The effects of nutrient renewal, conservation pool water level, and the average weekly discharge rate on the species composition, relative abundance, and population fluctuations of the Copepoda and Cladocera of Red Rock Reservoir were determined. The average retention time (flushing rate) was 11.2 days. Twenty-one species were identified with the dominants being Cyclops spp., Diaptomus spp., Daphnia spp., Bosmina longirostris, Moina micrura, Ceriodaphnia quadrangula, and Diaphano-soma spp. Three distinct seasonal peaks in population growth were noted. Population fluctuations showed slight correlation with temperature, transparency, discharge rate, nutrient levels and no relationship was seen with water level. A time interval of 18 to 32 days occurred between high nitrate and phosphate levels and population abundance peaks. Species composition showed distinct seasonal changes. Population numbers began increasing at the dam area and continued upstream with declines following the reverse pattern

Asch, Ronald L.

Kingsbury, Phyllis J.

English

University of Northern Iowa

Proceedings of the Iowa Academy of Science Volume 78 Number 3-4 Article 13 1972 Copepoda and Cladocera Populations of Red Rock Reservoir, Iowa from April to November, 1970 Ronald L. Asch Eureka Senior High School Phyllis J. Kingsbury Drake University Copyright ©1972 Iowa Academy of Science, Inc. Follow this and additional works at: https://scholarworks.uni.edu/pias Recommended Citation Asch, Ronald L. and Kingsbury, Phyllis J. (1972) "Copepoda and Cladocera Populations of Red Rock Reservoir, Iowa from April to November, 1970," Proceedings of the Iowa Academy of Science, 78(3-4), 73-75. Available at: https://scholarworks.uni.edu/pias/vol78/iss3/13 This Research is brought to you for free and open access by the Iowa Academy of Science at UNI ScholarWorks. It has been accepted for inclusion in Proceedings of the Iowa Academy of Science by an authorized editor of UNI ScholarWorks. For more information, please contact scholarworks@uni.edu. RED RocK ZooPLANKTON 73 Copepoda and Cladocera Populations of Red Rock Reservoir, Iowa from April to November, 19701 RONALD L. ASCH2 and PHYLLIS J. KINGSBURY3 RONALD L. AscH and PHYLLIS J. KINGSBURY. Copepoda and Cladocera Populations of Red Rock Reservoir, Iowa from April to November, 1970. Proc. Iowa Acad. Sci., 78(3-4):73-75, 1972. SYNOPSIS. The effects of nutrient renewal, conservation pool water level, and the average weekly discharge rate on the species composition, relative abundance, and population fluctuations of the Copepoda and Cladocera of Red Rock Reservoir were de-termined. The average retention time (flushing rate) was 11.2 days. Twenty-one species were identified with the dominants being Cyclops spp., Diaptomus spp., Daphnia spp., Bosmina longi-rostris, Moina micrura, Ceriodaphnia quadrangula, and Diaphano-Within the last two decades the U.S. Army Corps of En-gineet"s has created some vast changes in the landscape of midwest America. These man-made changes have not only changed the landscape, but have had a definite effect on the ecosystems o'f several streams and major river systems. These changes have included with the State of Iowa, three reser-voirs (Coralville, Red Rock, and Rathbun) completed and SaylorvHle Reservoir currently under construction. The main functions of these structures as stated by the U.S. Army Corps of Engineers are flood control and maintenance of downstream flow during periodsof low water. Each lake or reservoir is an individual problem with its own peculiar chemical, physical, and planktonic characteristics (Schmidt, . 1968) . By selecting stations within a reservoir along the line of water movement it should be po1ssible to show population development. Changes in numbers of indi-viduals of 'various species should indicate changes in popula-tion density. Analysis of the reservoir water level and outlet discharge rate should provide the information to determine flushing rate. Chemical analysis of the water should deter-mine whether nutrient renewal was taking place. lt was the intent of this current study to explain: the species composition, the relative abundance, and some reasons for fluctuations in population abundance of the Copepoda and Cladocera of Red Rock Reservoir. Effects of nutrient renewal, conservation pool water level, and the average weekly dis-charge rate on these zooplankton populations were deter-mined. THE STUDY AREA Red Rock Reservoir, located in south central Iowa, 8 km north of Knoxville, is a U.S. Army Corps of Engineers flood control project on the Des Moines River. Under normal river conditions the conservation pool extends 18.2 km upstream >. 'C.on'tri'oution from the Biology Department of Drake Univer-sity, No. 38. 2 Eureka Senior High School, Eureka, IIL 3 Department of Biology, Drake University. soma spp. Three distinct seasonal peaks in population growth were noted. Population fluctuations showed slight correlation with temperature, transparency, discharge rate, nutrient levels and no relationship was seen with water level. A time interval of 18 to 32 days occurred between high nitrate and phosphate levels and population abundance peaks. Species composition showed distinct seasonal changes. Population numbers began increasing at the dam area and continued upstream with declines following the reverse pattern. INDEX DESCRIPTORS: Zooplankton, Species Composition, Reservoir Flushing. from the dam. The surface of the conservation pool is 221.0 m above· mean sea level. At conservation level the reservoir has a surface of 3,623 ha and an average depth of 3.1 m .. During flood control operations the surface area may in-crease to 26,500 ha with an average depth of 8.1 m and a length of 53.9 km. COLLECTING SITES Three transects were selected to divide 'the conservation pool into approximately three equal parts. Transect one was located through the deep water area, near the dam. Transect two was located near the middle of the reservoir. Transect three was located in the upper end of the reservoir to repre-sent the effects of the entering river. Ten sampling sites were positioned on these transects (Fig. 1). Stations one and two were located on either side of the dam outlet. Stations three, six, and eight were in the old I'iver channel. Station four was positioned in White Breas't Bay on the old creek· channel. rraruooot ) l N Fig. 1. A map showing the location of the stations and transects on Red Rock Reservoir. 1Asch and Kingsbury: Copepoda and Cladocera Populations of Red Rock Reservoir, Iowa frPublished by UNI ScholarWorks, 197174 PRoc. IowA AcAD. Sci. 78 (1971-1972) MATERIALS AND METHODS From April 17 to November 6, 1970, volumetric samples of free swimming zooplankton were collected at weekly inter-vals. Organisms were collected with a three liter Kemmerer water bottle. Samples from each depth were concentrated by emptying the contents into a conical No. 20 mesh plankton net with attached vfaI, preserved in ten percent formalin and returned to the laiboratory for examination. Physical measurements taken at each station included the temperature and a Secchi disc reading. The water samples for chemical analysis were collected bi-weekly by the Iowa State Conservation Department personnel and analyzed by the Iowa State Hygenic Laboratory, Des Moines, Iowa. Water level and discharge rafe data were ob-tained from the Corps of Engineers records. In the fabora:tory the contents of each plankton sample were placed in a gridded plastic petri dish for enumeration and genus identification using a dissecting microscope. Spe-cies determinations were made on representative numbers of each genus (Brooks, 1957, 1959; Pennak, 19'63; Wilson, 1959; and Yeatman, 1959) . PHYSICAL AND CHEMICAL CHARACTERISTICS Water temperatures followed the. seasonal pattern with only weak stratification. The maximum temperature differ-ence within the reservoir was 5.5°C. between the surface and the bottom; this occurred on July 10. Secchi disc reading ranged from 5 to 100 cm. The lowest readings occurred at transect three and at station 4 following a heavy rainstorm. The mean discharge rate calculated for the entire 30 week period was 114.4 m 3 I sec' (Asch, 1971 ) . The calculated reten-tion time varied from 2.58 to 109 days. The average reten-tion time for the 30 week study based on the average dis-charge rate was 11.2 days. The pH values ranged from 7.1 to 8.2 with low values oc-curring during the influx of runoff into the reservoir. Nitrate nitrogen values ranged from 0.2 to 5.6 mg/l and the ortho-phosphate values from 0.1 to 0.9 mg/l. ZOO PLANKTON Since the stations on each transect had similar populations, physical and chemical properties, they were considered as a single unit. Popula'tion fluctuations at station 4, located in White Breast Bay, varied from those in the main reservoir. A gradual increase in zooplankton abundance was noted prior to June 5 (Table 1). The late spring maximum in pop-ulation growth occurred on June 19. A smaller summer peak occurred on transects 2 and 3 on July 17 and transect 1 on July 24. Another minimum was reached on August 14 which was followed by an increase to an early fall peak on Septem-ber 4 ('transect 1) and September 11 (transects 2 and 3). A gradual decrease in abundance was noted from September 18 to the •end of the sampling period. Population abundance at station 4 appeared to peak a:bout the same time as the other stations, but the populations re-mained at high levels for a longer period of time. Twenty-one species were identified. The most abundant forms were Cyclops bicuspidatus thomasi, Diaptomus sici-loides, Daphnia ambigua, Daphnia pulex, Bosmina longiros-tris, Moina micrura, Ceriodaphnia quadrangula, and Diapha-TABLE 1 The Average Number of Copepoda and Cladocera Collected per Liter at Each Transect and Station Four. Date Trans. I Trans. 2 Trans. 3 Sta. 4 4/17 1.7 1.3 1.3 4.7 4/24 3.8 0.6 0.5 3.0 5/1 7.5 1.3 0.7 4.9 5/8 2.1 0.6 1.3 2.2 5/15 4.2 0.4 0.2 1.3 5/22 7.3 1.7 1.2 9.1 5/28 6.2 4.8 1.8 39.1 6/5 16.0 6.8 0.7 36.l 6/12 43.5 18.7 6.5 22.4 6/19 79.9 22.3 44.9 50.5 6/26 33.6 10.7 5.4 17.6 7/2 7.1 17.7 11.9 40.9 7/10 12.4 20.l 9.8 23.2 7/17 19.2 24.9 18.7 19.l 7/24 56.7 8.0 5.1 28.5 7/31 19.1 15.5 7.2 27.9 8/7 18 . .1 17.6 14.1 21.2 8/14 11.4 3.2 2.8 5.5 8/21 21.0 15.2 4.7 11.4 8/28 27.6 19.2 10.5 13.6 9/4 42.6 25.3 14.7 27.2 9/11 33.2 39.l 15.2 31.6 9/18 28.3 10.8 4.8 21.0 9/25 28.9 10.3 4.6 14.l 10/2 19.2 7.4 2.6 16.3 10/9 18.l 9.4 2.9 4.8 10/16 6.1 2.8 0.9 8.2 10/23 7.2 2.4 1.1 5.9 10/30 2.4 1.9 0.7 2.7 11/6 1.3 0.7 0.2 0.8 nosoma brachyurum. The remaining species occuned in small numbers, except Cyclops varicans rubellus which was quite common during August and September. DISCUSSION Multiple Regression Analysis Correlation for temperature ahd the seven most abundant genera indicated that there might be a general, direct rela-tionship between temperature and Cyclops and Moina, while Diaptomus, Bosmina and Diaphanosoma showed a slight re-lationship. Secchi disc readings and genera populations showed a gen-eral relationship with Cyclops, Moina and Daphnia popula-tions. A general inverse correlation was found between tur-bidity and Cyclops and Bosmina. The correlation values between nitrate nitrogen and popu-lations showed an inverse correlation with Diaptomus, Cerio-daphnia and Diaphanosoma. Phosphate levels showed an in-verse correlation with Moina. Diaptomus and Diaphanosoma showed the greatest inverse relationship to water discharge, while Daphnia, Moina and Ceriodaphnia showed a slight inverse relationship. Water level showed no correlation with population number at any transect or station(Asch, 1971). A time interval occurred between the nutrient (nitrate and phosphate) levels and the population abundance peaks. The highest levels of nutrients occurred on June 1 and were fol-lowed 18 days later by the late spring population maximum. The summer population peak was not preceded by a nutrient 2Proceedings of the Iowa Academy of Science, Vol. 78 [1971], No. 3, Art. 13https://scholarworks.uni.edu/pias/vol78/iss3/13RED RoCK ZooPLANKTON 75 increase, but the nitrate and phosphate levels were high. The fall population pulse was preceded by an increase in nitrate levels (August 24) and phosphate levels (August 11). The populations peaks on transect 3 var±ed from those on transect 1 and 2 by the number of days elapsing since the nutrient increases. There was a lag of 19 to 32 days between nutri-ent level increases and the population peaks. Species Composition There was a seasonal change in the species composition at all stations. In April, C. bicuspidatus thomasi, Diaptomus clavipes, D. siciloides, Daphnia ambigua, D. pulex, and Bos-mina longirostris were present. D. clavipes disappeared in late April. During June, two new species, Moina micrura and Diaphanosoma brachyurum appeared. In July, D. ambigua disappeared. In August, Cyclops varica.ns rubellus and Para-cyclops fimbriatus poppei were present. During September, the predominant species were D. siciloides and D. brachyur-um. In September, M. micrura disappeared and Ceriodaph-nia quadrangula appeared. In October, D. pulex and D. brachyurum were the abundant species. During the first week in November, five species were present: C. bicuspidatus thomasi, D. siciloides, D. pulex, B. longirostris, and Diapha-nosoma leuchtenbergia.num. Population numbers of a species began to increase first at transect 1, then succeeding increases were shown at trans-ects 2 and 3. The population numbers of a given species de-clined first in the upper end of the reservoir (transect 3), while persisting for a longer period of time at the dam area (transect 1) . Similar patterns of zooplankton distribution were noted in Lewis and Clark Lake, South Dakota (Cowell, 1970, Tash, Swanson, and Siefert, 1966). ACKNOWLEDGMENT The authors wish to express their gratitude to James Mayhew, of the Iowa State Conservation Commission, who was kind enough to cooperate in gathering the data for this study. · LITERATURE CITED AscH, RONALD L. 1971. Copepoda and cladocera populations of Red Rock Reservoir, Iowa from April to November, 1970:. Un-published M.A. thesis, Drake University Library. BROOKS, J. L. 1957. The systematics of North American Daphnia. Conn. Acad. Arts and Sci., 13:1-180. ____ . 1959. Cladocera. In: W. T. Edmondson (ed.), Fresh-water biology (2nd ed.). John Wiley and Sons, New York. pp. 587-656. COWELL, B. C. 1970. The influence of plankton discharges from an upstream reservoir on standing crops in a Missouri River Reservoir. Limnol. Oceangr., 15( 3) :427-441. PENNAK, R. W. 1963. Species identification of the fresh-water cyclopoid Copepoda of the United States. Amer. Microscop. Soc. Trans., 82( 4) :353-359. SCHMIDT, D. J. 1968. Plankton of a variable level flood control reservoir. Proc. Iowa Acad. Sci., 75:48-54. TASH, J. C., G. A. SWANSON & R. E. SIEFERT. 1966. A report on the occurrence and distribution of Cladocera and Copepoda in Lewis and Clark Lake, South Dakota. Univ. Kans. Sci. Bull., 46( 11) :425-432. WILSON, M. S. 1959. Calanoida. In: W. T. Edmondson (ed.), Fresh-water biology (2nd ed.). John Wiley and Sons, New York. pp. 738-794. YEATMAN, H. C. 1959. Cyclopodia. In: W. T. Edmondson (ed.), Fresh-water biology (2nd ed.). John Wiley and Sons, New York. pp. 795-815. 3Asch and Kingsbury: Copepoda and Cladocera Populations of Red Rock Reservoir, Iowa frPublished by UNI ScholarWorks, 1971

Copepoda and Cladocera Populations of Red Rock Reservoir, Iowa from April to November, 1970

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Copepoda and Cladocera Populations of Red Rock Reservoir, Iowa from April to November, 1970

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