ECOLOGICAL STUDY OF THE MOLLUSCAN FAUNA ON INTERTIDAL ARTIFICIAL ROCKY SHORE OF TARKWA BAY AREA, LAGOS, NIGERIA BY ERUTEYA, ONOSIVBAKPO JONATHAN ` FEBRUARY 2014 II ECOLOGICAL STUDY OF THE MOLLUSCAN FAUNA ON INTERTIDAL ARTIFICIAL ROCKY SHORE OF TARKWA BAY AREA, LAGOS, NIGERIA A thesis submitted for the degree of Doctor of Philosophy (Marine Biology) BY ERUTEYA, ONOSIVBAKPO JONATHAN B.Sc, M.Sc (Zoology) Lagos. MATRIC NO: 830809031 DEPARTMENT OF MARINE SCIENCES III IV DEDICATION This project is dedicated to Almighty God for His divine guidance over my life, and members of my immediate family. V ACKNOWLEDGEMENTS I am indeed grateful for the help and supports I received from numerous people in various institutions during the course of this project. Firstly, I would like to thank my supervisors: Associate Professor Clement Aghatise Edokpayi for his kindness, thoughtfulness, sense of humour and generous support, which made the work for this study more pleasurable. His sharing of ideas has been and will, hopefully, continue to be one of my most enjoyable experiences. Again, I would also like to thank my second supervisor, Associate Professor J. K Saliu, who also supervised my M.Sc. thesis. Both of them have supported me throughout, and provided me with sound advice and opportunities that broaden my horizon. I would like to thank Professors: K. K Ikusemiju, D. I. Nwankwo, Rosemary Egonmwan, and L. O. Chukwu for their generous supports, for editing of my thesis, award of Graduate Fellow Scholarship and provisions of scientific journals. They have also continually showed immense optimism and unswerving faith in my abilities. Thanks to Dr (Mrs) A.O. Osibona, Dr S.O. Ayoola, Dr A.A Otitoloju, Dr A. Z. Aderolu, Dr (Mrs) A. O. Lawal-Are, Dr M. P. Kuton, Dr I. C. Onyema, Dr Efe Uwadia, Dr M O Lawal and Dr Segun for their friendly supports and encouragement. I would also like to thank the non-teaching staff: Mrs Olutimilehin, Mr Lawal, Mr Coker (Marine Sciences) and Mr Bengusa (Chemistry Department), Mr Uncle B, a retired Laboratory Technologist (Zoology Department). I, also extend my appreciation to my fellow Ph.D students: especially Mr Joseph Nkwoji, and Mr Uzoh (Marine sciences) for their moral support. VI Finally, I would also like to extend my appreciation to all members of my family, more importantly my children (Emmanuel, Josephine and Deborah), they are wonderful team. I cherish their faith in me. I also cherish the love and support of my wife, Mrs Eunice Esther Eruteya, during the course of this project. This thesis is dedicated to her and my children. Above all, I thank the Almighty God for His strength and Mercy upon my life without which I can do nothing (Luke 1:37). VII TABLE OF CONTENTS CONTENTS PAGES CERTIFICATION………………………………………………………………………. .II DEDICATION…………………………………………………………………………... 11I ACKNOWLEDGEMENTS……………………………………………………………….1V TABLE OF CONTENTS………………………………………………………………….V1 LIST OF TABLES……………………………………………………………………......XIV LIST OF FIGURES…………………………………………………………………….XV1II LIST OF PLATES……………………………………………………………………..XX111 LIST OF APPENDICES…………………………………………………………………XXV OPERATIONAL DEFINITION OF TERMS…………………………………………XXXII LIST OF ABBREVIATIONS…………………………………………………………XXXIII ABSTRACT…………………………………………………………………………...XXXIV CHAPTER ONE I.0 INTRODUCTION…………………………………………………………………..1 1. I BACKGROUND OF THE STUDY…………………………………………..1 1. 2 STATEMENT OF PROBLEM……………………………………………….5 1. 3 AIM AND SPECIFIC OBJECTIVES OF STUDY……………………...........6 1. 4 SIGNIFICANCE OF THE STUDY…………………………………………..7 1. 5 RESEARCH QUESTIONS………………………………………………........8 VIII CHAPTER TWO 2. 0 LITERATURE REVIEW………………………………………………………….9 2. 1 PHYSICO-CHEMICAL CHARACTERISTICS……………………………..9 2. 2 ROCKY SHORES: ENVIRONMENTAL CONDITIONS………………….11 2. 3 MOLLUSCAN COMMUNITIES AND ADAPTATIONS……………….....11 2. 4 INVERTEBRATE COMMUNITIES OF LAGOS HABOUR AND GULF OF GUINEA………………………………………………………….12 2.5 BIOLOGY OF INTERTIDAL MOLLUSCS………………………………..13 2.5.1 Feeding………………………………………………….….…….13 2.5.2 Gut Content Analyses……………………………………….........13 2.5.3 Growth of Intertidal Molluscs…………………………………...14 2.5.4 Heavy metal concentrations: seawaters, seaweeds and and selected molluscs……………………………………………16 2.5.5 Reproduction in intertidal molluscs…………………………….18 2.6 EFFECT OF PHYSICAL AND PHYSIOLOGICAL STRESS ON THE DISTRIBUTION OF INTERTIDAL MOLLUSCS…………………...19 2.6.1 Effect of sea surface temperature (SST) on intertidal molluscs………………………………………………………….21 2.6.2 Ecological Implications of shore Height on molluscs…….……..22 2.6.3 Ecological Effects of Shell Size and Shape of Intertidal molluscs……………………………………………………..........24 2.6.4 Ecological Implications of molluscan faunal shell IX colours…………………………………………………………...25 2.6.5 Economic Importance of Intertidal Molluscs……………………26 2.6.6 Strategies for molluscan conservation and sustainable utilization………………………………………………………….29 CHAPTER THREE 3.0 MATERIALS AND METHODS……………………………………………………31 3.1 DESCRIPTION OF THE STUDY AREA……………………………………..31 3.1.1 West mole………………………………………………………………33 3.1.2 Training mole……………………………………..................................35 3.1.3 East mole………………………………………………………………37 3.2 SAMPLING DESIGN………………………………………………………….39 3.2.1 Site selections………………………………………………………...39 3.2.2 Collection of seawater………………………………………………...44 3.2.3 Collection of algal samples…………………………………………...44 3.2.4 Collection of molluscan samples……………………………………..44 3.2.5 Choice of study species………………………………………………..45 3.2.6 Sample preservations………………………………………………….46 3.3 SAMPLE ANALYSES……………………………………………………………46 3.3.1 Water analyses………………………………………………………....46 3.3.2 Air and Water Temperatures…………………………………….…….46 X 3.3.3 Rock Temperature…………………………………………………......46 3.3.4 Salinity……………………………………………………………........46 3.3.5 Dissolved Oxygen (DO)…………………………….………………….46 3.3.6 Rainfall Data…………………………………………………………...47 3.4 LABORATORY ANALYSIS………………………..…………………………..47 3.4.1 Nutrient Analyses…………………………………………………....47 3.4.2 Heavy metal analysis………………………………………………..47 3.5 STUDIES ON THE BIOLOGY OF INTERTIDAL MOLLUSCS…………. …48 3.5.1 Feeding in selected intertidal molluscan species…………. ………...48 3.5.2 Foraging behaviours of intertidal molluscs………… ………………...48 3.5.3 Gut Content Analysis……………… ………………………………....49 3.5.4 Comparative studies on growth of selected molluscan species at three different tidal zones…………………………………………………...49 3.5.5 Determination of wet, dry biomass and Ash-free Dry- Weight (AFDW)………………………………………………………50 3.5.6 Effects of interspecific competition on molluscs’ growth rate in the laboratory………………………………………………………50 3.5.7 Studies on shell dimensions of selected molluscs……………………51 3.5.8 Studies on the reproductive biology of selected molluscs………….....51 3.5.8.1 Gonadosomatic Index (GSI)……………………….....52 3.5.8.2 Reproductive Effort (R.F)……………….…………….53 3.5.8.3 Histology of the gonads of selected molluscs….. …53 XI 3.5.8.4 Sex Ratios…………………………………………….54 3.5.8.5 Size at first sexual maturity…………………………..54 3.6 Statistical Analysis……………………………………………………54 3.6.1 Molluscan Data analysis………………………………………………..55 CHAPTER FOUR 4. 0 RESULTS……………………………………………………………………………...57 4.1 PHYSICO-CHEMICAL CHARACTERISTICS OF TARKWA BAY…..57 4.1.1 Temperature……………………………………………………………………57 4.1.2 Salinity and Rainfall Patterns………………………………………………....67 4.1.3 Hydrogen Ion Concentration (pH)…………………………………..……….69 4.1.4 Dissolved Oxygen (DO)……………………………………………………..70 4.1.5 Biochemical Oxygen Demand (BOD)5………………………………… ….72 4.1.6 Chemical Oxygen Demand………………………………………………….74 4.1.7 Conductivity…………………………………………………………………76 4.1.8 Nutrients………………………….…………………………………………77 4.1.9 Heavy metals……………………………………………………………….80 4.2.0 ENVIRONMENTAL FLUCTUATIONS IN INTERTIDAL ROCK POOLS OF TARKWA BAY……………………………………..………82 4.2.I Thermohaline fluctuations in three different intertidal rock pools at Tarkwa Bay………………………….……..........82 4.2.2 Thermal variations in air, rock surface and limpet´s XII foot…………………………………………………………..85 4.3.0 HEAVY METAL STUDIES……………………………………………………...86 4.3.1 Heavy metal concentrations in seawaters, seaweeds, and selected molluscs…………………….…………………...87 4.3.2 Heavy metal concentrations in different body parts of molluscs……………………………………………..……….90 4.4.0 COMPOSITION, DISTRIBUTION, ABUNDANCE, DIVERSITY AND SEASONALITY OF MOLLUSCAN COMMUNITIES OF TARKWA BAY INTERTIDAL ROCKY SHORE……………………………………..…….108 4.5.0 UNIVARIATE ANALYSIS OF MOLLUSCAN ECOLOGY AT THREE MOLES OF TARKWA BAY……….....................................................................129 4.5.1 Shannon´s Index (H’)……………………………………………….........129 4.5.2 Pielou’ Evenness (J’)………………………………………….…............132 4.5.3 Simpson’ Dominance Index…………………………………………......135 4.5.4 Size- frequency distributions of selected molluscs…..…………………138 4.5.4.1 Patella safiana…………………………………………….....138 4.5.4.2 Nerita senegalensis………………………………………......138 4.5.4.3 Thais callifera…………………………………………………139 4.5.4.3 Buccinum undatum…………………………………………..139 4.6.0 BIOLOGY OF INTERTIDAL MOLLUSCS……………………………….…….145 4.6.1 Studies on shell dimensions on selected molluscs……………………145 4.6.2 Gut Content Analysis………………………………………………….168 XIII 4.6.3 Foraging behaviours of selected intertidal molluscs………………….170 4.6.4 Studies on molluscs’ growth at different tidal zones……. ………….172 4.6.5. Effects of intra-and interspecific competitions on growth rate of selected species at different environments………. ………..174 4.6.6 Growth rates between males, females and in comparison to a mixed sex molluscan populations……………………… .. …….175 4.7.0 BIOMASS STUDIES ON INTERTIDAL MOLLUSC OF ECONOMIC INTEREST……………………………………………………177 4.7.1 West mole: Wet Biomass studies………………………………….177