Ocean Deoxygenation – Another Global Challenge

By Sylvia Earle1,2, Dawn J. Wright3,4, Samantha Joye5, Dan Laffoley6, John Baxter6, Carl Safina8, and Patty Elkus2

1 National Geographic Society Explorer-in-Residence, Washington, DC 20036, USA.

2 Mission Blue, Napa, CA 94581, USA.

3 Environmental Systems Research Institute, Redlands, CA 92373, USA.

4 College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, USA.

5 Department of Marine Sciences, University of Georgia, Athens, GA 30602, USA.

6 International Union for Conservation of Nature World Commission on Protected Areas, Gland, SWITZERLAND.

7 School of Marine and Atmospheric Sciences, Stony Brook University, Setauket, NY 11733, USA.

The ocean is facing unprecedented pressures that are causing massive ecosystem and nutrient cycle disruption the result of industrial-scale depletion of ocean wildlife and destabilization of steady-state ecosystems. This occurs not only on the seafloor by trawling, dredging, drilling, and mining (1) but also in the water column with nets, long lines, fish aggregating devices and other techniques; methods introduced in recent decades to extract with unprecedented speed and scale from ecosystems hundreds of millions of years in the making. Indeed, the carbon cycle/climate impacts of overfishing of the ocean biomass are tremendous (2), and restoring ocean life could have a huge impact, not just on ocean health but on CO2 accumulation in the atmosphere (3). Since more than half of the oxygen produced on Earth is derived from phytoplankton, decline of oxygen in the ocean concerns life on land as well.


Example of a visualization representing a new three-dimensional classification for the ocean known as ecological marine units (EMUs), www.esri.com/ecological-marine-units. The region shown is south of Tasmania, Australia [though we at Esri can re-create for any part of the world including the Baltic Sea or Indian Ocean highlighted in the Breitburg et al. paper]. Although the EMUs are mapped as a continuous surface, representing them in 3D is facilitated using columnar stacks (in this case dissolved oxygen), allowing visualization of EMUs beneath the ocean surface at evenly-spaced locations. In the coastal zone, EMUs are single or few, whereas offshore there are more and deeper EMUs. Visualization by Sean Breyer and Keith Van Graafeiland, both of Esri.

In their review “Declining oxygen in the global ocean and coastal waters” (05 January, p. eaam7240), D. Breitburg et al. summarize the evidence for the decline of oxygen in open ocean and coastal waters over the past half-century, yet another consequence of the human activities that have increased emissions of greenhouse gas, as well as nutrient discharges to coastal waters. While further studies are needed to help understand the long-term, global- and regional-scale changes in oxygen and their effect on ocean species and ecosystems, we suggest that new insights about the role and speed of microbial engagement, including how deoxygenation is altering microbial pathways and rates of processes within the water column and the deep ocean represent additional critically important data gaps. Breitburg et al. point out that oxygen is dropping faster than can be accounted for by physics, which suggests that respiration must be increasing. However, a good portion of this may in fact be microbial. And the extent to which the system is out of balance is becoming clear, exposed now to the point of crisp detection and quantification (4, 5). The pace of this change is alarming, as well as how widespread the impacts are (6). We cannot afford to wait before action is taken.


Interactive Atlas of Marine Protection. Marine Conservation Institute (2018), MPAtlas [Online]. Seattle, WA. Available at: www.mpatlas.org/map/mpas. [Accessed 15-Jan-2018].

In addition to an integrated framework that combines modeling, observations, and experiments among scientists, local governments, intergovernmental bodies, and industrial sectors, Breitburg et al. call for a “raised awareness” of the phenomenon of deoxygenation. We contend that such awareness must extend to all facets of society, beyond the pages of scientific journals, and most readily by way of intuitive, interactive, dynamic web maps and visualizations, such as the new Ecological Marine Units digital ocean project (7, 8), that drive the point home to a variety of audiences. These will be key to generating the societal and political will toward the effective management that will ultimately reverse deoxygenation, and its serious consequences for ocean life, ecosystems and habitats. As a companion to Explaining Ocean Warming: Causes, Scale, Effects and Consequences (3), the IUCN, in collaboration with world experts, is coordinating the production of Ocean Deoxygenation – Everyone’s Problem: Causes, Impacts, Consequences and Solutions (9), that will further summarize the challenges and implications we face. We must connect important discoveries about the nature of the world with public perception and current policies that shape the habitability of Earth. The global trend by nations of securing large areas of the ocean within national Exclusive Economic Zones (EEZs) or on the high seas as “blue parks” or safe havens for ocean life is also cause for hope, because protecting nature protects our existence.


There is accelerating momentum and opportunity for designating very large marine protected areas. Research suggests large MPAs are much more cost-effective to implement and manage compared to smaller MPAs and in general larger areas will provide better protection from activities that occur outside the MPA. Marine Conservation Institute (2018), MPAtlas [Online]. Seattle, WA. Available at: www.mpatlas.org/protection-dashboard/very-large-mpas  [Accessed 15-Jan-2018].


  1. A. Boetius, M. Haeckel, Mind the seafloor. Science 359, 34 (2018). [link]
  2. C. B. Woodson, J. R. Schramski, S. B. Joye, A unifying theory for top-heavy ecosystem structure in the ocean. Nature Communications 9, 23 (2018). [link]
  3. D. Laffoley, J. M. Baxter, Eds., Explaining Ocean Warming: Causes, Scale, Effects, and Consequences, (International Union for Conservation of Nature and Natural Resources (IUCN), Gland, Switzerland), 456 pp., (2016). [link]
  4. Á. López-Urrutia, E. San Martin, R. P. Harris, X. Irigoien, Scaling the metabolic balance of the oceans. Proceedings of the National Academy of Sciences 103, 8739-8744 (2006). [link]
  5. L. Cheng et al., Improved estimates of ocean heat content from 1960 to 2015. Science Advances 3,(2017). [link]
  6. R. N. Glud et al., High rates of microbial carbon turnover in sediments in the deepest oceanic trench on Earth. Nature Geoscience 6, 284-288 (2013). [link]
  7. A. Witze, 3D ocean map tracks ecosystems in unprecedented detail. Nature 541, 10-11 (2017). [link]
  8. R. Sayre et al., A three-dimensional mapping of the ocean based on environmental data. Oceanography 30, 90-103 (2017). [link]
  9. D. Laffoley, J. M. Baxter, Eds., Ocean Deoxygenation – Everyone’s Problem: Causes, Impacts, Consequences and Solutions, (International Union for Conservation of Nature and Natural Resources (IUCN), Gland, Switzerland, in press 2018).