Impacts of ocean acidification on predator – prey interactions of molluscs John Matthew Wright A thesis submitted to the University of Sydney in fulfilment of the requirements for the degree of Doctor of Philosophy School of Life and Environmental Sciences, University of Sydney February 2017 1 Table of contents Acknowledgements ............................................................................................................ 5 List of achievements in the candidature .............................................................................. 7 Attribution of authorship ................................................................................................... 9 Statement of authentication ............................................................................................. 11 Abstract ........................................................................................................................... 12 Chapter one - General introduction .................................................................................. 16 1.1 Climate change ................................................................................................................ 16 1.2 Evidence for climate change ............................................................................................ 17 1.3 Changing ocean chemistry ............................................................................................... 17 1.4 Ocean acidification .......................................................................................................... 19 1.5 Response of marine molluscs .......................................................................................... 21 1.6 Alterations to predator-prey interactions ....................................................................... 22 Physiology and metabolic function ........................................................................................ 28 Calcification and morphology ................................................................................................ 29 Behaviour ............................................................................................................................... 32 1.7 Aims and hypotheses of this thesis ................................................................................. 33 Chapter two - Predation by the endemic whelk Tenguella marginalba on the invasive Pacific oyster Crassostrea gigas ................................................................................................... 36 2.1 Abstract ........................................................................................................................... 36 2.2 Introduction ..................................................................................................................... 37 2.3 Materials and methods ................................................................................................... 39 Initial observations ................................................................................................................ 40 Predation of C. gigas .............................................................................................................. 41 Impacts of emersion and illumination on C. gigas predation ................................................ 42 Statistical analyses ................................................................................................................ 43 2.4 Results ............................................................................................................................. 44 Observations of predation ..................................................................................................... 44 Predation of C. gigas .............................................................................................................. 45 Impacts of emersion and illumination on C. gigas predation ................................................ 45 2.5 Discussion ........................................................................................................................ 46 2 Chapter three - Ocean acidification alters the predator-prey interactions between the oysters Saccostrea glomerata and Crassostrea gigas and the whelk Tenguella marginalba 49 3.1 Abstract ........................................................................................................................... 49 3.2 Introduction ..................................................................................................................... 50 3.3 Materials and Methods ................................................................................................... 52 Collection and feeding of Saccostrea glomerata, Crassostrea gigas and Tenguella marginalba ..................................................................................................................... 52 Experiment 1: Shell morphology and physiology of S. glomerata and C. gigas .................. 594 Experiment 2: Physiological responses of S. glomerata and C. gigas to chemical cues from T. marginalba ..................................................................................................................... 60 Statistical analyses ................................................................................................................ 62 3.4 Results ............................................................................................................................. 64 Shell morphology and physiology of S. glomerata ................................................................ 64 Shell morphology and physiology of C. gigas ........................................................................ 65 Shell morphology and physiology of T. marginalba .............................................................. 69 Predation of S. glomerata by T. marginalba ......................................................................... 69 Predation of C. gigas by T. marginalba ................................................................................. 71 Dry flesh mass consumed by T. marginalba .......................................................................... 72 Physiological responses of S. glomerata and C. gigas to chemical cues from T. marginalba 73 3.5 Discussion ........................................................................................................................ 74 Chapter four - Populations of Pacific oysters Crassostrea gigas respond variably to elevated pCO2 and predation by Tenguella marginalba ................................................................... 80 4.1 Abstract ........................................................................................................................... 80 4.2 Introduction ..................................................................................................................... 81 4.3 Method ............................................................................................................................ 83 Organism ............................................................................................................................... 83 Collection and feeding of Crassostrea gigas and Tenguella marginalba .............................. 83 Experimental set-up ............................................................................................................... 84 The effect of pCO2 on growth and strength of the shell ........................................................ 87 The effect of pCO2 on standard metabolic rate .................................................................... 89 The effect of pCO2 on predation ................................................ 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Statistical analyses ................................................................................................................ 89 4.4 Results ............................................................................................................................. 90 Response among family lines of C. gigas ............................................................................... 90 Whelk ..................................................................................................................................... 97 3 Effect of pCO2 on predation ................................................................................................... 97 4.5 Discussion ...................................................................................................................... 100 Effect of pCO2 on growth, strength and standard metabolic rate ....................................... 100 Effect of pCO2 on predation ................................................................................................. 102 Conclusion ........................................................................................................................... 104 Chapter five - Responses of diploid and triploid Pacific oysters Crassostrea gigas to elevated pCO2 ................................................................................................................ 106 5.1 Abstract ......................................................................................................................... 106 5.2 Introduction ................................................................................................................... 107 5.3 Methods .......................................................................................................................