Common Plankton of Twin Lakes, Colorado

REC-ERC-82-21

COMMON PLANKTON OF TWIN LAKES, COLORADO

February 1983

Engineering and Research Center

U. S. Department of the Interior Bureau of Reclamation 7-2090 ( 4-81) Water and Power TECHNICAL REPORT STANDARD TITLE PAGE 1. REPORT NO. 2. GOVERNMENT ACCESSION NO. 3. RECIPIENT'S CATALOG NO. REC-ERC-82-21

4. TITLE AND SUBTITLE 5. REPORT DATE February 1983 Common Plankton of Twin Lakes, Colorado 6. PERFORMING ORGANIZATION CODE

7. AUTHOR(S■ 8 , PERFORMING ORGANIZATION REPORT NO. Davine M. Lieberman REC-ERC-82-21

9. PERFORMING ORGANIZATION NAME AND ADDRESS 1 0. WORK UNIT NO.

Engineering and Research Center 11. CONTRACT OR GRANT NO Bureau of Reclamation Denver, Colorado 80225 1 3. TYPE OF REPORT AND PERIOD COVERED 12. SPONSORING AGENCY NAME AND ADDRESS

Engineering and Research Center Bureau of Reclamation Denver, Colorado 80225 1 4. SPONSORING AGENCY CODE DIBR

1 5. SUPPLEMENTARY NOTES Microfiche or hard copy available at the Engineering and Research Center, Denver, Colo. Ed:REC

1 6. ABSTRACT

ABSTRACT - A series of studies is being performed to evaluate the effects of the Mt. Elbert Pumped-Storage Powerplant on the ecology of Twin Lakes. Twin Lakes are a pair of connected dimictic lakes, formed as the result of glacial action on alluvial deposits. This report presents a taxonomic species study of the common plankton collected since 1974 from Twin Lakes. A total of 11 zooplankters and 14 phytoplankters were identified from the limnetic zone of Twin Lakes and the associated Mt. Elbert Forebay. The four divisions of zooplankton included four species of Rotifera (rotifer), three species of Copepoda (copepod), three species of Cladocera (cladoceran), and one species of Mysidacea (opossum shrimp). The dominant zooplankters were the rotifers and copepods. The nocturnal opossum shrimp, Mysis relicta are abundant in Twin Lakes but were not collected in plankton samples. Cladocerans were rarely collected and made up less than 1 percent of the zooplankton population. The lower lake has a greater density of zooplankton than the upper lake. For example, in July 1981, average zooplankton densities in the lower lake reached a maximum of 116 individuals/L, as compared to 53 individuals/L in the upper lake. The four divisions of phytoplankton included three species of Chrysophyta (blue-green algae), three species of Chlorophyta (green algae), six species of Bacillariophyta (diatom), and two species of Cyanophyta (yellow-brown algae). The phytoplankton was dominated by the yellow-brown algae, Dinobryon, and by the diatoms, Aster/one//a and Synedra. During 1981, average density of phytoplankton reached a maximum of 4870 organisms/L during September in the upper lake; the average density in the lower lake peaked during March at 18,042 organisms/L.

1 7. KEY WORDS AND DOCUMENT ANALYSIS a. DESCRIPTORS-- /*phytoplankton/* zooplankton/* taxonomy/ limnology/ lakes/ shrimp/ cladocera/ copepods/ rotifers/ blue-green algae/ green algae/ diatoms/ yellow-brown algae/ algae/ power plants/ aquatic environment/ pumped storage/ fauna/ flora/ systematics

b. IDENTIFIERS-- / Twin Lakes, Colo./ Mt. Elbert Pumped-Storage Powerplant, Colorado

c. COSATI Field/Group 06H coviR R : 0606 SRIM

1 8. DISTRIBUTION STATEMENT 1 9. SECURITY C LASS 21. NO. OF PAGES (THIS REPORT) Available from the National Technical Information Service, Operations UNCLASSIFIED 17 Division, 5285 Rood, Springfield, Virginia 22/61. Port Royal 20. SECURITY CLASS 22. PRICE THIS PAGE/ UNCLASSIFIED REC-ERC-82-21

COMMON PLANKTON OF TWIN LAKES, COLORADO

by Davine M. Lieberman

February 1983

Applied Sciences Branch Div ision of Research Engineering and Research Center Denver, Colorado SI METRIC

UNITED STATES DEPARTMENT OF THE INTERIOR BUREAU OF RECLAMATION ACKNOWLEDGMENTS

This study is a part of the Twin Lakes Ecological study (DR-331). Twin Lakes studies are being performed under the supervision of N.E. Otto, Environmental Sciences Section; and L.O. Timblin, Jr., Applied Sciences Branch. Contributions to both the field and laboratory portions of this study by the Aquatic Ecology Group are gratefully acknowledged. Special thanks to Richard Roline, biologist, for his assistance and hours spent in species identification of plankton.

The research covered by this report was funded by the Frying- pan-Arkansas Project DR331, Lower Missouri Region, Division of Research, Bureau of Reclamation.

As the Nation's principal conservation agency, the Department of the Interior has responsibility for most of our nationally owned public lands and natural resources. This includes fostering the wisest use of our land and water resources, protecting our fish and wildlife, preser- ving the environmental and cultural values of our national parks and historical places, and providing for the enjoyment of life through outdoor recreation. The Department assesses our energy and mineral resources and works to assure that their development is in the best interests of all our people. The Department also has a major responsibility for American Indian reservation communities and for people who live in Island Territories under U.S. Administration.

The information contained in this report regarding commercial products or firms may not be used for advertising or promotional purposes and is not to be construed as an endorsement of any product or firm by the Bureau of Reclamation. CONTENTS

Page

Introduction ...... 1 Methods ...... 2 Results and discussion ...... 2 Zooplankton ...... 2 Zooplankton abundance ...... 3 Phytoplankton ...... 7 Phytoplankton abundance ...... 7 Summary ...... 12 Glossary of terms ...... 13 Bibliography ...... 14 Appendix ...... 15

TABLES

1 Zooplankton collected from Twin Lakes 1974-82 ...... 3 2 Phytoplankton collected and identified at Twin Lakes ...... 7 3 Twin Lakes Phytoplankton ...... 16

FIGURES

1 General location map of Twin Lakes, Colo...... 1 2 Twin Lakes and Mt. Elbert Forebay ...... 1 3a Structure of Daphnia ...... 4 3b Claw of D. pulex ...... 4 3c Claw of D. rosea ...... 4 4 Daphnia pulex. Teeth of pecten of postabdominal claw ...... 5 5 Structure of Bosmina ...... 5 6a Structure of Cyclops ...... 6 6b Leg 4 ...... 6 7 Cyclops bicuspidatus thomasi: Leg 5 ...... 6 8 Cyclops bicuspidatus thomasi. Caudal ramus ...... 6 9 Cyclops bicuspidatus thomasi Leg 4 ...... 7 10a Structure of Diaptomus ...... 8 10b Antepenultimate segment ...... 8 10c Leg 5 of D. judayi ...... 8 10d Leg 5 of D. connexus ...... 8 11 Diaptomus judayi Right antenna ...... 9 12 Diaptomus judayi Right Leg 5 ...... 9 13a Structure of Kellicottia ...... 9 13b Structure of Keratella ...... 9 14 Species composition of zooplankton population in Twin Lakes during 1981 ...... 10 15 Species composition of phytoplankton population in Twin Lakes during 1981 ...... 11 INTRODUCTION Mt. Elbert Pumped-Storage Powerplant located on the northwest shore of the lower lake has been operating sporadically since mid-1981. A newly Twin Lakes are a pair of connected dimictic lakes constructed dam on the shallow eastern end of located on Lake Creek, a tributary to the Arkansas the lower lake, which will raise the water level River, on the eastern slope of the Continental and allow mixing of the two lakes to increase, will Divide (figs. 1 and 2). The lakes are natural and begin to be used in 1984. Detailed information on formed as the result of glacial action on alluvial the limnology and ecology of Twin Lakes is in deposits (Buckles, 1973) [2].1 The lower lake is the LaBounty and Sartoris (1981) [8], LaBounty, et al. largest natural mountain lake in Colorado (Pennak, (1980) [9]; Sartoris, et al. (1977) [15]; and La- 1 966) [13]. Bounty and Sartoris (1980) [7]. In 1901, the Twin Lakes Reservoir Company built a dam on the Lake Creek outlet. The dam and the dredging of the connecting channel allowed for water level fluctuations of 7.8 m in the lower lake and about 5.8 m in the upper. The lakes' water surface elevation is 2802 m above mean sea level. The maximum depth in the lower lake is about 27 m, and about 28 m in the upper lake. The lakes are currently operated as a reservoir.

The present studies of the ecology of Twin Lakes began in 1971. The overall purpose of these studies is to identify the effects of operating the pumped-storage powerplant on Twin Lakes. The

Figure 1.—General location map of Twin Lakes, 1 Numbers in brackets refer to entries in the Bibliography. Colorado.

Mt. Elbert Conduit (buried) u_ from Turquoise Reservoir

Mt. Elbert Forebay Dam

Forebay Inlet-Outlet Dike LEGEND Inlet-Outlet Structure — Preproject shoreline Penstocks (buried) New shoreline Mt. Elbert Pumped-Storage Powerplant Research sampling station

Flow ICO 0 1000 Twin Lakes SCALE OF METERS Dam (new) Cie

°44 4 March 13. 1982 Figure 2.—Twin Lakes and Mt. Elbert Forebay. Previous to this study, both phytoplankton and Identification was done at this step. The following zooplankton from Twin Lakes had been enu- references were used in the identification of Twin merated and identified to genus. In 1976, the first Lakes plankton: Palmer (1959) [11]; Needham and comprehensive species list of the phytoplankton Needham (1962) [10]; Ward and Whipple (1966) was prepared by Claire Norton, a botanist formerly [16]; Pennak (1978) [12]; Dumont and Green of Colorado State University, Fort Collins. Little (1980) [4]; and Dodson (1981) [3]. recent work on the identification of zooplankton to species has been done at Twin Lakes. However, Subsamples from plankton collections made from Reed and Olive (1958) [14], in their study of the Twin Lakes since 1974 were randomly examined effect of altitude on the distribution of small for species identification of zooplankton only. In crustaceans in Colorado, included a list of species the process, two photographic techniques were found at Twin Lakes. This list is presently outdated used. To examine the fine detail of the anatomical and incomplete. parts, a Polaroid 545 Land Camera mounted on top of a Leitz Wetzler Ortholux Compound light This study provides a list of the common plankton microscope was used. Magnifications of 100x and collected from Twin Lakes and the Mt. Elbert 400x were used in photographing these parts. A Forebay through 1981 and continuing in to 1982. second photographic approach was to take photo- Descriptions of the major species of rotifers, graphs through the ocular of a binocular dissecting copepods, and cladocerans are included. A glos- microscope with a 35-mm Nikon camera. This sary of common terms used is found at the back of technique generally resulted in poor photographs this report. due to the inadequate lighting, even though several photographs of each specimen were taken to bracket the exposure.

METHODS RESULTS AND DISCUSSION Plankton samples were collected at regular inter- vals from two locations in Twin Lakes, one in the Zooplankton upper and the other in the lower lake. Sampling of the Mt. Elbert Forebay began in fall 1981. From Four kinds of zooplankters were found in the 1971 to 1974, sampling was carried out on an samples of plankton from Twin Lakes: opossum irregular basis. Since May 1974, field surveys shrimp, cladocerans, copepods, and rotifers. At have usually been conducted monthly throughout Twin Lakes around the turn of the century, Juday the winter months and biweekly during the sum- (1906) [6] found a much more diverse zooplankton mer months. fauna; 6 species of rotifers, 5 species of copepods, and 10 species of cladocerans. In recent years, During the early years of this study, sampling was only three species of cladocerans have been done with a No. 20 Wisconsin net (mesh opening collected, most of which were found only in the = 0.076 mm) and a No. 10 metered Clarke- Mt. Elbert Forebay. Cladocerans are only collected Bumpus plankton sampler (mesh opening = 0.158 occasionally from Twin Lakes themselves. Low mm). After 1977, a No. 20 closing net (mesh numbers of cladocerans are probably due to opening = 0.076 mm) and bucket were used for predation by the opossum shrimp, Mysis relicta, vertical hauls. Replicate hauls were taken with which was introduced into Twin Lakes in 1958 the closing net from depths of 0 to 5,5 to 10, 10 to (Goldman, et al., 1979) [5]. The species listed in 15, and 15 to 20 m, or the bottom. Eight samples table 1 represent those zooplankters identified from the upper and lower lakes and six samples from Twin Lakes since 1974. A brief description from the Mt. Elbert Forebay were collected during summarizes the important characteristics of each survey. A 2-percent formalin solution was species examined for this study. Polyarthra sp. used to preserve the samples. Laboratory analysis and Brachionus sp. were not keyed to species of the samples consisted of plankton identification because specific parts of the organisms could not and enumeration. Six subsamples from each be identified under the light compound micro- plankton collection were taken. Three of these scope. subsamples of 1 mL each were pipetted onto Sedgwick-Rafter counting cells for identification Division: Cladocera of zooplankters. The other three subsamples of 1 /10 mL each were pipetted onto Palmer counting Daphnia pulex Leydig (fig. 3a). — Head longest cells for identification of phytoplankton to genera. near midline; teeth of middle pecten of post- The next step was to identify plankton to species. abdominal claw stout, the longest at least three

2 Table 1. — Zooplankton collected from Twin in Twin Lakes. Found in upper lake, lower lake, Lakes, 1974-82 and Mt. Elbert Forebay.

Division: Cladocera Diaptomus judayiMarsh (fig. 10a). —Antepenulti- mate segment of male right antenna with a * Daphnia pulex Leydig slender blunt process (figs. 10b, 11); inner margin * Daphnia rosea Sars of right fifth exopod bearing a triangular hyaline * Bosmina longirostris (Mueller) lamella, 0.9 mm long (figs. 10c, 12). Found in lower lake, upper lake, and Mt. Elbert Forebay. Division: Copepoda Diaptomus connexus Light. — Antepenultimate * Diaptomus judayi Marsh segment of male right antenna with a slender * Diaptomus connexus Light blunt process; first segment of male right fifth * Cyclops bicuspidatus thomasi Forbes exopod produced as a rounded lobe of its lateral distal margin, its inner margin bearing a rounded Division: Rotifera hyaline lamella, 0.9 to 1.5 mm long (fig. 10d). Found in lower lake, upper lake, and Mt. Elbert * Kellicottia longispina 0 hlstrom Forebay. * Keratella cochlearis Bry de St. Vincent Polyarthra sp. Division: Rotatoria Brachionus sp. Kellicottia longispina Ohlstrom (fig. 13a). — One Division: Mysidacea very long posterior spine and six anterior spines, three of which are very long, 0.46 to 0.73 mm Mysis relicta Loven long. Found in lower lake, upper lake, and Mt. Elbert Forebay.

* Organisms examined for species identification. Keratella cochlearis Bry de St. Vincent (fig. 13b). — Dorsal surface of lorica with a pattern of times as long as teeth of distal pecten (figs. 3b, 4); polygonal facets. One posterior spine, and with up to 2.5 mm long. Found in Mt. Elbert Forebay. six short to medium anterior spines, 0.13 to 0.15 Rare in the lower lake and has not been found in mm long. Found in lower lake, upper lake, and Mt. the upper lake. Elbert Forebay.

Daphnia rosea Sars. — Head twice as deep as Zooplankton Abundance long; teeth of all three pectens of claw about the same size (fig. 3c); up to 2 mm long. Found in Mt. Rotifers, mysids, copepods, and cladocerans were Elbert Forebay. Rare in lower lake and has not found in the plankton samples from Twin Lakes. been found in the upper lake. Rotifers were the most abundant, followed by copepods and an occasional cladoceran. Clado- Bosmina longirostris (o.f.m.) (fig. 5). — Female cerans made up less than 1 percent of the postabdominal claw with a very fine distal pecten; zooplankton population. Opossum shrimp, Mysis frontal sensory bristle near midpoint between eye relicta, are very abundant in Twin Lakes but are and tip of rostrum, up to 0.6 mm. Found in upper not common in plankton samples since they are lake, lower lake, and Mt. Elbert Forebay. nocturnal and only distributed in the water column at night. Zooplankton for this study was collected in daylight hours and, consequently, few mysids Division: Copepoda were found in the plankton samples. Other sampling procedures were used to collect mysids Cyclops bicuspidatus thomasi Forbes (fig. 6). — (Bergersen and Maiolie, 1981) [1]. Figure 14 First antenna 17-segmented; terminal segment of contains zooplankton relative abundance data for fifth leg with a seta and a short spine or spur that each of the Twin Lakes during 1981. is always half or more than the length of the segment (fig. 7); lateral seta of caudal ramus The lower lake has a greater density of zooplankton attached at a point two-thirds or less the distance than the upper lake. In the summer months, June from the base to the end of ramus (fig. 8); inner through September, the average total density of terminal spine of endopod of fourth leg about one- zooplankton is greater than during other months half the length of the outer terminal spine, 0.9 to of the year. During 1981, average zooplankton 1.2 mm (figs. 6b, 9). The most abundant copepod densities in the lower lake ranged from a high of

3 --- HEAD

--COMPOUND EYE

--FIRST ANTENNA

_SECOND ANTENNA

PECTEN OF CLAW

\ POSTABDOMEN

(a)

(c)

Figure 3.—a. Structure of Daphnia. b. Claw of D. pulex. Teeth of middle pecten at least three times as long as teeth of distal pecten. c. Claw of D. rosea. Teeth of all three pectens of claw about the same size.

4 116 individuals/L in July to a low of 16.5 individuals/L in September. Average density in the upper lake ranged from a high of 53 individuals/L in July to a low of 5.2 individuals/L in June. Throughout the year, rotifers and copepods comprised 99 percent of the total zooplankton population. The most abundant zooplankters during the month ofJ uly were the rotifers. Rotifers comprised 83 and 78 percent of the total zooplankton population in lower and upper Twin Lakes, respectively. The dominant and most abundant rotifer species is Keratella cochlearis, followed by Kellicottia longispina and Polyarthra sp. The population of K. cochlearis is greatest from July to November with a peak in numbers occurring in July. Brachionus sp. is found in greatest abundance during the months of October, November, and December, but it is not as abundant as the other three species mentioned.

Copepods are dominated by three species: Cyclops bicuspidatus thomasi, Diaptomus judayi, and Diaptomus connexus. Diaptomus is more abun- Figure 4. —Daphnia pulex. dant from February to June than from June to Teeth of pecten of postabdominal claw. 400x (magnification). Photo January. Cyclops bicuspidatus thomasi, the domi- P801-D-80118. nant copepod, appears throughout the year with

ANTENNULES

EYE

SENSORY, BRISTLE-

ROSTRUM

\PECTEN

CLAW

Figure 5.—Structure of Bosmina.

5 CAUDAL RAMUS

FIRST ANTENNA

-_FOURTH LEG __SPINES (a)

(b)

Figure 6.—a. Structure of Cyclops. b. Leg 4. Inner terminal spine of endopod about one-half the length of the outer terminal spine.

Figure 7.--Cyclops bicuspidatus thomasi Leg 5. Figure 8.—Cyclops bicuspidatus thomasi Caudal 400x (magnification). P801-D-80119. ramus. 400x (magnification). P801-D-80120.

6 Table 2. —Phytoplankton collected and identified at Twin Lakes.* Division: Chrysophyta (yellow-green or yellow- brown algae)

Dinobryon cylindricum I mhof Mallomonas elongata Rever. Mallomonas pseudocoronata Prescott

Division: Chlorophyta (green algae)

Dictyosphaerium pulchellum Wood Sphaerocystis schroeteri Chodat Staurastrum longiradiatum W. &W.

Division: Bacillariophyta (diatom)

Aster/one/la formosa Hassall Synedra amphicephala Kuetz Synedra delicatissima W. Sm. Synedra radians Kuetz Synedra ulna var. danica (Kuetz) VH Figure 9.—Cyclops bicuspidatus thomasi Leg 4. Tabellaria flocculosa (Roth) Ku etz 400x (magnification). P801-D-80121. Division: Cyanophyta (blue-green algae) numbers increasing from June to January con- Oscillatoria amphibia C.A. Agardh comitant with a decrease in numbers of Diap- Oscillatoria ten/us C.A. Agardh tornus. * Based on a more complete list by Claire Norton. Cladocerans are rarely collected from Twin Lakes but occasionally are found in the Mt. Elbert Forebay. The origin of Daphnia in the forebay is nutrient inflow for a particular year (LaBounty and either autochthonous or imported from Turquoise Sartoris, 1980) [7]. The average density of phyto- Reservoir, where they are abundant, through the plankton is greater in the lower lake than in the Mt. Elbert conduit (fig. 2). Daphnia pulex and upper lake. Phytoplankton populations in the Daphnia rosea are both collected from the forebay. lower lake peak in the spring months and de- The only cladoceran found in the upper and lower crease in the summer months. For example, in lake and the forebay is the Bosmina. Bosmina 1 981 average phytoplankton density in the lower longirostris is collected infrequently. In fact, lake reached a yearly high of 18 042 organisms/L cladocerans usually make up less than 1 percent in early March (fig. 15). The 1981 yearly low of of the total population of zooplankters. Further 1 84 organisms/L occurred in early September. data on zooplankton abundances are in LaBounty and Sartoris, 1981 [8], and LaBounty, et al., 1980 Peak phytoplankton density in the upper lake is [9]. generally in late summer or early fall. For example, in 1 981 average density ranged from a high of Phytoplankton 4870 organisms/L in early September to a low of 704 organisms/L in late September. The peak An unpublished list of the phytoplankton, which density in the upper lake occurred in early included 50 species (appendix), was provided in September, the same period in which the average 1 976 by Claire Norton. Norton sampled both the total phytoplankton of the lower lake reached the limnetic and littoral zones of Twin Lakes. A list of yearly low. commonly occurring limnetic phytoplankters, based on Norton's identifications, is in table 2. The upper and lower lakes and the Mt. Elbert Forebay are typically dominated by the yellow- Phytoplankton Abundance brown alga, Dinobryon cylindricum, and by the diatom, Aster/one/la formosa, and four species of Phytoplankton densities and species composition Synedra. For example, in 1981 the lower lake was in Twin Lakes depends on runoff and the resulting dominated by the species Synedra spp. from

7 ANTENNA

ANTEPENULTIMATE SEGMENT

(a)

1111 r _ _SLENDER PROCESS 7 'AL TRIANGULAR _ ROUNDED HYALINE LAMELLK HYALINE LAMELLA —

— —AN TEPEN ULTIMATE SEGMENT _ CLAW (b) (c) (d) CLAW

Figure 10.— a. Structure of Diaptomus. b. Antepenultimate segment of male right antenna showing slender blunt process. c. Leg. 5 of D. judayi. Inner margin of right exopod bearing a triangular hyaline lamella. d. Leg. 5 of D. connexus. Inner margin bearing a rounded hyaline lamella.

January to March and again from May to Sep- lomonas spp., the diatom Tabellaria sp., and the tember. Peak density ofAsterionnella sp. occurred green algae species Dictyosphaerium are not in April, and Dinobryon sp. reached highs in found or are found infrequently, possibly because September and October. The most abundant of limited nutrient loading during the spring species in the lower lake was Synedra spp. In the runoff. In 1981, blue greens were nearly absent upper lake during 1981, Dinobyron sp. was the from the phytoplankton population, while in 1980, most abundant species. Aster/one/la sp. occurred both Mallomonas spp. and Dictyosphaerium sp. in abundance only in April. Synedra spp., although were quite abundant. present throughout the year, was never abundant in the upper lake during 1981.

There are years when the blue-green species 2 J.F. LaBounty, et al., 1981 Yearly Report of Findings at Oscillatoria spp., the golden-brown species Mal- Twin Lakes, Colorado, unpublished.

Figure 11.—Diaptomus judayi. Right antenna. Figure 1 2.—Diaptomus judayi. Right leg 5 Antepenultimate segment posses- Triangular hyaline lamella. 400x (magnifica- ses slender blunt process. 400x (magn ification). tion). P801-0-80123. P801-0-80122.

POSTERIOR SPINE

(a) ANTERIOR SPINE

POSTERIOR SPINE

(b) POLYGONAL FACETS ANTERIOR SPINE

Figure 13.— a. Structure of Kellicottia. b. Structure of Keratella.

9 BOSMINA ROTIFERS NAUPLI1 DIAPTOMUS CYCLOPS LOWER LAKE 100

PERCENT COMPOSITION 25

JAN MAR MAY JUL SEP NOV 19 81

UPPER LAKE 100

(.71 0 a_ o 50

1 1 JAN MAR MAY JUL SEP NOV 19 81 ZOOPLANKTON

Figure 14.—Species Composition of Zooplankton Population in Twin Lakes during 1981.

10 DICTOSPH A ERI UM AND SPHAEROCYST IS DIN OBRYON SYNEDRA ASTER ION EL LA LOWER LAKE 1 00 -Sr 4.4P1117,

PERCENT COMPOSITION 25

1 JAN MAR MAY JUL SEP NOV 19 81

UPPER LAKE 100

50 PERCENT COMPOSITION 25

1 9 81 PHYTOPLANKTON

Figure 15.—Species Composition of Phytoplankton Population in Twin Lakes during 1981.

11 The green alga Sphaerocystis sp. and the desm id 2. The zooplankton population in Twin Lakes is Staurastrum sp. are rare in both the lower and dominated by the rotifers and copepods. Keratella upper lakes. LaBounty and Sartoris (1980) [8] cochlearis and Kellicottia longispina are the two found distinct fluctuations in phytoplankton abun- most abundant rotifer species, and Cyclops bi- dance from year to year. cuspidatus thomasi is the dominant copepod species. Cladocerans are rare in Twin Lakes because of the predaceous freshwater shrimp Mysis relicta. SUMMARY 3. The dominant genera of phytoplankton in Twin Lakes are Asterionella, Synedra, and Dinobryon. 1. Plankton samples collected from 1974 to 1982 Each species is abundant at a different time of the were randomly sampled for species identification. year and occurs in greater numbers in the lower A total of 11 zooplankters and 14 phytoplankters lake than in the upper lake. The densities of were identified from the limnetic zones of Twin Oscillator/a, Mallomonas, Tabellaria, and Dic- Lakes and the associated Mt. Elbert Forebay. tyosphaerium fluctuate from year to year.

12 GLOSSARY OF TERMS

1. Antepenultimate: Third last, such as the third 10. Lorica: Enveloping rigid case or secreted last segment of a Diaptomus antenna. exoskeleton in invertebrates as in many rotifers.

2. Anterior: Of, pertaining to, or toward front 11. Pecten: Any comb-like structure. end. 12. Polygonal facets: A six-sided pattern on dorsal 3. Caudal ramus: Collectively, the two terminal side of lorica on Keratella. processes on the last abdominal segment in copepods. 13. Postabdomen: Posterior end of the cladocera body, bears a pair of terminal claws and is usually 4. Claw: Hook-like structure with spines and bent so as to extend ventrally or anteriorly. teeth of various sizes and arrangements on the concave side. 14. Posterior: Of or pertaining to rear end. 5. Dimictic: Lakes having two mixing periods. Overturns occur each year in the spring and fall. 15. Rostrum: Any snout-like prolongation of the head. 6. Distal: Situated away from base or point of attachment. 16. Sensory bristle: Any short, stiff hair or hair- like projection which is associated with reactions 7. Dorsal: Of or pertaining to back or upper to stimuli on a cladocera. surface. 17. Seta: Bristles or hairs of invertebrates. 8. Endopod and Exopod: Typical copepod appendage; consists of a short basal two-segmented 18. Slender blunt process: A blunt projection on a portion, a median branch (endopodite), and a later- copepoda antenna. al branch (exopodite); each of the two branches (rami) is segmented and of varying size. 19. Spine: A stiff, pointed, external process or appendage. 9. Hyaline Lamella: Clear, translucent thin plate-like structure. 20. Terminal: End or last.

13 BIBLIOGRAPHY

[1] Bergerson, E. P., and M. A. Maiolie, "Twin Colorado: 1 980 Report of Findings," Bureau Lakes Investigations — Entrainment Phase I of Reclamation Report No. REC-ERC-82-7, — Testing: 1 981 Annual Progress Report," Denver, Colorado, 56 pp., 1981. Colorado Cooperative Fishery Research Unit, USBR (Bureau of Reclamation) Contract No. [9] LaBounty, J. F., J. J. Sartoris, S. G. Campbell, 7-07-83-V0700, pp. 1 8-27, Fort Collins, J. R. Boehmke, and R. A. Roline, "Studies of Colorado, 1 981. the Effects of Operating the Mt. Elbert Pumped-Storage Powerplant on Twin Lakes, [2] Buckles, W. G., "Archaeological Salvage for Colorado: 1 979 Report of Findings," Bureau the Fryingpan-Arkansas Project in Lake, of Reclamation Report No. REC-ERC-80-7, Chaffee and Pitkin Counties, Colorado in Denver, Colorado, 32 pp., 1 980. 1 972," National Park Service, Contract No. 2-929-P-20073, Anthropology Lab., So. Needham, J. G., and P. R. Needham, A Colo. State College, Pueblo, 1 57 pp., 1 973. Guide to the Study of Freshwater Biology, San Francisco, California, 1 08 pp., 1 962. [3] Dodson, S. I., "Morphological Variation of Daphina pulex Leydig (Crustacea:Cladocera) Palmer, C. M., Algae in Water Supplies, U.S. and Related Species From North America," Department of Health, Education and Wel- In: Hydrobiologia, vol. 83, pp. 1 01-114, fare, Publication No. 657, 88 pp., 1959. 1 981. Pennak, R. W., Freshwater Invertebrates of [4] Dumont, H. J., and J. Green, editors, "Rota- the United States, 2nd edition, New York, toria," Proceedings of the 2nd International 803 pp., 1 978. Rotifer Symposium, Gent, Belgium, Septem- ber 17-21, 1979, Hydrobiologia, vol. 73 (1- Pennak, R. W., "Rocky Mountain States," In: 3), 263 pp., 1 980. D. G. Frey, Limnology in North America, University of Wisconsin Press, Madison, [5] Goldman, C. R., M. D. Morgan, S. T. Threl- Wisconsin, pp. 349-369, 1966. keld, and N. Angeli, "A Population Dynamics Analysis of Cladoceran Disappearance From [14] Reed, E. B., and J. R. Olive, "Altitudinal Lake Tahoe, Ca liforn ia-N evada,"Limnology Distribution of Some Entomostraca in Colo- and Oceanography, vol. 24, No. 2, pp. 297- rado," In: Ecology, vol. 39, No. 1, pp. 66-74, 298, 1 979. 1 958. [6] Juday, C., "A Study of Twin Lakes, Colorado, [15] Sartoris, J. J., J. F. LaBounty, and H. D. With Special Consideration of the Food of Newkirk, "Historical, Physical, and Chemi- the Trouts," Bureau of Fisheries Document cal Limnology of Twin Lakes, Colorado," No. 616, pp. 1 51-178, 1906. Water and Power Resources Service, REC- ERC-77-13, Denver, Colorado, 88 pp., 1 977. [7] LaBounty, J. F., a nd J. J. Sartoris, "Effects of Drought on Colorado and Wyoming Im- [16] Ward, H. B., and G. C. Whipple, Freshwater poundments," Proceedings of the Sympo- Biology, New York, 1 248 pp., 1966. sium on Surface-Water Impoundments, Minneapolis, Minnesota, June 2-5, 1980. "Note: From November 1979 to May 1 981, the [8] LaBounty, J. F., and J. J. Sartoris, "Studies Bureau of Reclamation was known as the Water of the Effects of Operating the Mt. Elbert and Power Resources Service; consider the Pumped-Storage Powerplant on Twin Lakes, names synonymous in this Bibliography."

14 APPENDIX

TWIN LAKES PHYTOPLANKTON Eunotia sp. [pectinalis (0. F. Muell.) Rabh. ?] SPECIES LIST Fragilaria crotonensis Kitton Gomphonema sp. [parvulum var. micropus Chlorophyta (Kuetz.) Cl. ?] Hannaea arcus Patr. Cosmarium bioculatum var. depressum Melosira distans var. alpigena Grun. (Schaar.) Schm. impressulum Elfv. is/and/ca subsp. he/vet/ca 0. Muell. *Dictyosphaerium pulchellum Wood Navicula rhynocephala Kuetz. Eudorina elegans Ehr. Pinnularia abaujensis var. linearis (Hust.) Patr. Mougeotia sp. major (Kuetz.) Rabh. Oocystis borgei Snow mesolepta (Ehr.) W. Sm. *Sphaerocystis schroeteri Chod. Stauroneis phoenocenteron F. gracilis (Ehr.) *Staurastrum longiradiatum W. and W. Hust. Tetraspora lacustris Lemm. Sur/re//a sp. (biseriata Breb. ?) Volvocale spores *Synedra amphicephala Kuetz. Zoochlorellae (in Heliozoan) ? *delicatissima W. Sm. *radians Kuetz. Euglenophyta *ulna var. danica (Kuetz.) VH *Tabellaria flocculosa (Roth) Kuetz. Co/ac/urn vesiculosum Ehr. Euglena sp. Pyrrophyta Trachelomonas rugulosa Stein Ceratium hirundinella (0. F. Muell.) Duj. Chrysophyta Glenodinium gymnodinium Penard Per/din/urn inconspicuum Lemm. *Dinobryon cylindricum Imhof. willei Huit.-Kaas. *Mallonomas elongata Rever. *pseudocoronata Presc. Cyanophyta

Bacillariophyta Anabaena flos-aquae (Lyngb.) Breb. Cyanellae (in Heliozoan) ? *Asterionella formosa Hass. *Oscillatoria amphibia C.A. Ag. Cyclotella bodanica Eulenst. *tenuis C.A. Ag. comta (Ehr.) Kuetz. meneghiniana Kuetz. Total: 50 species Cymbella affinis Kuetz. cusp/data Kuetz. ventricosa Kuetz. * Commonly occurring limnetic phytoplankters listed in Diatoma hiemale var. mesodon (Ehr.) Grun. table 2.

15 Table 3. — Twin Lakes phytoplankton Table 3. — Twin Lakes phytoplankton — continued

Upper Lower Upper Lower 6-24-74 6-25-75 6-24-74 6-25-75 Chlorophyta Fragilaria crotonensis Gomphonema sp. (parvulum Cosmarium biocula turn var. var. micropus ?) depressum P1 Hannaea arcus Cosmarium impressulum Melosira distans var. Dictyosphaerium pulchellum alpigena Eudorina elegans Melosira island/ca subsp. Mougeotia sp. helvetica Oocystis borgei Navicula rhynocephala Sphaerocystis schroeteri C2 Pinnularia abaujensis var. Staurastrum longiradiatum linearis Tetraspora lacustris Pinnularia major Volvocale spores Pinnularia mesolepta Zoochlorellae (in Heliozoan) ? Stauroneis phoenocenteron F. gracilis Euglenophyta Surirella sp. (biseriata ?) Synedra amphicephala Colacium vesiculosum Synedra delicatissima Euglena sp. (balled) Synedra radians Trachelomonas rugulosa Synedra ulna var. danica Tabellaria flocculosa Chrysophyta Pyrrophyta Dinobryon cylindricum A' Mallonomas elongata Ceratium hirundinella Mallonomas pseudocoronata Glenodinium gymnodinium Per/din/urn inconspicuum Bacillariophyta Peridinium willei Cyanophyta Aster/one/la formosa A Cyclotella bodanica Cyclotella comta Anabaena flos-aquae Cyclotella meneghiniana Cyanellae (in Heliozoan) ? Cymbella affinis Oscillatoria amphibia Cymbella cusp/data Oscillatoria tenuis Cymbella ventricosa Diatoma hiemale var. ' P = present. mesodon 2 C = common. Eunotia sp. (pectinalis?) 3 A = abundant.

1 6 TWIN LAKES, COLO., BUREAU OF RECLAMATION* — LIMNOLOGY REPORTS (REC—ERC NO.)

76-12 Studies of the Benthic Environment of Twin Lakes, Colorado, LaBounty, James F., ed. 76-14 Ecology of Mysis Relicta in Twin Lakes, Colorado, Gregg, Ronald E., (Colorado Cooperative Fishery Unit, CSU, Ft. Collins) 76-15 Dive Studies at Twin Lakes, Colorado, 1974-75, LaBounty, J. F., R. A. Crysdale, and D. W. Eller

77-4 The Lake Trout of Twin Lakes, Colorado, Griest, John R. (Colorado Cooperative Fishery Research Unit, CSU, Ft. Collins) 77-13 Historical, Physical, and Chemical Limnology of Twin Lakes, Colorado, Sartoris, J. J., J. F. LaBounty, and H. D. Newkirk

79-17 Movements of Lake Trout in Twin Lakes, Colorado, in Relation to the Mt. Elbert Pumped- Storage Powerplant, Walch, Leonard A. (Colorado Cooperative Fishery Research Unit, CSU, Ft. Collins)

80-2 Ecology of Catostomids in Twin Lakes, Colorado, in Relation to a Pumped-Storage Powerplant, Krieger, Douglas A. (Colorado Cooperative Fishery Research Unit, CSU, Ft. Collins) 80-5 Results of Fisheries Investigations at Twin Lakes, Colorado 1973-1976, Finnell, L. M., (Colorado Div. of Wildlife) 80-7 Studies of the Effects of Operating the Mt. Elbert Pumped-Storage Powerplant on Twin Lakes, Colorado: 1979 Report of Findings, LaBounty, James F., James J. Sartoris, Sharon G. Campbell, John R. Boehmke, and Richard A. Roline

81-4 Hydroacoustic Surveys of Fish Abundance and Distribution in Twin Lakes, Colorado, Thorne, Richard E., G. L. Thomas, (Fisheries Research Institute, College of Fisheries, U. of Washington)

82-3 The Relative Abundance of Mysis Relicta in Twin Lakes, Colorado, Using a Benthic Trawl, Nesler, T. P. 82-4 Twin Lakes Studies: A Characterization of the Twin Lakes Fishery via Creel Census with an Evaluation of Potential Effects of Pumped-Storage Power Generation, Nesler, T. P. 82-6 Limnology of Mt. Elbert Forebay, 1978-79, Boehmke, J. R., J. F. LaBounty, J. J. Sartoris, and R. A. Roline 82-7 Studies of the Effects of Operating the Mt. Elbert Pumped-Storage Powerplant on Twin Lakes, Colorado, 1980 Report of Findings, LaBounty, J. F. and J. J. Sartoris 82-21 Common Plankton of Twin Lakes, Colorado, Lieberman, Davine M.

OTHER USBR FRYINGPAN-ARKANSAS PROJECT REPORTS (REC-ERC NO.)

75-5 Assessment of Heavy Metals Pollution in the Upper Arkansas River of Colorado, LaBounty, J. F., J. J. Sartoris, L. D. Klein, E. F. Monk, and M. A. Salman 81-15 Heavy Metals Pollution of the Upper Arkansas River and the Effects on the Distribution of the Aquatic Macrofauna, Roline, R. A. and J. R. Boehmke 82-5 Studies of the Limnology, Fish Populations, and Fishery of Turquoise Lake, Colorado —1979-80, Nesler, T. P.

* From Nov. 1979 to May 1981, Bureau of Reclamation was known as the Water and Power Resources Service.

17 GPO 839-079 Mission of the Bureau of Reclamation

The Bureau of Reclamation of the U.S. Department of the Interior is responsible for the development and conservation of the Nation's water resources in the Western United States.

The Bureau's original purpose "to provide for the reclamation of arid and semiarid lands in the West" today covers a wide range of interre- lated functions. These include providing municipal and industrial water .supplies; hydroelectric power generation; irrigation water for agri- culture; water quality improvement; flood control; river navigation; river regulation and control; fish and wildlife enhancement; outdoor recreation; and research on water-related design, construction, mate- rials, atmospheric management, and wind and solar power.

Bureau programs most frequently are the result of close cooperation with the U.S. Congress, other Federal agencies, States, local govern- ments, academic institutions, water-user organizations, and other concerned groups.

A free pamphlet is available from the Bureau entitled, "Publications for Sale". It describes some of the technical publications currently available, their cost, and how to order them. The pamphlet can be obtained upon request from the Bureau of Reclamation, Attn D-922, P 0 Box 25007, Denver Federal Center, Denver CO 80225-0007.