The Ecology of Salt Lake Hydrophytes: the Synecology of Saline
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tólrol8o THE ECOLOGY OF SALT LAKE HYDROPHYTES: THE SYNECOLOGY OF SALINE ECOSYSTEMS AND THE AUTECOLOGY OF THE GENUS RUPPTA L. IN THE SOUTH.EAST OF SOUTH AUSTRALIA MARGAREf ANNE BROCK B.Sc. (A.N.u.) DEPARTMENT OF ZOOLOGY TIIE UNIVERSITY OF ADELAIDE A thesis submitted Èo the University of Adelaide in fulfilment of the requirements for the degree of Doctor of PhilosoPhY DECEMBER 1979 Èrn¡qro,tCI t1{[ i'tì;' \ìI i'iw I \J "For there are some plants which cannot live except in wet; and again these are distinguished f::om one another by their fondness for different kinds of wetness; so that some grow in marshes, others in lakes, others in rivers, others even in the sea tt Theophrastus (370-c. 285 B.C") tEnquiry into Plantsl CONTENTS Page SUMMARY I DECI,ARATION l_l-r ACKNOVÍLEDGEMENTS l_v SECTION I INTRODUCTTON AND LITERATURE SURVEY Chapter 1 INTRODUCTION 1 Chapter 2 PREVIOUS STUDIES 4 2.1 Saline ecosystems 4 2. 2 Vascular hydrophytes B 2.3 fnland aquatic ecosystems of south-eastern South Australia I3 SECTION II SYNECOLOGICAT SURVEY OF TTIE SOUTH-EAST OF SOUTIT AUSTRALIA chapter 3 STUDY SITES AND ENVIRONIVIENTAL VARTABLES: SELECTION AND DESCRTPTION 19 3.1 Selection of determinants and sites 19 3.2 Salinity terminologY 20 3.3 Details of sites 2l 3.4 The major study area: Little Dip Conservation Park 27 Chapter 4 METHODS 2A 4.1 General sampling methods 2A 4.2 PartLcular sampling methods for three localities in the Little Dip Conservation Park: Little Dip Lake, Fresh Dip Lake and Lake ELj-za SaIt Marsh 32 4.3 Comparison of species composition a¡d vegetation associations of the three ecosystems 4T Chapter 5 SYNECOLOGICAI RESULTS: DATA AND INTERPRETATION 42 5.1 AII sites 42 1. General descriptions 42 2. Environrnental data 42 3. Vegetation data 48 Page 5.2 Little Dip Conservation Park 52 1. Little Dip Lake and Fresh Dip Lake 52 2. Lake Eliza SaIt Marsh: vegetation survey 54 Chapter 6 DISCUSSION OF SYNECOLOGÍCAL RESULTS 64 SECTTON rIr AUTECOLOGTCAL STUDY OF THE GENUS RUPPTA Chapter 7 OB.]ECTIVES 73 Chapter I SYSTEMATIC STUDTES 75 8.1 Previous studies 75 I. Taxa of Ruppia 75 2. Taxonomic critería 78 8.2 Ruppia in the south-east of South Australia 83 t. Introduction 83 2. Descriptions 84 3. Methods and data 87 8.3 Analysis of taxonomic characters 94 8.4 Nomenclature 100 8.5 Key to Ruppía in the south-east of South Australia 104 Chapter 9 ECOLOGICAL STUDTES 106 9.1 Introduction 106 9.2 Growth experiments 106 1. Field tr:ansplantation trial 106 2. Laboratory growth trials 108 9.3 Physiological experiments 11r 1. Germination a¡d d-ormancy 111 2. Salinity t20 3. Osmoregulation T2L 9.4 Population dynanics: life cycle patberns L28 1. Dry weight of- Ruppía compared with total plant parts ancl total organic matter r30 2. Dry weights of roots, rhizomes, Ieaves ancl reproductive parts in annual and perenni.al Ruppia popul.ations I31 Page 3 Changes in the structure of ,R. tuberosa and R. megacatpa popuLations along a transecÈ in water of decreasing depth 131 4 Seasonal changes of total dry weight of. Ruppia and of the proportions of parts for the three species L32 9.5 Reproductive biology 134 I- Seeds 134 2. Vegetative spread by rhizomes and shoots from nodes L34 3. Asexual perennating organs (turions) 135 4. Reproductive patterns 139 Chapter 10 CONCLUSTONS 148 APPENDTCES Appendix I Charact-eristics of sites not sampled regularly 155 Appendix Ir Lake conductivities and saliniti-es r56 Appendix IIf Lake chemistry of South Australian salt lakes L57 Appendix IV Plant list from saline lakes and surrounds of the Coorong and south-east of South Australia 158 Appendix V Glossary of terms used in the description of Ruppía 166 Appendix VI Characters examined for three forms of Ruppía from eighteen habitats L67 Appendix VII Quantitative measurements for twelve characters of Ruppia 168 Appendix VIII Leaf cell characters T7I Appendix IX Pollen grain length, width and shape for Ruppía from taxa A, B and C t72 Appendix X Method for preparing chromosome squash preparations of Ruppia L74 Appendix XI Summary of characters examined for Ruppia taxa A, B and C 175 Page Appendix XII Summary of twelve measured characters of Ruppia for iaxa A, B and C L76 Appendix XIII Tabulation of characters of described species of Ruppía r77 Appendix XIV l4easurements of proline concentration in Rttppia r78 BIBLIOGRAPHY 179 rrl SLTM¡,IARY The nature and distribution of submerged and emergent macro- phytes in relation to salinity, to the temporary or permanent nature of the aquatic habitats and to the tolerance of fluctuating environments was investigated in a series of saline ecosystems in the Coorong and Robe/Beachport areas of the south-east of South Austral-ia. A synecological survey of the floral- relationships in a range of saline habitats was foll-owed by an autecologicat study of. Ruppia t., a genus of submerged halophytes. OnIy two genera of angiosperms occur above a salinity of o/oo o,/oo 4 TDSz Rt'Lpp'ía is found in waters from 3 to 230 TDS and o/oo LepiLaern Drumm. ex Harvey from 3 to 50 tOS. Both occur in permanent and ephemeral ha-bitats, in pure and mixed stands and in the u¡derstorey of emergent salt marsh communities. The plant associations of a salt marsh, a saline lake and a fresh lake were compared by means of morphometric and vegetation maps and quadrat and biomass sampling. For the Lake Eliza Salt Marsh community twelve pì-ant associations were delimited by species composition, and mapping of these associations shows that their distribution is related to small increases in efevation, which total 0.5 m height above the lake l-evel- over 500 m distance from the shore. Annual and perennial growth forms of Ruppia were observed and the genetii or ecological bases of these growth form differences were examined further. A systematic survey indicated the presence of three species, two annuals, RuppiA tttbenOsa Davis and Tomlinson and, Ruppiq. poLucØ'pa Mason, and one perennial, Rlppia mega'ca.r'pa Mason, none of v¡hich has previously been recognised in South Àustrafia. Both annuaÌ species have asexual perennating organs (turions) t .structures that have not been recorded for this genus outside Australia - Transplantation, germination and salinity experiments were used to examine the differences between annual and perennial growth forms. The wide salinity tolerance of all three species v¡as con- firmed. Under experimental conditions annual and perennial growth forms did not alter in alternate habitats. Decrease in salinity had a positive effect on the germination of the perennial .R. mega'carpa whereas increase ín salinity and the wetting and drying of seeds broke the dormancy of the annual .R. tubez'osa seeds. Explanations advanced to exptain the ability of this species to withsta¡d harsh and fluctuating environments were examined by analyses of life cycles, reproductive patterns and osmoregulatory mechanisms of the three species of. Ruppia l-rL DECLARATION This thesis contains no material wh\-ch has been accepted for the award of any other degree or diploma in any university and, to the best of my knowledge and belief, contains no material previously pr:blished or written by another person, except where due reference is made in the text. turþ ,/1"¿ ( '.+ t_v. ACKNOVTLEDGEMENTS I thank Professor V¡.D. Williams for the opportunity to under- take this study, for the use of facilities in the Department of ZooLogy and for his supervision of this project. Such an ecological - and botanical - study would certainly not have been possible without the help of experts in many fields and the use of facilities in other departments a¡d institutions. I thank, most sincerely, all those people who have helped in discussions and with practical matters; j-n particular f acknowledge - taxonomic d-iscussions with Drs S. Jacobs (National Herbarium of New South lrlales) and J. Jessop (fhe State Herbarium of South Australia) and the help of The State Herbarium of South Austratia in the identification of plants, - anatomical discussions with Moira Robinson and the use of the r{ax-sectioning facilities in the Department of Botany, - Dr D. Aspinall (Department of P1ant Physiology, lrfaite Agrícultura1 Research Institute) for the use of facilities for proline analysis, and Gerard Faber for patiently teaching me the techniques, - the X-ray diffractometer analysis of sediment samples by John Warren (Flinders University), - the use of surveying eguipment from the Department of Civil Engineering and the help of Andrew Close with t}le field surveying, - the constructÍon of field and Ia-boratory egui¡.rment by Terry MacKenzie. In the preparation of the thesis, credit is due to Julie Francis for the competently-prepared final drafts of figures, to Peter Kl.opotowski (F1inders Medical Centre) and PhiIlip Kempster for their invaluabl-e assistance with the photography and to Maggie Fisher for her patience in the arduous taslc of converting my copy to a professional typescript. I also tha¡k the secretarial staff of the Department of Zoology for typing the final draft of Chapters l- to 4 and the text- of Chapter 5. v. The continued, encouragement and co.m¡nents of Drs John Bishop (ex University of Adelaide) and Brian Moss (University of East Anglia) throughout arl stages of this study saved me from many a disastrous decision. AIl my friends must take for their and encouragement, "tä¿it help especiarry on fierd trips and in the preparation of this thesis: r thank particularly Alice fùel1s, Carol McKenzie and Maggie Fisher and arr the 'fierd workers' who hetped me enjoy the evenings around the campfire in the Little Dip Conservation park.