pollutional con- In order to utilize aquatic populations in this ditions, all environmental factors should be con- way, however, it is essential to have a knowledge sidered. of the species composition and abundance of the 5. Pollutional associations are characterized various organisms in the population under the by few species but large numbers of individuals. various ecologic conditions which prevail in 6. The association of organisms normally clean and in polluted waters. Further, consid- present under most septic conditions is charac- eration must be given to the fact that pollution terized by the absence of plant and animal eaters with organic wastes is only one of the several and the presence of scavengers. environmental factors determining the compo- 7. Organisms characteristic of septic zones sition of aquatic populations. Other environ- are those which can exist under conditions of mental factors, such as type, size and character very low oxygen or have adaptations for breath- of the stream, variations in flow, severity of silt- ing atmospheric oxygen. ing, floods and erosion, water temperatures and 8. Nocturnal deficiencies in dissolved oxygen the character of the watershed, are all important are often the critical environmental factor in determining the make-up of aquatic popula- which determines the distribution of organisms tions. Occasionally, there is a sparsity of bot- in a stream. tom organisms which makes the drawing of any 9. Under conditions of organic pollution conclusions in regard to organic pollution diffi- diurnal-nocturnal deficiencies in oxygen are cult. sometimes concomitant with supersaturation of However, one who has knowledge of and dissolved experience with aquatic organisms can, by a oxygen. reconnaissance survey, learn a great deal about the severity and extent of pollution and the ACKNOWLEDGMENTS extent of stream recovery even though the sur- An investigation of this type requires the services of vey is made at a time of year when the physical- a considerable number of people. The entire staff of chemical indicators of pollution are least the biology section has assisted in certain phases of evi- the study, and their contributions are acknowledged. dent or largely absent. The authors express their appreciation for extensive assistance to Dr. 0. M. Palmer, George Paine, Harold Walter, Jack Hammond, Dr. Max Katz, and Thomas Conclusions Maloney. 1. Single species of organisms such as Tubi- fex tubifex, or Clhiroinowm tentanm cannot be REFERENCES used safely as indicators of pollution unless (1) Bartsch, A. F.: Biological aspects of stream pollu- their relative abundance is considered. tion. Sewage Works Journal 20: 292-302 (1948). 2. The absence or much reduced numbers of (2) Richardson, R. E.: The bottom fauna of the Mid- dle Illinois River, 1913-1925. Ill. Nat. Hist. formerly present clean-water species constitutes Surv. Bull. 17: 387-475 (1928). an important index in evaluating the degree of (3) Whipple, G. S.: The microscopy of drinking water. pollution. Ed. 4. New York, John Wiley and Sons, 1948. 3. The quantitative and qualitative composi- (4) Lackey, James B.: Stream microbiology. In Stream sanitation, by Earle B. Phelps. New tion of an aquatic population constitutes a valu- York, John Wiley and Sons, 1944.

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