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The Influence of Salinity on Various Life Stages of Ruppia Tuberosa and Implications for Its Distribution in the Coorong, South Australia

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The Influence of Salinity on Various Life Stages of Ruppia Tuberosa and Implications for Its Distribution in the Coorong, South Australia The Influence of Salinity on Various Life Stages of Ruppia tuberosa and implications for its distribution in the Coorong, South Australia by Dae Heui Kim School of Earth and Environmental Sciences, The University of Adelaide A thesis submitted to The University of Adelaide for the degree of Doctor of Philosophy November 2013 Table of Contents i Table of Contents Table of Contents ............................................................................................................. i List of Tables ................................................................................................................... v List of Figures ................................................................................................................ vii Abstract ................................................................................................................... x Declaration of Originality............................................................................................ xiv Foreword ................................................................................................................. xv Publications Associated with this thesis ..................................................................... xvi Acknowledgements ........................................................................................................ xx Chapter 1 General Introduction............................................................................... 1 1.1 The salinisation of aquatic ecosystems ............................................................... 1 1.2 Impacts of salinisation on aquatic macrophyte communities .............................. 2 1.2.1 Germination response to salinisation ................................................................ 2 1.2.2 Physiological and growth responses to salinisation .......................................... 3 1.3 The importance of water regime on aquatic macrophytes ................................... 4 1.4 Ecological importance of halophyte of Ruppia ................................................... 5 1.4.1 Description of Ruppia ....................................................................................... 5 1.4.2 Classification of Ruppia ................................................................................... 5 1.4.3 Distribution of Ruppia ...................................................................................... 6 1.4.4 Life-cycle of Ruppia ......................................................................................... 6 1.5 Ruppia populations in the Coorong region.......................................................... 9 1.5.1 Study area: The Coorong region of southern Australia .................................... 9 1.5.2 Distribution of Ruppia tuberosa in response to salinity and water depth in the Coorong region ................................................................................................. 12 1.5.3 Germination of Ruppia tuberosa and Ruppia megacarpa response to salinity .. ........................................................................................................................ 13 1.5.4 The effect of salinity on growth and reproduction of Ruppia tuberosa .......... 13 1.5.5 The effect of salinity on photosynthesis of Ruppia tuberosa ......................... 14 ii Table of Contents Chapter 2 How Ruppia tuberosa’s Life cycle is adapted to contrasting habitats ... ................................................................................................................. 15 2.1 Introduction ....................................................................................................... 15 2.2 Meterial and methods ........................................................................................ 16 2.2.1 Site description ............................................................................................... 16 2.2.2 Field surveys ................................................................................................... 18 2.2.3 Statistical analyses .......................................................................................... 20 2.3 Results ............................................................................................................... 20 2.3.1 Salinity changes .............................................................................................. 20 2.3.2 Shoot abundance ............................................................................................. 21 2.3.3 Flower abundance ........................................................................................... 24 2.3.4 Seed abundance .............................................................................................. 25 2.3.5 Turion abundance ........................................................................................... 26 2.4 Discussion ......................................................................................................... 27 2.4.1 How Ruppia tuberosa’s life cycle is adapted to different habitats ................. 28 2.4.2 Management implication for the restoration of Ruppia .................................. 32 Chapter 3 The effect of salinity on the germination of Ruppia tuberosa and Ruppia megacarpa and implications for the Coorong ................................................ 33 3.1 Introduction ....................................................................................................... 33 3.2 Material and methods ........................................................................................ 34 3.2.1 Site description ............................................................................................... 34 3.2.2 Seed and turion collection and storage ........................................................... 36 3.2.3 Experimental design and procedure ................................................................ 36 3.2.4 propagule (seed and turion) viability test ....................................................... 38 3.2.5 Statistical analyses .......................................................................................... 39 3.2.6 Mapping the probability of germination in the Coorong ................................ 40 3.3 Results ............................................................................................................... 40 3.3.1 Effects of salinity and sediment on germination ............................................ 40 3.3.2 Effect of transfer from high to low salinity .................................................... 43 3.3.3 Effects of salinity on imbibition and Na concentrations of seeds ................... 44 3.3.4 The probability of germination of Ruppia in the Coorong ............................. 47 3.4 Discussion ......................................................................................................... 49 3.4.1 Effects of salinity and sediment on germination ............................................ 49 3.4.2 Effect of transfer form high to low salinity .................................................... 50 3.4.3 Effects of salinity on imbibition and Na concentrations of seeds ................... 50 3.4.4 Summary of Ruppia tuberosa and Ruppia megacarpa germination .............. 51 Table of Contents iii 3.4.5 Implications for the Coorong .......................................................................... 51 Chapter 4 The effect of salinity on the growth and reproduction of Ruppia tuberosa ................................................................................................................. 53 4.1 Introduction ....................................................................................................... 53 4.2 Material and methods ........................................................................................ 55 4.2.1 Site description ............................................................................................... 55 4.2.2 Experimental design and procedure ................................................................ 56 4.2.3 Statistical analyses .......................................................................................... 59 4.3 Results ............................................................................................................... 59 4.3.1 Salinity and ion concentrations in Ruppia tuberosa tissues under pond conditions .......................................................................................................... 59 4.3.2 Growth of Ruppia tuberosa under pond conditions ........................................ 61 4.3.3 Effects of ion concentrations on the performance of pond grown Ruppia tuberosa ............................................................................................................ 63 4.3.4 Effects of ion concentrations in Ruppia tuberosa tissue in situ ...................... 64 4.3.5 Species performance of Ruppia tuberosa in situ ............................................ 65 4.4 Discussion ......................................................................................................... 65 4.4.1 The total biomass and relative growth rate in response to ion concentrations 65 4.4.2 Sexual reproduction in response to ion concentrations .................................. 66 4.4.3 Asexual reproduction in response to ion concentrations ................................ 67 4.4.4 Shoot length in response to ion concentrations .............................................. 68
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