Deoxygenation –
Open Ocean and Coastal Waters

Oxygen is critical to the health of the planet. It affects the cycles of carbon, nitrogen and other key elements, and is a fundamental requirement for marine life from the seashore to the greatest depths of the ocean. Nevertheless, deoxygenation is worsening in the coastal and open ocean. This is mainly the result of human activities that are increasing global temperatures (CO2-induced warming) and increasing loads of nutrients from agriculture, sewage, and industrial waste, including pollution from power generation from fossil fuels and biomass.

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There are 10 main ocean oxygen concerns:

  1. Increasing temperatures will reduce the capacity of the ocean to hold oxygen in the future;
  2. Oxygen deficiency is predicted to worsen in estuaries, coastal areas and oxygen minimum zones in the open ocean;
  3. The ocean’s capacity to produce oxygen will be reduced in the future.
  4. Habitat loss is expected to worsen, leading to vertical and horizontal migration of species;
  5. Oxygen deficiency will alter biogeochemical cycles and food webs;
  6. Lower oxygen concentrations are projected to result in a decrease in reproductive capacity and biodiversity loss;
  7. There are important local decreases of commercially important species and aquaculture production;
  8. Harmful Algal Blooms might benefit from nutrients released in bottom waters due to hypoxia (e.g. in the Baltic Sea);
  9. Reduced ocean oxygen concentrations will lead to an increase in greenhouse gas emissions, thereby initiating feedbacks on climate change;
  10. Future scenarios for oxygen depend on a combination of drivers related to global environmental change and land-use, including warming, growing human population, and extensive coastal agricultural practices, which, in turn, act together in affecting marine ecosystems – thus, a multi-stressor approach is important.

Global Ocean Oxygen Network

”Reverse

Through the participation of high level scientists from across the world, the IOC expert group, the Global Ocean Oxygen Network GO2NE, established in 2016, is committed to providing a global and multidisciplinary view of deoxygenation, with a focus on understanding its multiple aspects and impacts. The Network offers scientific advice to policy makers to counter this concerning trend and to preserve marine resources in the presence of deoxygenation. Currently, the members of the core working group represent 21 institutions in 11 countries.

The Network’s scientific work, outreach, and capacity building efforts include facilitating communication with other established networks and working groups (e.g. IOCCP, GOOS, IGMETS, GOA-ON, GlobalHAB, WESTPAC O2NE), improving observations systems, identifying and filling knowledge gaps, as well as developing related capacity development activities. GO2NE is moreover preparing a summary on deoxygenation for policy makers.

In collaboration with SFB754, it recently initiated the news site ocean-oxygen.org to provide information on deoxygenation to scientists, stakeholders and the interested public.

Group picture of the GO2NE working group (2017, Monterey, USA).

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