Responses of ghost crabs and other scavengers to habitat modification of urban sandy beaches

350 words maximum: (PLEASE TYPE) Populations in coastal areas are growing at a rate far exceeding that of other areas, resulting in escalating pressures on coastal areas around the world. Sandy beaches make up over 70% of the world coastlines, comprising some of the most highly sought after areas for human activities. Consequently, sandy beaches are some of the most vulnerable habitats to the effects of urbanisation, with beaches now threatened by a wide range of anthropogenic practices. Ghost crabs are widely used as ecological indicators of ecosystem health on sandy beaches, but have rarely been studied on beaches within large urban centres. In this thesis, ghost crab burrow densities were used to assess human impacts on beaches in the highly urbanised estuary, Sydney Harbour. Across 38 beaches in the harbour, mechanical beach cleaning frequency was found to be the most influential predictor of ghost crab distributions in the area, with burrow counts reduced on the most frequently cleaned beaches and highest burrow counts found on beaches that were cleaned no more than three times per week. Mechanical cleaning was associated with the volume of wrack accumulated onshore, with frequently cleaned beaches supporting significantly lower volumes of wrack then beaches that were cleaned less frequently. To examine how organic subsidies on sandy beaches affect crab behaviour, I experimentally manipulated the availability of organic marine matter (wrack and carrion). Ghost crabs demonstrated no short term response to either subsidy (measured by the initiation of new burrows near food source), while vertebrate scavengers demonstrated a rapid response to carrion subsidies only. The presence of vertebrate scavengers in treatment plots reduced the fossorial behaviour of ghost crabs, suggesting biological interactions among invertebrates and vertebrates. The arrival of marine subsidies to sandy beaches facilitates the exchange of resources between the marine and terrestrial zone. Given that these systems can rely heavily on this resource exchange any alteration in the natural supply of organic marine matter, e.g. more frequent beach cleaning in response to urbanisation, could have far reaching implications for both zones. Declaration relating to disposition of project thesis/dissertation I hereby grant to the University of New South Wales or its agents the right to archive and to make available my thesis or dissertation in whole or in part in the University libraries in all forms of media, now or here after known, subject to the provisions of the Copyright Act 1968. I retain all property rights, such as patent rights. I also retain the right to use in future works (such as articles or books) all or part of this thesis or dissertation. I also authorise University Microfilms to use the 350 word abstract of my thesis in Dissertation Abstracts International (this is applicable to doctoral theses only). Signature . Witness Signature . Date The University recognises that there may be exceptional circumstances requiring restrictions on copying or conditions on use. Requests for restriction for a period of up to 2 years must be made in writing. Requests for a longer period of restriction may be considered in exceptional circumstances and require the approval of the Dean of Graduate Research. FOR OFFICE USE ONLY Date of completion of requirements for Award: THIS SHEET IS TO BE GLUED TO THE INSIDE FRONT COVER OF THE THESIS