The seas have less oxygen now than they used to. Why, and what does this mean?

News: International Union for Conservation of Nature (IUCN) has released a report titled “Ocean deoxygenation: Everyone’s problem”. It reports the scale and nature of the changes being driven by ocean deoxygenation


Ocean Deoxygenation: It is defined as the reduction in oxygen content of the ocean due to anthropogenic effects.

Key takeaways from the report:

  • The levels of oxygen in the oceans fell by around 2% from 1960 to 2010.
  • The deoxygenation of the oceans occurred due to climate change and other human activities such as the nutrient runoff from farm fertilizers into waterways (nutrient pollution).

Impact of Ocean deoxygenation:

  • Reduction in the habitat available for pelagic, mesopelagic, and benthic organisms.
  • Reduction in the abundance of fish population
  • Expansion of the volume of anoxic zones (Waters with totally depleted oxygen levels) since 1960
  • Alteration in the balance of marine life by favouring low-oxygen tolerant species (e.g. microbes, jellyfish and some squid)

Measures to be taken:

  • Nutrient management: Reducing nutrient and carbon loads to coastal waters
  • Reducing the threat of global warming: Reduction in global greenhouse gas emissions through commitments  in four areas- policy, technology, finance and patterns of consumption
  • Adaptation in the face of oxygen decline: This should be done through ecosystem-based management of fisheries, spatial planning enhance ecosystem resilience, actions that reduce local stress on ecosystems etc.

Additional Information:


  •  It is an international organization working in the field of nature conservation and sustainable use of natural resources. It was established in 1948 and is headquartered in Gland, Switzerland.
  • IUCN has an observer and consultative status at the United Nations.
  • It is best known for compiling and publishing the IUCN Red List, which assesses the conservation status of species worldwide.