SOME ASPECTS OF THE LIMNOLOGY OF KANDY LAKE, SRI LANKA Thesis submitted for the Degree of Master of Philosophy in the University of Kelaniya, Sri Lanka by Samaradiwakara Rajapaksha Mohottalalage Swamapali Samaradiwakara (B.Sc.) Institute of Fundamental Studies Hantana Road Kandy Sri Lanka December 2003 n I do hereby declare that the work reported in this thesis was exclusively carried out by me under the supervision of Professor E. I. L. Silva, Institute of Fundamental Studies, Kandy and Professor U. S. Amarasinghe, Department of Zoology, University of Kelaniya. It describes the results of my own independent research except where due reference has been made in the text. No part of this thesis has been submitted earlier or concurrently for the same or any other degree. ^tnz£res,' rCrC Date Signature of the candidate Certified by: 1 .Name and Signature of the supervisor: Date: 2.Name and Signature of the supervisor: Date: Ill Acknowledgements I am highly gratitude to my supervisor Prof. E. I. L. Silva, the Project Leader of Ecology and Environmental Biology Project, Institute of Fundamental Studies, Kandy, for his guiding and continuous encouragement throughout my study. Also I am very much appreciate the invaluable guidance, constructive comments of my internal supervisor Prof. U. S. Amarasinghe, Department of Zoology, University of Kelaniya. Without their untiring guidance, this thesis would not have become a reality. I would like to extend my gratitude to Prof. K. Thennakone, Director, IFS for permission granted to continue the work until completion of this thesis at IFS. I wish to thank the other members of IFS staff who offered their support in many ways and I regret that they could not be acknowledged here individually. I thank very much to Director, Upper Mahaweli Watershed Management Project, Dam site, Polgolla for providing me a land use map of the watershed area of Kandy Lake, and the Municipal Commissioner of Kandy for granting me permission to field sampling form Kandy Lake. My sincere thank goes to my husband Namal P. Athukorala for his continuous assistance in the field as well as laboratory analysis and all the other supports to make this effort success. I acknowledge the valuable contribution of Dr. IV (Ms) S. Nathanael for reading the draft and constructive comments with her busy schedule. I will never forget the kindnesses and helpfulness of Mrs. G.A.R.K. Gamlath, Ms. I. Thumpela, Mrs. T. Weligodapola, and Mrs. N. R. N. Silva in the laboratory work at IFS. My Special thank goes to Dr. (Mrs.) Yasantha Mapatuna, former Director (Acting) of the Department of National Museums, Colombo for her encouragement. My sincere thanks are also to Mr. C. Weerasinghe, Mr. R. Perera, Mrs. Manaram de Silva, Mr. Lalith Kariyawasam, Mr. S. Jayasekara and Mr. U. Rajapaksha for their kind support in computer works. I wish to thank Dr. C. Nissanka, Ms. T. Ariyananda, Mr. L. R. Wijepala and L. P. Mahinda for their moral support extended during this study. Finally, I take this opportunity to dedicate my special gratitude to my late beloved farther, my loving mother, my sisters and brothers and Mr. Sirimanna and family for their encouragements and fullest support in completing this task. To my beloved father and my loving mother and my teachers and to Viduni .i. VI Contents Declaration Acknowledgements Dedication Contents List of tables List of figures List of plates Abstract CHAPTER 1: INTRODUCTION 1.1 Freshwater 1.2 Water quality issues 1.2.1. Eutropbication 1.2.2. Organic and inorganic pollutants 1.2.3. Bioaccumulation and bio-magnification 1.2.4. Acidification 1.2.5. Salinization 1.2.6. Stream flow regulation 1.2.7. Sedimentation 1.3 Limnology VII 1.3.1 Limnology in the tropics 1.3.2 Limnology in Sri Lanka 1.4 Human interventions on inland water bodies 1.5 Kandy Lake 1.6 Objectives CHAPTER 2: MATERIALS AND METHODS 2.1. Study site 2.1.1 Physical settings 2.1.2. Morphology and hydrology 2.1.3 Watershed 2.2. Methods 2.2.1 Laboratory analysis 2.2.2 Phytoplankton primary productivity 2.2.3 Chlorophyll-a analysis 2.2.4 Phytoplankton composition 2.3. Data analysis CHAPTER 3: RESULTS 3.1 Physicochemical characteristics 3.1.1 Temperature 3.1.2 PH 3.1.3 Total alkalinity vm 3.1.5 Total suspended solids and turbidity 3.1.6 Dissolved oxygen 3.1.7 BOD5 3.1.8 Major cations and anion 3.1.9 Inter-relationships of physico-chemical characteristics 3.2 Nutrients 3.2.1. Dissolved phosphorous and total phosphorous 3.2.2. Nitrogen species 3.3 Photosynthesis and primary production 3.3.1 Light climate 3.3.2 Chlorophyll-a 3.3.3 Photosynthesis 3.3.4 Community respiration 3.3.5 Primary production 3.4 Phytoplankton community 3.4.1 Species composition and abundance of phytoplankton 3.4.2 Spatial distribution of phytoplankton community 3.4.3 Seasonal fluctuations of the plankton community 3.4.4 Phytoplankton species diversity 3.4.5 Vertical distribution of phytoplankton community CHAPTER 4: DISCUSSION 5 Conclusions 6. References X List of Tables No Content Page 3.1 Ranges and mean values (±SD) of physicochemical parameters of 48 surface and bottom waters of four sites for first 12 month period. 3.2 Results of one-way ANOVA for inter-site variation of 51 physicochemical characteristics of surface water for first 12 month period. 3.3 Results of one-way ANOVA for inter-site variation of 52 physicochemical characteristics of bottom waters for first 12 month period. 3.4 Results of Student's t-test for intra-site variation of physicochemical 53 parameters between surface and bottom waters at station A. 3.5 Relationships of independent and dependent physicochemical 67 parameters examined using least square model. 3.6 Results of one-way ANOVA for inter-site variation of micronutrients 72 in surface water of Kandy Lake during the study period. 3.7 Results of one-way ANOVA for inter-site variation of micronutrients 73 in bottom water of Kandy Lake during the study period. 3.8 Results of Student's t-test for intra-site variation of micronutrients 74 between surface and bottom water at site A of Kandy Lake during the study period. 3.9 Abbreviations used in the text. 80 XI 3.10 The mean total incoming radiation (TIR) and photosynthesis available radiation (PhAR) within the period of bottle suspension for photosynthetic experiment in Kandy Lake. 3.11 Photosynthetic characteristics and related parameters of Kandy Lake. 3.12 Phytoplankton species and their abundance. xn List of Figures No Content Page 2.1 Location and bathymetry map of Kandy Lake and sampling 32 stations. 2.2 Landuse map of the watershed of Kandy Lake. 37 3.1 Monthly variation of water temperature during the study period. 54 3.2 Temperature profile at station A of Kandy Lake. 55 3.3 Monthly variation of pH, Electrical conductivity and total alkalinity 57 of surface and bottom water at site A. 3.4 Mean values of total suspended solids and turbidity of surface 60 water in Kandy Lake in to relation low, moderate and high rainfall seasons. 3.5 Monthly mean values of turbidity of surface water in Kandy Lake 60 during the study period. 3.6 Vertical distribution of dissolved oxygen concentration in Kandy 62 Lake during the study period. 3.7 Monthly variation of dissolved oxygen concentration in surface and 62 bottom water at site A. 3.8 Monthly variation of BOD5 in surface and bottom water at site A of 63 Kandy Lake. 3.9 Maucha's diagram to illustrate the relative ionic proportions of 65 XIII major cations and anions in Kandy Lake. 3.10 Scatter plots of interrelationships of physico-chemical parameters. 66 3.11 (a) Monthly variation of dissolved phosphorous and (b) monthly 70 variation of total phosphorous in surface and bottom water of Kandy Lake during the study period. 3.12 Monthly variation of NO 2 - N, NO 3 - N and NH4 - N in the surface 76 and bottom water at station A of Kandy Lake during the study period. 3.13 Scatter diagram of NH4 - N concentration vs Dissolved Oxygen in 78 the bottom water of site A of Kandy Lake. 3.14 The mean photosynthetically available radiation (PhAR) during 82 incubation for photosynthetic experiments in Kandy Lake. 3.15 Monthly mean percentage of the total incoming radiation (TIR %) 82 during incubation. 3.16 Monthly mean values of Secchi depth (ZSD) of the Kandy Lake 84 during the study period. 3.17 Monthly fluctuation of compensation depth (Zc) at site A of Kandy 84 Lake during the photosynthetic experiments. 3.18 Monthly values of Chlorophyll-a concentration in surface and 86 bottom water at site A of Kandy Lake for a period of two consecutive years. 3.19 Scatter diagram of Secchi depth vs chlorophyll-a concentration of 86 surface water at site A of Kandy Lake during the dry and lower rainy months. XIV 3.20 Relationship between total phosphorous and log chlorophyll-a 87 values of Kandy Lake during the study. 3.21 Depth profile of overall mean Chlorophyll-a concentrations of 88 Kandy Lake at site A. 3.22 Depth profiles of photosynthesis and community respiration during 90 the study period. 3.23 Monthly variation of Amax and 0 of Kandy Lake during the study 92 period. 3.24 Scatter diagrams of (a) Amax vs chlorophyll - a and (b) log a vs 92 chlorophyll-a. 3.25 Monthly variation of Chlorophyll-a at the depth of the A max and 0 93 max of Kandy Lake during the study period.