Journal of the Arkansas Academy of Science

Volume 37 Article 20

1983 Phytoplankton Community Structure in Dardanelle Reservoir, Arkansas, 1975-1982 John D. Rickett University of Arkansas at Little Rock

Robert L. Watson University of Arkansas at Little Rock

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Recommended Citation Rickett, John D. and Watson, Robert L. (1983) "Phytoplankton Community Structure in Dardanelle Reservoir, Arkansas, 1975-1982," Journal of the Arkansas Academy of Science: Vol. 37 , Article 20. Available at: http://scholarworks.uark.edu/jaas/vol37/iss1/20

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PHYTOPLANKTON COMMUNITY STRUCTURE IN DARDANELLE RESERVOIR, ARKANSAS, 1975-1982

JOHN D. RICKETT and ROBERT L.WATSON Biology Department University of Arkansas at Little Rock Little Rock, Arkansas 72204

ABSTRACT Phytoplankton data were collected with standard equipment and procedures over an eight-year period (1975-1 982) inDardanelle Reservoir, Arkansas. Community abundance and diversity at the genus level are described. Sixty-five genera representing 35 families and five divisions were identified. Total phytoplankton abundance and diversity were quite uniform among the stations but fluctuated considerably withtime. These fluctuations didnot correspond clearly withseason. Dominant taxa were seasonal, though, with diatoms being usually dominant in January, Apriland October, and blue-greens dominant in July. The phytoplankton community structure has not been significantly altered bythe operation ofANO UnitI.

INTRODUCTION Information about phytoplankton community structure in Arkansas reservoirs is quite scarce. Some ofthe earlier papers (Meyer, 1969; Meyer et a!., 1970) dealt only with checklists, whereas others studied algae inrelation to certain water quality parameters (Meyer, 1971; Rice and Meyer, 1977). Still other studies emphasized phytoplankton populations related to certain anthropogenic inputs, e.g., thermal discharge. Sinclair and Watson (1978) conducted such a survey inDardanelle Reservoir for fiveyears immediately prior to the operation ofArkansas Power and LightCompany's Arkansas' Nuclear One (ANO)Unit I.Numerous papers have appeared concerning thermal disturbance in specific loca- tions inother states (Gibbons and Sharitz, 1974; Esch and McFarlane, 1976). There is a definite lack in Arkansas of work describing phytoplankton community structure and dynamics and the impacts of thermal effluents. This report is a superficial analysis ofdata gathered inDardanelle Reservoir over an eight-year post-operational period of ANO Unit I. The main points to be addressed in this paper are (1) seasonally orperiodicity ofcommunity diversity and which taxa were dominant and when, (2) changes in abundance and diversity related to Figure 1. Plankton sampling stations on Dardanelle Reservoir, season and location with respect to thermal discharge, and (3)evidence Arkansas, 1975-1982. oflong-term trends or shifts in community structure. RESULTS ANDDISCUSSION METHODS AND MATERIALS Sixty-five genera representing 35 families in five divisions were Phytoplankton samples were collected inJanuary, April,July and identified (Table 1). Forty-six percent ofthe genera were inChlorophyta, October ofthe years 1975-1982 and strained through a standard No. 31 were in Chrysophyta, 17 were in Cyanophyta, and Euglenophyta 20 Wisconsin-style plankton net. The water column at each station and Pyrrhophyta represented by percent genera. bottom, and were three each ofthe date was sampled by taking 2 1 of water each from near the Meyer (1969) reported 82 genera as occurring in Arkansas; of which surface, 29 mid-depth and 0.6 m, and 4 1 from the constituting a 10 1 were present in this study. Meyer et ai, (1970) reported an additional sample. With rare exceptions, 10 stations were sampled quarterly (Figure 34 Arkansas genera, eight of which are reported in this study. Nelson 1) and the samples preserved in Meyer's Fixative (0.76% I2,0.38% KI, Harp (1972) reported genera were obtained 0, and four additional which 3.8% glacial acetic acid, 19% concentrated formalin and 76% dH2 in our study. This study presents 24 genera not reported by any ofthe by weight). three foregoing papers. In the lab the samples were diluted to 10 ml(ifneeded), and a 1 ml Table 2is a summary by season (quarter) ofindividuals, number of aliquot was removed and placed in a Sedgwick-Rafter counting cell. taxa, individuals per taxon and diversity values listing stations close Quantitative evaluation was determined by counting randomly spaced to and distant from the point ofthermal discharge. Close stations (Nos. strips across the counting cell to cover 38.9 percent ofthe area. Then 1,2,3,5,10) were those generally influenced by thermal loading, whereas . a total quantitative cross-check was made by counting 10 randomly distant stations (Nos. 11,14,15,16,21) were those not apparently chosen fields. Colonial forms were counted as single cells, and organisms influencd (Rickett, 1981). Acursory examination of Table 2reveals con- were identified to genus where possible and reported as number per liter. siderable fluctuation from quarter to quarter and from year to year. Statistical procedures included calculation of the number of taxa, On the average, July samples contained the largest populations, number ofindividuals, mean number ofindividuals per taxon and com- numerically, the greatest number of taxa and the largest number per munitydiversity at the generic level. Diversity was calculated using the taxon, but the greatest community diversity indices were observed in October. Phytoplankton was very dense inJuly 1978, exhibited a serious Shannon Index, d = -E (-S-)ln(-R-), where n, is the number of decline in January 1981 and arapid recovery between Apriland July 1981. Thedecline was probably a delayed response to the very hot and organisms ineach taxon inturn, and Nis the total number oforganisms dry summer of 1980. Total phytoplankton peaked six times in July, per liter. Values are positive; the larger ones indicating greater com- four times inJanuary and once inApril.The peaks were spread bysix munity diversity. to 12 months, so there was not a precise coincidence with season.

Published by Arkansas Academy of Science, 1983 70 Academy Proceedings, XXXVII, 70 Arkansas of Science Vol. 1983 Journal of the Arkansas Academy of Science, Vol. 37 [1983], Art. 20

John D. Rickett and Robert L.Watson

Table 1. of phytoplankton in Dardanelle Reservoir, Table 2. Summary by season (quarter) of phytoplankton community Arkansas, 1975-82. structure, Dardanelle Reservoir, Arkansas, 1975-82. n Family Desmidiaceae nivisi° JANUARY Number of Number Number Diversity Family Chlamydomonadaceae 28. Closterium Year Stations Organisms of taxa per taxon Value 1. Chlamvdomonas 29. Cosmarium Family Volvocaceae 30- Staurastrum ,Q7, Close 1309 12.7 104 1.796 2. Eudorina Distant 1214 11.5 104 I.638 3. Gonium Division Chrysophyta ,„,.'° Close 5271 16.4 324 1-839 4. Pandorina Family Tribonemataceae v Distant 5942 17.8 337 I.916 *5• Platydorina 31 Tribonema . lq77 Close 5061 16.4 309 1.997 6. Volvox Family Chrysococcaceae *'' Distant 20.0 353 1.895 Family Chrysococcus 7064 32. 16.2 •7- Gloeococcus Family Dinobryaceae lq7By'° Close 3338 209 1-459 Family Chlorococcaceae 33. Dinobryon Distant 2651 14.2 189 1.462 •8. Schroederia Family Synuraceae 1Q70**" Close 1336 14.8 90 2.086 Family Palmellaoeae 34. Synura Distant 1206 12.3 98 1-956 9. Sphaerocystis Family Coscinodisoaceae Close 12.4 Family Oocystaceae 1980y 4635 376 1.710 35. Cvclotella Distant 12.8 350 10. Ankistrodesmus Melosira 4452 1.842 36. .„„. 82 2.6 11. Chlorella *J? • Stephanodiscus y Close 29 O.7560.756 ?12. Chodatella Family Fragillariaceae Distant 92 2.8 32 0.582 Kirchneriella Asterionella 13- 38. 1982 Close 4385 10.2 430 1.579 Family Micractiniaceae Fragillaria ____ Distant 2?§? 0.;2 14 Micractinium 39. i ?2? .Aliit. . •40. Meridion Close 3177 12 "7 1>65 Synedra mMeanan 2^* Family Dictyosphaeriaceae 41 Distant 12.7 223 1-594? 15- Dictyosphaerium 42.. Tabellaria 3238 •16. Dimorphococcus Family Naviculaceae APRIL Family Scenedesmaceae Gyrosiema , Close *43. 107y° 5012 17.0 300 1.869 17- Actinastrum »44. Navicula Distant 5467 16.6 338 1.755 18 Coelastrum Neidium . »45. ,,« Close 2464 18.8 130 2.183 19. Crucigenia *46. Stauroneis L)"° Distant 2418 16.4 2.060 20. Scenedesmus Family Gomphonemaceae 147 164 Family Hydrodiotyaoeae *4?. Gomphonema lq77y" Close 2851 17.0 2.128 21. Pediastrum Family Cymbellaceae Distant 3803 16.0 247 2.045 Family Ulotrichaceae Cymbella »48. lq7fiy'° Close 5617 16.8 335 1.810 *22. Ulothrix Family Nitzschiaoeae Distant 5

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Phytoplankton Community Structure in Dardanelle Reservoir, Arkansas, 1975-1982

The major community growthoccurred in July withaminor growth Unit Iduring periods of operation, the average AT's were 8.20, 744 period in January. Olsen and (1976) 1980, 1982, Sommerfield obtained similar and 5.99°C for 1981 and respectively. Gurtz and Weiss periods ofabundance and depression in Canyon Lake, Arizona. They (1974) studied experimental AT's of 5.6, 11.1 and 16.7 °C also and noted that the early spring peak was composed primarily ofcen- observed continually increasing inhibition of phytoplankton produc- tricdiatoms, whereas the mid- to late-summer peak was dominated by tivity.Tilly(1974) obtained an average 20% increase in autotrophic filamentous Cyanophyceae. respiration in AT's ranging up to 3.3 °C whilethere was no significant Between July and October there was a decline inboth numbers of increase inphotosynthesis. Patrick (1974) summarized bypointing out organisms and taxa, but the former apparently experienced a dispropor- that small AT's stimulate while large AT's inhibit and cause changes tionate decline whichcaused higher diversity values. This also happened in the composition ofthe community to favorblue-green algae somewhat between January and April.Both normal seasonal decline Thermal shock usually had detrimental effects. Most ofthese studies and zooplankton cropping may have been the cause. have been conducted in eastern or northeastern United States, so these Table 3 shows dominance timing and frequency ofnine major genera conclusions may not necessarily applyhere. More geographic variation during the study period considering each station each quarter. Cyclolella has been observed than was expected. was the dominant (represented by the greatest number ofcells) 86 times, far more than any other taxon, and its favored time was October (47.7% oftotal for Cyclotella). Melosira and Oscillatoria were dominant with SUMMARY about the same—frequency (54 and 53 times, respectively) but favored different times January for Melosira (38.9%) and July for Oscillatoria Itis always difficult to separate variables, especially when so many (77.4%). Tribonema was dominant 34 times (58.8% of the time in are present. Inaddition to daily temperature variations, wind velocity January), while Asterionella and Navicula were dominant 13 times each. and direction, solar radiation and physico-chemical characteristics Asterionella favored April(100%), whereas Navicula favored October further confuse the understanding. Add to this the fact that Dardanelle (84.6%). Reservoir has two distinct areas, and water from one (IllinoisBayou) ispumped through the plant into the other (Arkansas River mainstream), thus mixing parameters. Include the somewhat sporadic operation of Table 3. Dominance timingand frequency ofmajor phytoplankton taxa ANOUnit I,and the challenge of understanding becomes inDardanelle Reservoir, Arkansas, 1975-1982. steeper. These data suggest that phytoplankton diversity and abundance were Number of times dominant per quarter 1 fairlyuniform at the various sampling stations, there was considerable Dominant taxon JAN APR JUL OCT Total fluctuation inabundance and numbers of taxa which did not conform Cyclotella 11 2k 10 hi 86 closely to the seasons, dominant taxa were quite seasonal in their oc- (Chrysophyta ) currence, the diatoms being usually dominant in January, Apriland Melosira 21 13 16 k 51* October while the blue-green algae were dominant inJuly. Blue-green (Chrysophyta ) algae is apparently better adapted to warmer water since they may take Oscillatoria 1 6 **1 5 53 over as dominants inarea ofthermal effluent. Power plant operation ( Cyanophyta ) has not noticeably affected overall phytoplankton abundance and the Tribonema 20 12 2 0 3^ number of taxa, but community diversity was slightlygreater at the (Chrysophyta ) close stations but not statistically significant. Water temperature changes Asterionella 0 13 o 0 13 through the plantmay be considered near the lower end ofthe expected (Chrysophyta) range compared to similar results elsewhere. Navicula 1 1 o 11 13 (Chrysophyta ) Ankistrode smus 3 1 0 7 11 ACKNOWLEDGEMENTS (Chlorophyta) Anabaena 0 1 l 9 11 The authors wish to thank the late Clarence B. Sinclair ( Cyanophyta ) and William R. Bowen for analyzing the phytoplankton Chlamydomonas 0030 3 samples, and numerous staff and students for field (Chlorophyta) assistance. Financial support was provided byArkansas Total 57 71 73 77 Power and Light Company.

InJanuary Melosira, Tribonema and Cyclotella were dominant 36.8, 35.1 and 19.3 %ofthe time, respectively. InAprilCyclotella,Melosira, LITERATURE CITED Asterionella and Tribonema were dominant 33.8, 18.3, 18.3 and 16.9 %, respectively. InJuly Oscillatoria, Melosira and Cyclotella were domi- ESCH, G. W.,and R.W. MCFARLANE. 1976. Thermal Ecology, II- nant 56.2, 21 .9 and 13.7 %, respectively, whereas in October Cyclotella, ERDA Symposium Series 40. 404 pp. Navicula and Anabaena were dominant 53.2, 14.3 and 11.7%, respec- tively. In January, April and October, Chrysophyta were strongly GIBBONS, J. W., and R. R. SHARITZ. 1974. Thermal Ecology, dominant, whereas Cyanophyta dominated in July. Evidence of the I.AEC Symposium Series. 670 pp. 1 dominance shift back to Chrysophyta was seen inOctober. Data col- lected by Sinclair and Watson (1978) during pre-operational years GURTZ, M. E.,and C. M.WEISS. 1974. Effect ofthermal stress on (1970-74) showed the same dominance trends for the diatoms phytoplankton productivity incondenser cooling water. In:Thermal (Chrysophyta) versus the blue-greens (Cyanophyta). Chlorophyta was Ecology, I,ed. by J. W. Gibbons and R. R. Sharitz, AEC Sym- represented less strongly in spite ofhaving the greatest number ofgenera. posium Series, pp. 490-507. Aconsiderable number of researchers have attempted to assess and quantify the impacts of thermal discharges, mostly from generating MEYER, R. L. 1969. The freshwater algae ofArkansas. Proc. Ark. stations into natural waters. Miller et al. (1976) worked with actual AT's Acad. Sci. 23:145-155. between 8.5 and 15°C and concluded that smaller AT's that did not push the ambient temperature above 25 CC were stimulatory, but 34 CC MEYER, R. L. 1971. A study of phytoplankton dynamics inLake was definitely inhibitory.One oftheir major problems was separating Fayetteville as ameans ofassessing water quality. Ark.Water Res. the effects ofthermal discharge and normal ambient variation. At ANO Res. Enter, Publ. No. 10. 59 pp.

Published by72 Arkansas Academy of Science,Arkansas 1983Academy of Science Proceedings, Vol. XXXVII,1983 72 Journal of the Arkansas Academy of Science, Vol. 37 [1983], Art. 20

John D. Rickett and Robert L. Watson

MEYER, R. L., J. H. WHEELER, and J. R. BREWER. 1970. The RICE, R. G., and R. L.MEYER. 1977. Algal assemblage distribution freshwater algae of Arkansas, II.New Additions. Proc. Ark.Acad. as related to seasonal fluctuations ofselected metal concentrations. Sci. 24:32-35. Proc. Ark.Acad. Sci. 31:90-91.

MILLER,M.C, G.R. HATER, T.W. FEDERLE, and J. D.REED. RICKETT,J. D. 1981. Temperature and dissolved oxygen profiles in 1976. Effects ofpower-plant operation on the biota ofa thermal Dardanelle Reservoir, 1971-1980. Unpubl.paper presented at the discharge channel. In:Thermal Ecology, II,ed. by G. W. Esch Ark. Acad. Sci. meeting, Little Rock, AR, 17, 18 Apr 1981. and R. W.McFarlane, ERDA Symposium Series 40,pp. 251-258. SINCLAIR,C. B., and R. L.WATSON. 1978. A primary ecological NELSON, J. H., and G.L.HARP. 1972. Qualitative and quantitative survey of Dardanelle Reservoir prior to nuclear facility effluent variation ofnet plankton of Craighead Lake. Southw. Naturalist discharge. Ark. Water Res. Res. Center, Publ. No. 60. 17(3):239-248. TILLY,L.J. 1974. Respiration and net productivity ofthe plankton 0LSEN, R. D., and M.R. SOMMERFIELD. 1976. Thermal ecology community in a reactor cooling reservoir. In:Thermal Ecology, of phytoplankton in a desert reservoir. In:Thermal Ecology, II, I,ed. by J. W. Gibbons and R. R. sharitz, AEC Symposium Series, ed. byG. W. Esch and R. W. McFarlane, ERDA Symposium Series pp. 462-474. 40, pp. 195-201.

PATRICK, R. 1974. Effects of abnormal temperatures on algal communities. In:Thermal Ecology, I,ed. by J. W. Gibbons and R. R. Shartiz, AEC Symposium Series, pp. 335-349.

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