AGRICULTURAL EXPERIMENT R. Dennis Rouse, Director STATION / AUBURN UNIVERSITY Auburn, Alabama Phytoplankton and Water Quality in a Fertilized Fish Pond CIRCULAR NOVEMBER 224 1975 4 CONTENTS Page METHODS AND MATERIALS ---------------3 The Study Area---- --- ---- --- ---- --- ---- - -- - - 3 Phytoplankton and Chemical Analysis-4 Physical Conditions --- -- --- -- --RESULTS AND DIScUSSION-------------- ----- -- ------ -- 4 -5 Phytoplankton - - - - - - --- - - -10 - - - - - - 5--- W ater Temperature------------------ D issolved O xygen ---Light- - - -13-- ---- ---- --- ---- - ---- - --- -13 - ------- ---------------------------14 -14 16 Alkalinity and pH ---- --- ---- Nitrogen and Phosphorus ---------LITERATURE CITED ------------------------------------ FIRST PRINTING 2M, NOVEMBER 1975 SECOND PRINTING 2M, OCTOBER 1976 Auhurn University is an equal opportunity employer [2] Phytoplankton and Water Quality inA Fertilized Fish Pond' 2 R. W. PARKS, ELLEN SCARSBROOK, and C. E. BOYD ARE FREQUENTLY added to fish ponds to increase the abundance of microscopic plants (phytoplankton) and animals (zooplankton) and thereby stimulate fish production (17, 22). High concentrations of nutrients often favor the development of dense blooms of blue-green algae (5). Under certain conditions, heavy blooms of blue-green algae are responsible for a number of problems in ponds, including odors (21), bad tastes in fish (15), presence of toxic substances (21), and shallow chemical and thermal stratification of the water (4). Some populations of algae, particularly species of Microcystis and Anabaena, may die suddenly (8,23). Decomposition may cause oxygen depletion and fish kills (8,23). The present investigation was initiated to monitor changes in phytoplankton and water quality in a fertilized fish pond. Emphasis was given to determining relationships between the abundance and periodicity of phytoplankton and changes in water quality. FERTILIZERS METHODS AND MATERIALS The Study Area Pond S-3 on the Fisheries Research Unit of the Auburn University Agricultural Experiment Station has an area of 9.75 acres and an average depth of about 5 feet. It is filled by overflow from other ponds (S-2, S-24, and S-25) and by runoff. The pond 1 This research was supported by the Office of Water Research and Technology the Department of the Interior through the Water Resources Research Institute of Auburn University under provisions of the Water Research Act of 1964. Associate, and Associate Professor, respectively, 2 Graduate Assistant, Research Department of Fisheries and Allied Aquacultures. [38 was drained in November, 1967, and stocked on February 5, 1968, with 9,780 fingerling bluegill sunfish (Lepomis macrochirus Rafinesque), 4,875 fingerling redear sunfish (Lepomis microlophus (Gunther)), 19,500 fathead minnows (Pimephales promelas Rafinesque), and 20 subadult largemouth bass (Micropterus salmoides (Lacepede)). Threadfin shad, Signalosa petenensis (Gunther) were also present. Ten applications of 17.4 pounds per acre of triple superphosphate were made during each growing season. Fishing was allowed in the pond on a limited basis. Phytoplankton and Chemical Analyses A sampling station was selected near the dam of S-3 where the depth of water was 10 feet. Water for phytoplankton enumeration was collected at 18-inch intervals with a weighted bottle sampler (16). Samples were taken at approximately 8 a.m. at 2 or 3-day intervals while phytoplankton growth was slow, and daily when phytoplankton was growing rapidly. Phytoplankton was concentrated by filtration through sand and counted in a counting chamber under a microscope fitted with an ocular micrometer (2). Dissolved oxygen determinations were made at the various depths at the sampling station with a polarographic oxygen meter. Water samples for chemical analyses were taken each time phytoplankton samples were collected. These samples were collected with a brass water column sampler which enclosed a column of water 36 inches in length by 2 inches in diameter (5). Soluble orthophosphate, nitrate, and ammonia concentrations were measured by standard colorimetric procedures described by the American Public Health Association (2). Alkalinity was measured by titration with 0.02N H 2SO4 and free carbon dioxide was titrated with 0.02N NaOH (2). A glass electrode was used to measure pH. Physical Conditions A temperature profile was taken on each sampling date with a submersible thermometer. An underwater light meter was used to measure light intensities at 18-inch intervals. A Secchi disk was used to determine the depth of visibility on each sampling date. A recording solarimeter recorded incoming solar radiation continuously from a location on the shore of the pond. Records of average daily air temperature and total daily wind run were [4] obtained from the Environmental Studies Service Center, Auburn University. The data were collected at a weather station on the Auburn University campus. RESULTS AND DISCUSSION Phytoplankton Data on the abundance of different genera of phytoplankton are presented in figures 1, 2, 3, 4, and 5. Two genera, Anabaena and Microcystis, were more important numerically and ecologically than other genera. The abundance of these two genera is reported as individuals per milliliter, figures 1 and 2. The abundance of other genera is expressed as logarithms to the base 10 of the numbers of individuals per milliliter, figures 3, 4, and 5. Algae present in the winter and early spring included the following groups; blue-green algae-Anabaena,Microcystis, Spirulina, Oscillatoria, Raphidiopsis, and Gomphosphaeria, green algaeSelenastrum, Kirchneriella, Consmarium, Arthrodesmus, Staurastrum, Sphaerocystis, Pandorina, and Oocystis, euglenophytes Trachelomonas. In late March, Anabaena began to increase in abundance and during late April and May individuals of this genus comprised 50 percent or more of the total phytoplankton. Most of the other genera declined in abundance or disappeared from the phytoplankton community with the increase in Anabaena. Filaments of Anabaena were buoyant and accumulated in the surface water, Figure 1. Buoyancy of the blue-green algae results from gas vacuoles which form in cells exposed to low light intensity (10,11). Plankton absorbs and reflects light and is a major factor affecting the penetration of light in fertilized ponds (4). Therefore, the depth of penetration of adequate light for photosynthesis is inversely related to the abundance of phytoplankton (4). Surface scums of Anabaena formed on calm days and drifted to the leeward shore. Moderate or heavy winds or rain prevented scums by mixing Anabaena in the water column. A number of partial die-offs of Anabaena occurred between late March and early June. The dates for five of the best defined dieoffs are marked on Figure 1. Data on weather conditions, which were apparently responsible for die-offs, are presented in figures 6 and 7. A similar pattern of events was associated with each die-off. Surface scums of Anabaena were present in the morning after a night of calm weather. On clear calm days, the scum per[5] sisted and the bright light apparently injured filaments in the scum. Algae in the scum turned brown by afternoon and began to disintegrate and decompose. These observations are in agreement with findings for another pond where light injury to Anabaena in a surface scum apparently triggered a massive phytoplankton die-off with subsequent depletion of dissolved oxygen (8). Fortunately, only a portion of the Anabaena in S-3 died on 40 Surface 3530 25Anoboeno circinolis i-1 Other Phytoplonkton 20 15 10 5 0 O- 10 15 5 Average af all depths 0 February March April May June FIG. 1. Abundance of Anabaena in relation to the total abundance of phytoplankton in S-S. Arrows indicate partial die-offs of Anabaena. [6] each occasion, Figure 1, and water quality was not seriously impaired. Observations made during the present study do not reveal the mechanism by which Anabaena attained dominance in the toplankton community. However, the two following possibilities are most appealing to the authors. First, the buoyant filaments of Anabaena accumulated near the surface and shaded phytoplankton that was unable to rise towards the where light intensities were higher. Second, laboratory studies have revealed that Anabaena excretes substances into the water which are toxic to other algae (6,19). Admittedly, many other factors phy- surface 30 20 I0L 0 20I0 0 20t 20 Surface d Microcysfis aeruginosa 0 Other Phytoplankton 3 feet 6 'feet 10 U)100- 20100- Average May June July August FIG. 2. Abundance of Microcystis in relation to the total abundance of phytoplankton in S-3. [7] including temperature, pH, and nutrient concentrations may also have contributed to the increase in Anabaera. The abundance of Microcystis increased rapidly in June after Anabaena declined in number. The abundance of Microcystis scums also was greater in surface waters, Figure 2, and often. No die-offs or scums of of Microcystis were observed was not Microcystis occurred. This suggests that bright was to Anabaena. A number of as harmful to Microcystis as it genera, Microcystis, Selenastrum, Arthrodesmus, Spirulina, Meiismopedia, Oscillatoria, Raphidiopsis, Gomphosphaeria, Sphaerocystis, Trachelomonas, Jandorina, Qocystis, Kirchneriella, Cosmariun, and Staurastrum were present in samples taken on one surface light 2 Se/enstrum 2L~ 2 Kirchnerie//a 4 2 On JI ~Cisritim 2 Atrodesmus - F M A M J J A FIG. 3. Seasonal succession of plamktonic algae in S-3 from February 1974 to September 1974. Data represent the average abundance of phytoplankton in the water column. [8 ] 2 Sp/aerocysfis 2 Troche/omonas E o 2 a 2 Pander/no o 2 Oocystis F M A M J J A S FIG. 4. Seasonal succession of planktonic algae in S-3 from February 1974 to September 1974. Data represent the average abundance of phytoplankton in the water column. or more dates between June 1 and August 15. Individuals of Microcystis greatly outnumbered individuals of any other genus during this time. Reasons for the dominance of Microcystis cannot be explained from data at hand. Microcystis is known to excrete substances toxic to other algae (6,19) and individuals of this genus have a competitive advantage for light and carbon dioxide since they accumulate near the surface. The abundance of Microcystis declined to a August 15. Three .other blue-green algae, Spirulina, Merismopedia, and Oscillatoria were abundant after the decline of Microcystis. The decline of Microcystis may have been related to any one or more of the factors mentioned above. Changes in the abundance of individual species of phytoplankton such as those observed in S-3 are common in natural waters (7,9,20,22,25). These changes have been attributed to a number of factors including, pH, temperature, nutrient concentrations, [9] low level after 2r Spiruhrno rrn 2 Merismopedia 2 Oscil/aloria 'F °F 0 2 2 Rophidiopsis 2,-. 2 Gomphosphaerio F M A M J J A S FIG. 5. Seasonal succession of planktonic algae in S-3 from February 1974 to September 1974. Data represent the average abundance of phytoplankton in the water column. light, weather, diseases, parasites, grazing by fish and zooplankton, and toxins (9). Unfortunately, data collected in most studies have not been adequate to isolate with certainty the factor or factors affecting these changes in algal species. Water Temperature Water in S-3 was nearly isothermal in the early morning from February until early March, Figure 8. Water temperatures, then increased faster in the upper 3 feet of. water than in the lower ° waters, and on March 10 the surface water was 22 Fahrenheit warmer than water at a depth of 9 feet. Heavy winds during [10] 8 7 E 6 5a) 4 3 CD a) 2 a I 0 80 CZ °--70 S60 'a 50 H40- < 30 February March April May June July August FIG. 6. Mean air temperatures and total wind runs as recorded by the Environmental Studies Service Center, Auburn University, Auburn, Alabama. Arrows indicate times when partial die-offs of Anabaena occurred. FIG. 7. Incident solar radiation and underwater light penetration for pond S-3. [ 11 ] mid March mixed the waters, and by March 25 waters were again almost isothermal. There was a general subsidence of winds as spring progressed and water temperatures stratified again. ° Surface waters were usually 15 to 20 ° Fahrenheit warmer than bottom waters from mid April until the end of the study in early September. Temperatures at the Surface and at a depth of 3 feet were usually similar, but below 3 feet temperatures dropped sharply. There was little mixing of the upper 3 feet of water with deeper water. The average temperature of the water column increased as the study progressed; 50° Fahrenheit on February 26, 74 ° Fahrenheit on May 25, and 81 ° Fahrenheit on August 27. The plankton organisms absorbed heat and increased the heat content of near surface waters. Wind mixing of the surface water aided in distributing heat within the upper 3 or 4 feet. Warming of the water column has a direct effect on phytoplankton succession. Hammer (12) found that blooms of blue-green algae appeared in Canadian lakes when water temperatures increased above 570 Fahrenheit. In S-3, the appearance of dense blooms of Anabaena occurred when surface waters reached 59 ° 80U- ---- SSurface 3 feet feet 9 feet .6 70 E 601 0 50 12 . a. . -I . I . . II. I . . . I . II I Q 10 8 S6 - . i \ '1 .: ! ... i " v V . I\;.. \ 1 \\/ 1 1\ /\ 0 4 o ._ 11/1' 0 1 1 1I I i 1 I i i1 I iI 11 1I JI I I I I I tI 1 1! I i i 1 i I 1 I February March April May June July August FIG. 8. Dissolved oxygen and temperature data for selected depths in S-3. [12] IO 2:8 a 6 60.voE 4 S o Cl21 0 . o0 . . . . .. 16 12 8 _> 4 UJ 0 - Bicarbonate alkalinity Hydroxide alkalinity _ []Carbonate alkalinity o February March April May June July August FIG. 9. Values for alkalinity, pH, and free carbon dioxide in the upper 3 feet of water in S-3. Fahrenheit and Microcystis blooms appeared when surface waters reached 680 Fahrenheit. Dissolved Oxygen Concentrations of dissolved oxygen were normally highest at the surface and lowest near the bottom of S-2 during February and March, Figure 8. In early April, dissolved oxygen concentrations near the bottom declined to 0 ppm, and by the end of April dissolved oxygen concentrations reached 0 ppm at 6 feet. Concentrations of dissolved oxygen at the surface at a depth of 3 feet were usually above 6 ppm and at no time did they drop below 3 ppm. Surface waters often were supersaturated with dissolved oxygen. The frequent sharp declines in dissolved oxygen concentrations of the upper waters were caused by periods of cloudy weather or by partial die-offs of the phytoplankton. Beasley (4) reported that only the upper 2 to 4 feet of water in fertilized fish ponds contained enough dissolved oxygen during the summer for fish survival. Light Variations in total solar irradiance are illustrated in Figure 7. The variations from day to day followed no statistically discern[13 1 able pattern because cloud cover strongly influenced the amount of irradiance striking the surface of the earth. For example, on two successive days solar radiation often varied by a factor of 2 or more, Figure 7. Photosynthesis of plankton is usually insignificant at levels where the intensity of the light is less than 1 percent of that at the surface (25). In S-3, the depth at which the average light intensity was less than 1 percent of incident radiation varied from 2.5 to 6 feet, Figure 7. The period of least light penetration, as measured by Secchi disk visibility and underwater light meter, came at the times of greatest surface abundance of Anabaena or Microcystis, indicating the influence of phytoplankton turbidity on the light penetration. Alkalinity and pH Waters of S-3 were soft (total hardness and total alkalinity below 20 ppm) and poorly buffered. Data for pH, carbon dioxide, and the various forms of alkalinity are presented in Figure 9. The changes in these parameters were associated with phytoplankton productivity and were similar to the changes reported in other fertilized ponds (3,7). When the phytoplankton community was growing well, carbon dioxide was used in large amounts in photosynthesis and the pH of the water increased, often to the point that carbonate and hydroxide alkalinity were measurable. The pH declined during periods when conditions were unfavorable for growth (cloudy weather, and after die-offs of certain species) and only bicarbonate alkalinity were present. King (14) suggested that blue-green algae are more efficient at obtaining carbon dioxide at low concentrations than are green algae. Results of this study are constant with his findings because bluegreen algae were particularly dominant during periods when the pH was continuously above 8.4. However, it is difficult to determine whether the high pH favored growth of blue-green algae or if the rapid growth of blue-green algae caused the high pH. Nitrogen and Phosphorus Concentrations of soluble inorganic phosphorus were normally below 0.01 ppm, Figure 10. Sharp increases of concentrations of soluble inorganic phosphorus to 0.09 ppm on March 10, 0.045 ppm on March 21, and 0.075 ppm on April 5, resulted from applications of triple superphosphate. However, phosphorus is removed from the water quickly by absorption by phytoplankton and adsorption by bottom muds (13) and increases in concentra[14] tions of soluble inorganic phosphorus following fertilization were short lived. Applications of triple superphosphate on other dates were not followed by increases in concentrations of soluble inorganic phosphorus, Figure 10. Since these applications were made during periods of intense phytoplankton growth, the assumption was made that the phytoplankton removed most of the added phosphorus from the water. Concentrations of nitrate-nitrogen and ammonia-nitrogen are given in Figure 10. There were no additions of nitrogen to S-3 during the study. Nitrate-nitrogen ranged from 0.005 ppm in early April to 0.11 in early August. The maximum concentration of ammonia-nitrogen, 0.30 ppm occurred in a sample taken in mid-March. From early June to the end of the study there was no measurable ammonia-nitrogen in S-3 at the time samples were taken. This decline in ammonia-nitrogen was probably related to the favorable influence of increased temperature on nitrification (1). Anabaena is a nitrogen fixer (18) and the fixation of nitrogen by Anabaena and by certain bacteria is a major source of nitrogen in fish ponds (24). 0.10 .075 E .050 .025 0 0.10 .075Q.050 .025 0 .30 .25 .20 Ammonia nitrogen Nitrate nitrogen Soluble inorganic phosphorus .10 .05 February March April May June July August FIG. 10. Concentrations of soluble inorganic phosphorus, ammonia and nitrate in the upper 3 feet of water in S-3. Dates of triple superphosphate additions are indicated by arrows. [15] LITERATURE CITED (1) ALEXANDER, M. 1961. Introduction to soil microbiology. John Wiley and Sons, Inc., New York. 472 pp. (2) AMERICAN PUBLIC HEALTH ASSOCIATION. 1971. Standard methods for the examination of water and waste water. 13th ed., New York. 626 pp. (3) ARCE, R. C. AND C. E. BOYD. 1975. Effects of agricultural limestone on water chemistry, phytoplankton productivity and fish production in softwater ponds. Trans. Amer. Fish. Soc. 104: (In press). (4) BEASLEY, P. G. 1963. The penetration of light and concentrations of dis- (5) (6) (7) (8) (9) (10) solved oxygen in fertilized pond waters infested with Microcystis. Proc. Ann. Conf. Southeast. Assoc. Game and Fish Comm. 17: 222-226. BOYD, C. E. 1973. Summer algal communities and primary productivity in fish ponds. Hydrobiologia 40: 357-390. BOYD, C. E. 1973. Biotic interactions between different species of algae. Weed Sci. 21: 32-37. BOYD, C. E. AND ELLEN SCARSBROOK. 1974. Effects of agricultural limestone on phytoplankton communities of fish ponds. Arch. Hydrobiol. 74: 336-349. BOYD, C. E., E. E. PRATHER, AND R. W. PARKS. 1975. Sudden mortality of a massive phytoplankton bloom. Weed Sci. 23: 61-67. FOGG, G. E. 1965. Algal cultures and phytoplankton ecology. Univ. Wisc. Press, Madison. 126 pp. FOGG, G. E. AND A. E. WALSBY. 1971. Buoyancy regulation and growth of planktonic blue-green algae. Mitt. Internat. Verein. Limnol. 19: 182-188. (11) FOGG, G. E., W. D. P. STEWART, P. FAY, AND A. E. WALSBY. 1973. The blue-green algae. Academic Press, New York. 459 pp. (12) HAMMER, U. T. 1964. The succession of "bloom" species of blue-green algae and some causal factors. Verh. Internat. Verein. Limnol, 25: 829-836. (13) HEPHER, B. 1958. On the dynamics of phosphorus added to fish ponds in Israel. Limnol. Oceanogr. 3: 84-100. (14) KING, D. L. 1970. The role of carbon in eutrophication. J. Water Pollut. Contr. Fed. 42: 2035-2051. (15) LOVELL, R. T. AND L. A. SACKEY. 1973. Adsorption by channel catfish of earthy-musty flavor compounds synthesized by cultures of blue-green algae. Trans. Amer. Fish. Soc. 102: 774-777. (16) LUND, J. W. G. AND J. F. TALLING. 1957. Botanical limnological methods with special references to the algae. Bot. Rev. 23: 489-583. (17) MORTIMER, C. H. 1954. Fertilizers in fish ponds. Her Majesty's Stationery Office, Fishery Pub. No. 5. London. 155 pp. (18) OWAGA, R. E. AND J. F. CARR. 1969. The influence of nitrogen on heterocyst production in blue-green algae. Limnol. Oceanogr. 14: 342-351. (19) PROCTOR, V. W. 1957. Studies of algal antibiosis using Haematococcus and Chlamydomonas. Limnol. Oceanogr. 2: 125-139. (20) ROUND, F. E. 1971. The growth and succession of algal populations in fresh waters. Mitt. Internat. Verein. Limnol. 19: 70-89. (21) SHILo, M. 1971. Biological agents which cause lysis of blue-green algae. Mitt. Internat. Verein. Limnol. 19: 206-213. (22) SWINGLE, H. S. 1947. Experiments on pond fertilization. Agr. Exp. Sta., Ala. Polytech. Inst., Auburn, Al. Bull. 264. 34 pp. (23) SWINGLE, H. S. 1968. Fish kills caused by phytoplankton blooms and their prevention. Proc. World Symposium on Warm-water Pond Fish Culture. FAO Fisheries Rept. 44: 407-411. (24) SWINGLE, H. S., B. C. GOOCH, AND H. R. RABANAL. 1963. Phosphate fertilization of ponds. Proc. Ann. Conf. Southeast Assoc. Game and Fish Comm. 17: 213-218. 1960. Self-shading effects in natural populations of a plank(25) TALLING, J. F. tonic diatom. Water and Leben 12: 235-242.