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The Responses of Amphibolis Griffithii to Reduced Light Availability Kathryn

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The Responses of Amphibolis Griffithii to Reduced Light Availability Kathryn The responses of Amphibolis griffithii to reduced light availability A report on the outcomes of the SRFME Collaborative Research Project: Ecophysiology of benthic primary producers Final Report to SRFME / WAMSI and Geraldton Port Authority Kathryn McMahon and Paul Lavery Centre for Marine Ecosystems Research Edith Cowan University Report No. 2008-01 This report has been prepared to summarise the findings and management implications of the SRFME Collaborative Research Project: Ecophysiology of benthic primary producers. No portion of this material may be reproduced or communicated without the permission of ECU, unless the reproduction or communication is authorised by law. ECU 2008. The responses of Amphibolis griffithii to reduced light availability Final Report on the SRFME Collaborative Research Project: Ecophysiology of benthic primary producers. Kathryn McMahon and Paul Lavery Centre for Marine Ecosystems Research Edith Cowan University 100 Joondalup Dr, Joondalup, WA Australia Cite as: McMahon, K. and Lavery, P.S. (2007). The responses of Amphibolis griffithii to reduced light availability. Final Report on the Strategic Research Fund for the Marine Environment (SRFME) Collaborative Research Project: Ecophysiology of benthic primary producers. 148 p. Centre for Marine Ecosystems Research, Edith Cowan University, Joondalup, Western Australia. iii iv ii. Table of Contents i. Preface................................................................................................................................................................... ii. Table of Contents .............................................................................................................................................. v iii. List of Figures.................................................................................................................................................vii iv. List of Tables ...................................................................................................................................................xi v. Acknowledgements ........................................................................................................................................xiii 1. Executive Summary........................................................................................................................................... 1 2. Rationale and Background ................................................................................................................................ 9 3. Research Framework .......................................................................................................................................14 4. Report Format ..................................................................................................................................................15 5. Methodology ....................................................................................................................................................17 5.1 Experimental design...................................................................................................................................17 5.2 Site location ................................................................................................................................................19 5.3 Environmental parameters measured........................................................................................................20 5.4 Biological parameters measured ...............................................................................................................20 5.5 Data quality ................................................................................................................................................21 5.6 Statistical analysis ......................................................................................................................................22 6. Environmental Responses ...............................................................................................................................25 6.1 Light (PPFD) ..............................................................................................................................................25 6.2 Water temperature......................................................................................................................................25 7. Seagrass Response to PPFD Reduction Treatments......................................................................................27 7.1 Biomass.......................................................................................................................................................27 7.2 Density ........................................................................................................................................................32 7.3 Morphology ................................................................................................................................................36 7.4 Growth ........................................................................................................................................................42 7.5 Sexual reproduction ...................................................................................................................................45 7.6 Physiology ..................................................................................................................................................46 7.7 Impact – response pathway .......................................................................................................................52 8. Canopy Response to 3-months PPFD Reduction Post-summer ...................................................................57 8.1 Biomass and density ..................................................................................................................................58 8.2 Morphology ................................................................................................................................................59 8.3 Growth ........................................................................................................................................................60 8.4 Physiology ..................................................................................................................................................61 9. Recovery From 3-month PPFD Reduction Treatments ................................................................................69 9.1 Biomass.......................................................................................................................................................69 9.2 Density ........................................................................................................................................................73 v 9.3 Morphology ................................................................................................................................................74 9.4 Growth ........................................................................................................................................................78 9.5 Sexual reproduction ...................................................................................................................................80 9.6 Physiology ..................................................................................................................................................81 9.7 Recovery - response pathway of A. griffithii after 3-months of PPFD reduction .................................88 10. Recovery From 6-month PPFD Reduction Treatments ..............................................................................91 10.1 Biomass and density ................................................................................................................................91 11. Recovery From 9-month PPFD Reduction Treatments ..............................................................................97 11.1 Biomass and density ................................................................................................................................97 12. Sub-lethal Indicators....................................................................................................................................102 12.1 Sub-lethal indicators of PPFD reduction ..............................................................................................102 12.2 Sub-lethal indicators of recovery from PPFD reduction .....................................................................104 12.3 Summary statistics of possible sub-lethal indicators ...........................................................................106 12.4 Potential indicators of sub-lethal reduction in light availability .........................................................109 13. Management Application of the Research Results....................................................................................115 13.1 Environmental modeling .......................................................................................................................116 13.2 Impact prediction ...................................................................................................................................125 13.3 Impact management...............................................................................................................................130
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