University of Wollongong Research Online University of Wollongong Thesis Collection 2017+ University of Wollongong Thesis Collections 2017 Pattern and process in a threatened seagrass community: dynamics and habitat use by sessile epifaunal invertebrates in Posidonia australis Marie-Claire A. Demers University of Wollongong Follow this and additional works at: https://ro.uow.edu.au/theses1 University of Wollongong Copyright Warning You may print or download ONE copy of this document for the purpose of your own research or study. The University does not authorise you to copy, communicate or otherwise make available electronically to any other person any copyright material contained on this site. You are reminded of the following: This work is copyright. Apart from any use permitted under the Copyright Act 1968, no part of this work may be reproduced by any process, nor may any other exclusive right be exercised, without the permission of the author. 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Recommended Citation Demers, Marie-Claire A., Pattern and process in a threatened seagrass community: dynamics and habitat use by sessile epifaunal invertebrates in Posidonia australis, Doctor of Philosophy thesis, School of Biological Sciences, University of Wollongong, 2017. https://ro.uow.edu.au/theses1/43 Research Online is the open access institutional repository for the University of Wollongong. For further information contact the UOW Library: [email protected] PATTERN AND PROCESS IN A THREATENED SEAGRASS COMMUNITY: DYNAMICS AND HABITAT USE BY SESSILE EPIFAUNAL INVERTEBRATES IN POSIDONIA AUSTRALIS A thesis submitted in fulfilment of the requirements for the award of the degree DOCTOR OF PHILOSOPHY from University of Wollongong by Marie-Claire A. Demers B Env Sc (Hons Class 1) Faculty of Science, Medicine and Health Department of Biological Sciences 2017 CERTIFICATION I, Marie-Claire Demers, declare that this thesis, submitted in fulfilment of the requirements for the award of Doctor of Philosophy, in the Department of Biological Sciences, Faculty of Science, Medicine and Health, University of Wollongong, is wholly my own work unless otherwise referenced or acknowledged. The document has not been submitted for qualifications at any other academic institution. Marie-Claire A. Demers 08 February 2017 i TABLE OF CONTENTS CERTIFICATION ................................................................................................................................ i TABLE OF CONTENTS ..................................................................................................................... ii LIST OF TABLES .............................................................................................................................. vi LIST OF FIGURES ............................................................................................................................ ix ABSTRACT ...................................................................................................................................... xv ACKNOWLEDGEMENTS ............................................................................................................ xviii CHAPTER 1 : General introduction ..................................................................................................... 1 1.1 Ecological role of sponge and ascidians .................................................................................. 2 1.2 Habitat bias ............................................................................................................................... 3 1.3 Seagrass importance and decline.............................................................................................. 4 1.4 Seagrass associated species and ecosystem function ............................................................... 5 1.4.1 Seagrass associated species .......................................................................................... 5 1.4.2 Seagrass ecosystem functioning ................................................................................... 6 1.5 Patterns and drivers of sessile epifaunal invertebrate distribution in seagrass meadows ........ 8 1.5.1 Factors driving sponge distribution .............................................................................. 8 1.5.2 Abiotic factors .............................................................................................................. 9 1.5.3 Biotic factors .............................................................................................................. 11 1.6 Species of interest................................................................................................................... 13 1.7 Aims and structure of this thesis ............................................................................................ 14 CHAPTER 2: Under the radar: Small-scale distributional patterns of sessile epifaunal invertebrates in the seagrass Posidonia australis. .............................................................................. 16 2.1 Abstract .................................................................................................................................. 17 2.2 Introduction ............................................................................................................................ 18 2.3 Materials and methods ........................................................................................................... 20 2.3.1 Study area, study species and sampling methodology ............................................... 20 2.3.2 Statistical analyses ...................................................................................................... 24 2.4 Results .................................................................................................................................... 25 2.4.1 Overall patterns of diversity and abundance .............................................................. 25 2.4.2 Patterns of abundance; individual taxa ....................................................................... 34 2.4.3 Substrata on which epifauna attached ........................................................................ 35 2.5 Discussion .............................................................................................................................. 39 2.5.1 Patterns of distribution ............................................................................................... 39 2.5.2 Substratum used for attachment and the impact of humans ....................................... 41 ii 2.6 Conclusions ............................................................................................................................ 42 CHAPTER 3 : Are pilot studies worth the trouble? A case study using recalcitrant organisms ........ 43 3.1 Abstract .................................................................................................................................. 44 3.2 Introduction ............................................................................................................................ 45 3.3 Materials and methods ........................................................................................................... 46 3.3.1 Pilot study ................................................................................................................... 46 3.3.2 Main study .................................................................................................................. 47 3.3.3 Sampling method ........................................................................................................ 47 3.3.4 Statistical analyses ...................................................................................................... 47 3.4 Results .................................................................................................................................... 49 3.4.1 Measures of diversity and abundance ........................................................................ 49 3.4.2 Assemblage composition ............................................................................................ 49 3.4.3 Variability among spatial scales ................................................................................. 53 3.5 Discussion .............................................................................................................................. 56 3.5.1 Effectiveness of the pilot study .................................................................................. 56 3.5.2 Limitations of the Pilot study ..................................................................................... 57 3.6 Conclusions ............................................................................................................................ 58 3.7 Appendix ...............................................................................................................................