TAXONOMY AND ECOLOGY OF APHANIZOMENON IN FIVE MINNESOTA LAKES A THESIS SUBMITTED TO THE FACULTY OF THE GRADUATE SCHOOL OF THE UNIVERSITY OF MINNESOTA By KATHLEEN KROMER BAKER IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DECEMBER, 1976 E GRAtiff 1S7170 ABSTRACT The ecology and taxonomy of five populations of Aphanizomenon were studied. The primary objective was to determine whether discrete species were present or whether the Populations each consisted of a continuum of morphological variation. Ecological characters (eutrophy, depth of stratification, seasonal occurrence of the population, morphological characters (cell width, cell length, length to width ratio, cell shape, and presence of heterocysts and akinetes) and one Physio- logical character were examined. Seasonal variation in filament density, heterocysts and akinetes were plotted. Computer programs were used to calculate morphological data. as frequency polygons and scattergram plots. The acetylene reduction technique for nitrogen fixation was applied to lake populations and isolated colonies of Aphanizomenon. The populations differed greatly in trophic con- ditions, stratification depth, and seasonal occurrence of the populations and yet the morphological characters showed no definite hiatuses in variation of cell size or cell shape that would indicate the presence of definite species. The means of morphological variation were different for each lake yet the ranges overlapped. There was a greater difference among lakes than within individual lakes. The cultures under similar environ- mental conditions had overlapping ranges of morpho- logical variation yet discrete limits for each strain. 11 The cell characters that were the most useful were vegetative and end cell width for distinguishing between strains and population means. The populations are best described by Kamarek's epithet Aphanizomenon flos7aquae Ralfs ex Bernet et Flahault. In addition, an indication of the range of variation present is recommended. Drouet's revision of the genus Anhanizomenon is not recommended mainly because it is based on the lack of published data. 111 ACKNOWLEDGEMENTS My sincere thanks to my advisor, Professor Herbert E. Wright, Jr., for his counsel, encouragement, and financial assistance. Professor Ernst Abbe offered initial encouragement to pursue graduate studies, and Professor Alan J. Brook was instrumental in steering me toward research on the blue-green algae. My appreciation also to Professor Joseph Shapiro and Professor Robert Megard for their suggestions and financial assistance. Professor Edward Schmidt and Dr. K. Krupa provided • equipment and much assistance in gas chromatography of nitrogen-fixation. Fellow students James Pirino, John Joyce, Robert Carlson, Joel Settles, and James Butler provided much help in sampling and obtaining physical- chemical data. Professor Stepko Golubic, Boston University, supplied many helpful criticisms of my manuscript. The faculty of the Department of Botany and Plant Pathology, University of New Hampshire, and in particular Professor Arthur Mathieson, kindly provided working space during the final stages of manuscript preparation. Thank you to Dr. A. Lurvey. Mrs. Cindy McElhiney was patient and dedicated while typing the final draft. thank my husband Alan for his constant support over the duration of my graduate tenure, and for his many discussions and criticsms of my work. In many ways I thank the members of my family for their encour- agement and support. iv TABLE OF CONTENTS ABSTRACT • • . ••••••••••••••••• ACKNOWLEDGMENTS .••••••••••••••• iii 1 INTRODUCTION • . • • 61100111•••••• DESCRIPTION OF THE STUDY LAKES - Halsted Bay, Carman Bay, Spencer Pond, Squaw Lake, Elk Lake . • • • . a • • • • • • . • • METHODS I. PHYSICAL AND CHEMICAL MEASUREMENTS • • ii 2. FIELD COLLECTION AND MICROSCOPE ANALYSIS . • ••• • • • • • ii 3. NITROGEN FIXATION •••••••••• 14 4. ISOLATION AND CULTURE OF COLONIES 15 5. TAXONOMIC CHARACTERS . • • • • • . 15 6. COMPUTER PROGRAMS 600011••41•• 16 RESULTS 1. VARIATION OF FILAMENT CONCENTRATION IN THE FIVE STUDY.LAUS • . • • 6 17 a. Halsted Bay ••••••••••• 17 b. Carman Bay . • • • • . • • . • • . 19 c. Spencer Pond • • • • . • • • • • • 20 d• Squaw Lake • • • • • • • • • • • • 22 e. Elk Lake . • • • • . • a • • • • 22 2. SEASONAL VARIATION IN CELL TYPES • • • 22 3. NITROGEN FIXATION . • • • . 24 4. QUANTITATIVE MORPHOLOGICAL VARIATION . 27 a. Frequency Polygons of Quantitative Characters for Each Study Lake . 27 b. Scattergrams of Cell Length and Width for Each Study Lake and for Each Cell Type . • • • • • . 29 c. Scattergrams of Seasonal Variation of Cell Size in Halsted Bay, Carman Bay, and Spencer Pond . • 29 d. Scattergrams of Colony and Culture Variation for Halsted Bay and Carman Bay . • . • • . • . • 30 5. QUALITATIVE MORPHOLOGICAL VARIATION . 32 6. UNUSUAL MORPHOLOGICAL VARIATIONS . • . 33 DISCUSSION 1. ECOLOGY . • • • . • • • . • • . 35 2. MORPHOLOGY . • • • • . • • . • . • 51 3. TAXONOMY . • • • . • . • . • • • . • . 55 SUMMARY . • . • . • • . • • . • • . 69 LITERATURE CITED . • • • . • • . • • • • • 0 • • • • 714. vi LIST OF TABLES 1. Morphometry of the five study lakes 2. Water chemistry of the five study lakes 3. Variation in algal counts on data from Halsted Bay and Carman Bay populations 4. Variations in percent cell estimates 5. Comparison of Lugol's solution and H2SO4 for effective- ness in stopping the 'acetylene reduction reaction 6. Variation in cell dimensions (microns) for a colony, culture, lake sample (one date), and lake sample (all dates) in the Halsted Bay population 7. Six of the commonly used taxa within the genus Aphanizomenon 8. The distribution of cell shapes for each lake population 9. Comparison of range of cell dimensions (microns) for filaments with string end cells and for all filaments in a lake population 10. Range in temperature (°C) for the maximum S.R.C., optimum biomass, and presence of Aphanizomenon populations 11. Presence of cell types seasonally (sterile filaments- SF, filaments with heterocysts-H, filaments with akinetes-A, filaments with a heterocyst and akinete-AH) 12. Classification of lake populations on the basis of mean cell size for vegetative cells, heterocysts, and akinetes 13. Classification of lake populations on the basis of range of cell size for vegetative cells, heterocysts, and akinetes 14. Comparison of range of variation of cell size in the study populations and Komarek's populations (microns) 15. Published taxa of hahanizomenon (Group I probably taxa, Group 11 taxa distinguished by end-cell shape, Group III questionable taxa) vii LIST OF FIGURES 1. Diagram of kohanizomensm_llgazagmft filament 2. Map of Lake Minnetonka (Halsted and Carman Bay) 3. Hypsograph (depth-area curve) of Halsted Bay 4. Orthophosphate, nitrate, and ammonia concentrations in Halsted Bay during 1972 5. Orthophosphate, nitrate, and ammonia concentrations in Carman Bay during 1972 6. Map of Itasca State Park (Spencer Pond, Squaw Lake, Elk Lake 7. Hypsograph (depth-area curve) of Spencer Pond 8. Categories for cell shapes and end cell contents 9. Seasonal change in Aphanizomenon cell concentration per M2 in Halsted Bay for 1971, 1972, and 1974 10. Seasonal change in specific rate of change per day for Aphanizomenon cell concentrations per rilz in Halsted Bay for 1971, 1972, and 1974 11. Isopleths of filament concentration, isopleths of temperature (0c), and Sec chi disc depths for 1971 in Halsted Bay 12. Isopleths of filament concentration, isopleths of temperature (0C), and Secchi disc depths for 1972 in Halsted Bay 13. Isopleths of filament concentration and temperature (0c) for 1974 in Halsted Bay 14. Seasonal change of phytoplankton concentration other than A hanizomenon (blue-green algae, green algae, diatoms) for 1974 in Halsted Bay 15. Seasonal change in Aplanimmlnan filament concentration per M2 in Carman Bay for 1971 and 1972 16. Seasonal change in specific rate of change per day for Aphankpm-n.n filament concentration per M4 in Carman Bay for 1971 and 1972 17. Isopleths of filament concentration, isopleths of temperature (°C), and Secchi dipc depth in Carman Bay for 1971 viii 18. Isopleths of filament concentration, isopleths of temperature (°C), and Secchi disc depth in Carman Bay for 1972 19. Seasonal change in ARLIAniammn filament concen- tration per in Spencer Pond for 1969, 1971, and 1972 20. Seasonal change in specific rate of change per day for Aphanizomenon filament concentration per M2 in Spencer Pond for 1969, 1971, and 1972 21. Isopleths of filament concentration? temperature (0C), and oxygen concentration (ppm) in Spencer Pond for 1969 22. Depth profiles of percent maximum Aphanizomenw, filament concentration, temperature (0C), and oxygen concentration (ppm) in Squaw Lake during 1969 23. Depth profiles of percent maximum Aphanizomenon filament concentration, temperature (0C), and oxygen concentration (ppm) in Elk Lake during 1969 24. Seasonal change of heterRcyst, akinete, and end cell concentration per M4 in Halsted Bay for 1971, 1972, and 1974 25. Seasonal variation in percent vegetative cells, end cells, heterocysts, and akinetes in Halsted Bay for 1971, 1972, and 1974 26. Seasonal change of heterocyst and akinete concentration per M2 in Carman Bay for 1971 and 1972 27. Seasonal change of heterocyst and akinete concentration per M2 in Spencer Pond for 1969, 1971, and 1972 28. Nitrogen fixation (acetylene reduction) by net con- centrated plankton in Halsted Bay for 1972 • 29. Frequency polygons, mean, and standard