SUMMARY FOR POLICY MAKERS The Ocean is Losing its Breath Declining Oxygen in the World’s Ocean and United Nations Intergovernmental Educational, Scientific and Oceanographic Coastal Waters Cultural Organization Commission Published in 2018 by the Intergovernmental Oceanographic Commission of UNESCO (IOC-UNESCO) 7, place de Fontenoy, 75352 Paris 07 SP, France © IOC-UNESCO, 2018 Attribution-ShareAlike 3.0 IGO (CC-BY-SA 3.0 IGO) license (http://creativecommons.org/licenses/by-sa/3.0/igo/). By using the content of this publication, the users accept to be bound by the terms of use of the UNESCO Open Access Repository (http://www.unesco.org/open-access/terms-use-ccbysa-en). The present license applies exclusively to the textual content of the publication. For the use of any material not clearly identified as belonging to UNESCO, prior permission shall be requested from: [email protected] or UNESCO Publishing, 7, place de Fontenoy, 75352 Paris 07 SP France. Original title: The Ocean is Losing its Breath: Declining Oxygen in the World’s Ocean and Coastal Waters – Summary for Policy Makers. More Information on the Intergovernmental Oceanographic Commission of UNESCO (IOC-UNESCO) at http://ioc.unesco.org. The complete report should be cited as follows: Global Ocean Oxygen Network, Breitburg, D., M. Gregoire, K. Isensee (eds.) 2018. The ocean is losing its breath: Declining oxygen in the world’s ocean and coastal waters. IOC-UNESCO, IOC Technical Series, No. 137 40pp. (IOC/2018/ TS/137) The designations employed and the presentation of the material in this publication do not imply the expression of any opinion whatsoever on the part of the Secretariat of UNESCO and IOC concerning the legal status of any country or territory, or its authorities, or concerning the delimitation of the frontiers of any country or territory. The authors are responsible for the choice and presentation of the facts contained in the publication and for the opinion expressed therein, which are not necessarily those of UNESCO and do not commit the Organization. Graphic Design: UNESCO Cover design and typeset: Ana Carrasco-Martin Illustrations: Figures 3 and 5, Ana Carrasco-Martin Photos: © Andrey Kuzmin/Shutterstock.com, aquapix/Shutterstock. com, Milos Prelevic/Unsplash.com, NoPainNoGain/Shutterstock.com, Damsea/Shutterstock.com, Kaohanui/Shutterstock.com, Rich Carey/ Shutterstock.com, Hieu Vu Minh/Unsplash.com, Diego Fente Stamato / Shutterstock.com, Talia Cohen/Unsplash.com, Yanguang Ian/Unsplash. com, Digna Rueda Printed in UNESCO printshop, Paris, France (IOC/2018/TS/137 rev) (CLD 1863.18) The Ocean is Losing its Breath Declining Oxygen in the World’s Ocean and Coastal Waters Publication Team Prepared by the IOC expert working group: Global Ocean Oxygen NEtwork (GO2NE) Co-Chairs Denise Breitburg (Smithsonian Environmental Research Center, USA) Marilaure Grégoire (University of Liège, Belgium) Authors Kirsten Isensee (IOC-UNESCO, France) Francisco Chavez (MBARI, USA) Daniel Conley (Lund University, Sweden) Véronique Garçon (CNRS – Laboratoire d’Etudes en Géophysique et Océanographie Spatiales, France) Denis Gilbert (Fisheries and Oceans Canada, Canada) Dimitri Gutierrez (Instituto del Mar del Perú) Gil Jacinto (University of the Philippines Diliman) Lisa Levin (Scripps Institution of Oceanography, USA) Karin Limburg (SUNY College of Environmental Science and Forestry, USA) Ivonne Montes (Instituto Geofísico del Perú) Wajih Naqvi (National Institute of Oceanography, India) Andreas Oschlies (GEOMAR, Germany) Grant Pitcher (Department of Agriculture, Fisheries and Forestry, South Africa) Nancy Rabalais (Louisiana State University, Louisiana Universities Marine Consortium, USA) Mike Roman (University of Maryland, Center for Environmental Science, USA) Kenny Rose (University of Maryland, Center for Environmental Science, USA) Brad Seibel (University of South Florida, USA) Maciej Telszewski (International Ocean Carbon Coordination Project, Poland) Moriaki Yasuhara (The University of Hong Kong, China) Jing Zhang (East China Normal University, China) Table of contents Table of 5 DEOXYGENATION DISRUPTS THE BIOLOGICAL AND ECOLOGICAL FUNCTIONING OF MARINE contents ECOSYSTEMS 20 5.1 Impact of deoxygenation Publication team on food security 22 List of figures/boxes 5.2 Habitat compression 22 5.3 Aquaculture 22 1 6 DECLINING OXYGEN IN THE WORLD’S OCEANS: 15 THINGS TO KNOW 6 UNDERSTANDING DEOXYGENATION AS ONE OF THE MANY HUMAN IMPACTS ON OUR OCEAN AND COASTAL WATERS 24 2 THE PROBLEM OF DECLINING OXYGEN 7 IN THE OCEAN 8 OBSERVING OXYGEN DECLINE AND ITS EFFECTS 28 3 HUMAN ACTIVITIES ARE CAUSING OXYGEN 8 DECLINES IN THE OPEN OCEAN AND COASTAL WATERS 12 WHAT CAN BE DONE TO REDUCE DEOXYGENATION AND PROTECT 3.1 Excess nutrients 13 ECOSYSTEMS SERVICES EXPOSED 3.2 Climate change 16 TO LOW OXYGEN 32 4 9 WHY IS DEOXYGENATION A PROBLEM? 18 LITERATURE 34 4.1. Climate regulation and nutrient cycling 19 4.2 N2O greehouse gas production 19 4.3 Phosphorus release 19 4.4 Hydrogen sulphide 19 4.5 Micronutrient cycling 19 4 IOC THE OCEAN IS LOSING ITS BREATH SUMMARY FOR POLICY MAKERS 2018 List of figures/ boxes Figure 16: Upwelling along the coast of Namibia List of figures Figure 17: Vertical expansion of OMZs in the tropical north-east Atlantic Figure 1: OMZs and areas with coastal hypoxia Figure 18: A fish kill due to low oxygen concentrations in the world’s ocean in Bolinao, Philippines Figure 2: Deoxygenation in the ocean – causes and Figure 19: Global warming, acidification and consequences deoxygenation are linked Figure 3: Dissolved oxygen concentrations at 300 m depth Figure 20: Oxygen requirements of fish increase with in the open ocean increasing temperatures Figure 4: Coastal upwelling Figure 21: Low dissolved oxygen and acidification (low pH, high pCO ) occur together Figure 5: Impacts of excess nutrients (eutrophication) on 2 ocean oxygen Figure 22: Photo illustrating the deployment of an Argo Float in the Indian Ocean Figure 6: The number of water bodies in which hypoxia associated with eutrophication has been Figure 23: Field monitoring, numerical modelling and reported has increased exponentially since the experiments 1960s Figure 24: Experiments in the Adriatic investigating Figure 7: Recovery of oxygen saturation in the upper the impact of low oxygen concentration in Thames River Estuary (UK) the seawater on the behaviour of bottom- dwelling animals Figure 8: The cumulative number of fish species recorded in the Thames between Kew and Gravesend Figure 25: Lamination of sediments from the Black from 1964 to 1980 Sea Figure 9: Sea floor area covered by water with <2 mg L-1 dissolved oxygen from 1900 to 2011 in the Baltic Sea List of boxes Figure 10: Estimated spatial extent of hypoxia <2 mg L−1 and anoxia during 2012 in the Baltic Sea Box 1: Definitions Figure 11: Change in dissolved oxygen per decade Box 2: Natural low oxygen systems: OMZs and since 1960 from surface waters to the ocean upwelling bottom Box 3: Management actions Figure 12: Projected change in dissolved oxygen concentrations between the 1990s and 2090s Box 4: Combined environmental cost of hypoxia and nitrogen loads Figure 13: Most coastal hypoxic zones occur in regions with a predicted end-of-century water Box 5: Ecosystem services temperature increase of >2°C Box 6: Measures to improve the understanding, Figure 14: In a warming world, coastal waters in many predicting and minimizing impacts of oxygen areas are expected to experience more severe decline in the ocean and prolonged hypoxia than at present under Box 7: Using paleo-records to understand long-term the same nutrient loads dynamics of dissolved oxygen in the ocean Figure 15: There is concern that expanding low oxygen areas may influence biogeochemical cycles in ways that further exacerbate deoxygenation and global warming IOC THE OCEAN IS LOSING ITS BREATH SUMMARY FOR POLICY MAKERS 2018 5 1 Declining oxygen in the world’s oceans: 15 things to know 6 IOC GLOBAL OCEAN SCIENCE REPORT 2017 DECLINING OXYGEN IN THE WORLD’S OCEANS: 15 THINGS TO KNOW 1. Oxygen is critical to the health of the ocean. It structures 11. Slowing and reversing deoxygenation will require reducing aquatic ecosystems and is a fundamental requirement for greenhouse gas and black carbon emissions globally marine life from the intertidal zone to the greatest depths and reducing nutrient discharges that reach coastal 1 of the ocean. waters. Concerted international efforts can reduce carbon 2. Oxygen is declining in the ocean. Since the 1960s, the area emissions. of low oxygen water in the open ocean has increased by 12. The decline in oxygen in the ocean is not happening in 4.5 million km2, and over 500 low oxygen sites have been isolation. At the same time, food webs are disturbed due to identified in estuaries and other coastal water bodies. overfishing and physical destruction of habitats, and waters are getting warmer, more acidic, and experience higher 3. Human activities are a major cause of oxygen decline in nutrient loads. Management of marine resources will be both the open ocean and coastal waters. Burning of fossil most effective if the cumulative effects of human activities fuels and discharges from agriculture and human waste, on marine ecosystems are considered. which result in climate change and increased nitrogen and phosphorus inputs, are the primary causes. 13. More accurate predictions of ocean deoxygenation, as well as improved understanding of its causes, consequences 4. Deoxygenation (a decline in oxygen) occurs when oxygen in and solutions, require expanding ocean oxygen observation, water is used up at a faster rate than it is replenished. Both long-term and multi-stressor experimental studies, and warming and nutrients increase microbial consumption of numerical modelling. oxygen. Warming also reduces the supply of oxygen to the open ocean and coastal waters by increasing stratification 14. Accurate oxygen measurements with appropriate temporal and decreasing the solubility of oxygen in water. resolution and adequate spatial coverage in the marine environment are needed to document the current status of 5.