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Effects of Some Abiotic and Biotic Factors on the Zooplankton Community in Lake Baringo, Kenya

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Effects of Some Abiotic and Biotic Factors on the Zooplankton Community in Lake Baringo, Kenya EFFECTS OF SOME ABIOTIC AND BIOTIC FACTORS ON THE ZOOPLANKTON COMMUNITY IN LAKE BARINGO, KENYA Omondi Reuben A Thesis submitted to the Graduate School in Partial Fulfillment for the Requirements of the award of a Doctor of Philosophy Degree in Limnology of Egerton University EGERTON UNIVERSITY OCTOBER 2014 i DECLARATION AND RECOMMENDATION DECLARATION This thesis is my original work and has not been submitted or presented for examination in any institution. Reuben Omondi (SD17/0238/09) Signature:……………………… Date:………………………………. RECOMMENDATION This thesis has been submitted for examination with our approval as University Supervisors. Associate Professor Adiel M. Magana Faculty of Science and Technology Chuka University Signature:…………………….. Date:…………………………… Associate Professor Andrew W. Yasindi Department of Biological Sciences Egerton University Signature:………………………… Date:……………………………. ii COPYRIGHT © 2014, Reuben Omondi No part of this thesis may be reproduced in part or full, stored in any retrieval system, or transmitted in any form or means (electronic, mechanical, photocopying, recording or otherwise) except for short extracts with acknowledgement, without prior written permission of the author or Egerton University on behalf of the author. All rights reserved iii ACKNOWLEDGEMENTS I wish to express my sincere gratitude to my supervisors Professor Adiel Magana and Professor Andrew Yasindi for their guidance and encouragement during the study. I am grateful to the technical staff of Kenya Marine and Fisheries Research Institute, Baringo and Kisumu centres for their assistance in the field and laboratory. I especially thank Dick Owage who travelled with me to Baringo from Kisumu every month for sampling and coxswain Benjamin Arwaita who ably piloted us in Lake Baringo during the study including over the 24 hour sampling exercises. Lewis Mungai was also very helpful in the laboratory at Egerton University and Alfred Burian who assisted in rotifer identification. The study could not have been possible without the support of Egerton University and my employer Kenya Marine and Fisheries Research Institute to whom I am greatly indebted. This study was supported by the grants from the National Council of Science and Technology (Grant number NCST5/003/Postgraduate/03) whom I thank. Lastly, I want to thank my wife Lilian, children Ann and Job for their love and understanding, and to many relatives and friends some of whom did not know what I was up to. iv ABSTRACT Lake Baringo is a turbid lake that lies in a closed drainage basin of the Kenyan East African Rift Valley. The lake’s water quality has deteriorated in the recent past mainly due to sedimentation from its catchment arising from poor agricultural practices, deforestion and overgrazing. Its fishery has also declined since the 1980s and frequent lake closures to fishing activities have not alleviated the problem. This shows that there may be other critical ecological and environmental factors affecting the ecosystem. To understand problems facing the lake, there is need for well-coordinated and comprehensive ecological investigations considering the complexity of the ecosystem. Zooplankton is important in energy transfer from primary producers and constitute a significant component of the diets of the juveniles and some adults of many fish species. The objective of the present study was to determine the effect of some physical, chemical and biological factors on the spatial and temporal distribution, abundance and biomass of zooplankton in Lake Baringo. Stratified random design was used to allow for statistical comparison between zooplankton abundance and biomass at different stations and months with environmental factors using Analysis of Variance (ANOVA). The relatively stable environmental factors across the sampling stations in the lake were attributed to its small size, shallowness and the daily mixing by wind action. A total of 39 species of zooplankton belonging to Rotifera, Cladocera and Copepoda groups were recorded. The results indicate that distribution, diversity, abundance and biomass of zooplankton were influenced by environmental factors especially depth, conductivity and turbidity. Diel vertical distribution of zooplankton was the reverse of what is reported from clear lakes with organisms congregating to the surface during the day and descending to the bottom at night. Investigations into the diet of three main fish species in the lake showed that Oreochromis niloticus baringoensis mostly depended on algae, Clarias gariepinus depended on fish while Protopterus aethiopicus thrives on molluscs as their dominant food. The growth performance of the once dominant endemic fish, O. niloticus baringoensis could be affected by the high turbidity, which reduces primary production. Moreover, reduced clarity hampers the feeding success of this visual feeding fish and has decreased macrophytes to near extinction. There is urgent need for rehabilitation of Lake Baringo and the study recommend afforestation and reduction of livestock numbers in the catchment as some of the ways of reducing soil erosion and sediment input in the lake. The results of the study may be used as an important tool for the detection of stability and trophic levels of the ecosystem and to provide data for models on maximal resource production of the lake. v TABLE OF CONTENT DECLARATION AND RECOMMENDATION ...................................................................... ii COPYRIGHT ........................................................................................................................... iii ACKNOWLEDGEMENTS ...................................................................................................... iv ABSTRACT ............................................................................................................................... v TABLE OF CONTENT ............................................................................................................ vi LIST OF FIGURES .................................................................................................................. ix LIST OF TABLES ................................................................................................................... xii LIST OF PLATES ................................................................................................................. xiii LIST OF APPENDICES ......................................................................................................... xiv LIST OF ABBREVIATIONS AND ACRONYMS ................................................................ xv DEFINITION OF TERMS ..................................................................................................... xvi CHAPTER ONE ...................................................................................................................... 1 1.0 GENERAL INTRODUCTION ........................................................................................ 1 1.1 Introduction ...................................................................................................................... 1 1.2 Statement of the problem ................................................................................................. 2 1.3 Objectives ........................................................................................................................ 3 1.3.1 General objective: ..................................................................................................... 3 1.3.2 Specific objectives: ................................................................................................... 3 1.4 Hypotheses ....................................................................................................................... 3 1.5 Justification ...................................................................................................................... 4 1.6 The scope and limitations of the study ............................................................................ 4 1.7 Thesis format ................................................................................................................... 5 1.8 References ........................................................................................................................ 7 CHAPTER TWO ..................................................................................................................... 9 2.0 LITERATURE REVIEW ................................................................................................ 9 2.1 Formation of Rift Valley and Lake Baringo .................................................................... 9 2.2 Physico-chemical factors ............................................................................................... 10 2.3 Biological factors ........................................................................................................... 11 2.4 Relationship between physico-chemical and biological factors .................................... 13 2.5 Lake Baringo catchment activities ................................................................................. 16 2.6 References ...................................................................................................................... 18 CHAPTER THREE ............................................................................................................... 24 3.0 PHYSICO-CHEMICAL FACTORS AND CHLOROPHYLL A IN LAKE BARINGO .............................................................................................................................................
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