COOK ISLANDS MARAE MOANA Marine Outlook Report 2020 Prepared by Teina Rongo, Ph.D. Marine Biology Teariki-Taoiau Rongo Jackalyn Rongo COOK ISLANDS MARAE MOANA Marine Outlook Report 2020 1 Disclaimer The authors have made reasonable efforts to ensure that the contents of this report are factually correct – borrowing the format of the well- established Great Barrier Reef Outlook Report, which Section 34 of the Cook Islands Marae Moana Act 2017 alludes to. However, the authors do not make any representation or give any warranty regarding the accuracy, completeness, currency or suitability for any particular purpose of the source material contained in this report. Readers should consult the source material referred to and, where necessary, seek appropriate advice about the suitability of the publication for their needs. The authors shall not be liable for any loss, damage, cost or expense that may be occasioned directly or indirectly through the use of or reliance on the contents of this publication. How to cite this report Rongo, T.*, Rongo, T.T., Rongo, J. 2020. Cook Islands Marae Moana: Marine Outlook Report 2020. Government of the Cook Islands. 123 p. *Corresponding author: PO Box 881, Avarua, Rarotonga, Cook Islands; [email protected]. 2 TABLE OF CONTENTS LETTER OF TRANSMITTAL.................................................................................................................................................................... 7 ACKNOWLEDGEMENTS......................................................................................................................................................................... 8 EXECUTIVE SUMMARY.......................................................................................................................................................................... 9 1. ABOUT THIS REPORT........................................................................................................................................................................10 1.1 Background .................................................................................................................................................................... 10 1.2 Scope ............................................................................................................................................................................. 11 1.3 Methodology of assessment............................................................................................................................................ 13 1.3.1 Assessing values………….......................................................................................................................... 13 1.3.2 Assessing trends……….............................................................................................................................. 14 1.3.3 Management of threats and risks................................................................................................................ 14 1.3.4 Evidence used…………………………..........................................................................................................14 2. ECOSYSTEM HEALTH........................................................................................................................................................................ 15 2.1 Background ...................................................................................................................................................................... 15 2.2 Current condition and trends of physical processes .........................................................................................................16 2.2.1 Currents ........................................................................................................................................................16 2.2.2 Cyclones and wind ............................................................................................... ……………………………17 2.2.3 Freshwater inflow ................................................................................................................... ………………20 2.2.4 Sedimentation ...............................................................................................................................................22 2.2.5 Sea level .......................................................................................................................................................25 2.2.6 Sea temperature .......................................................................................................................................... 26 2.2.7 Light ............................................................................................................................................................. 27 2.3 Current condition and trends of chemical processes ....................................................................................................... 28 2.3.1 Nutrient cycling............................................................................................................................................. 28 2.3.2 Ocean pH..................................................................................................................................................... 29 2.3.3 Ocean salinity............................................................................................................................................... 30 2.4 Current condition and trends of ecological processes...................................................................................................... 31 2.4.1 Microbial processes ..................................................................................................................................... 31 2.4.2 Particle feeding............................................................................................................................................. 32 2.4.3 Primary production........................................................................................................................................ 32 2.4.4 Herbivory...................................................................................................................................................... 34 2.4.5 Predation...................................................................................................................................................... 35 2.4.6 Recruitment ..................................................................................................................................................36 2.4.7 Connectivity................................................................................................................................................ 37 2.5 Current condition and trends in terrestrial habitats that support the islands of Marae Moana ......................................... 37 2.5.1 Saltmarshes ................................................................................................................................................ 37 2.5.2 Wetlands...................................................................................................................................................... 38 2.5.3 Riparian zone………………………………………………………………………………………………………… 38 2.6 Current condition and trends of outbreaks of disease, pests and introduced species………………..................................39 2.6.1 Outbreaks of disease.....................................................................................................................................39 2.6.2 Outbreaks of Crown-Of-Thorns starfish........................................................................................................ 40 2.6.3 Introduced species ...................................................................................................................................... 41 2.6.4 Other outbreaks........................................................................................................................................... 41 2.7 Assessment summary – Ecosystem health...................................................................................................................... 42 2.7.1 Physical processes....................................................................................................................................... 42 2.7.2 Chemical processes .................................................................................................................................... 42 2.7.3 Ecological processes .................................................................................................................................. 42 2.7.4 Terrestrial habitats that support the islands of Marae Moana...................................................................... 42 2.7.5 Outbreaks of disease and introduced species............................................................................................. 43 2.7.6 Overall summary of ecosystem health ......................................................................................................... 43 3. BIODIVERSITY……………………………………………………………….............................................................................................. 44 3.1 Background ...................................................................................................................................................................... 44 3.2 Legacies and shifted baselines .......................................................................................................................................