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IUCN report on Ocean deoxygenation

Posted on : 13 Jan 2020

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  • The primary causes of deoxygenation are:
  • Eutrophication (increased nutrient run-off from land and sewage pollution).
  • Nitrogen deposition from burning of fossil fuels.
  • Widespread impacts from ocean warming.
  • Ocean oxygen loss is closely related to ocean warming and acidification caused by anthropogenic carbon dioxide emissions and biogeochemical consequences related to anthropogenic fertilization of the ocean.
  • As the ocean warms, its water hold less oxygen and become more buoyant, resulting in reduced mixing of oxygen-rich water near the surface with the ocean depths, which naturally contain less oxygen.
  • Nutrient pollution causes oxygen loss in coastal waters. Fertiliser, sewage, animal and aquaculture waste cause excessive growth of algae, which in turn deplete oxygen as they decompose.
  • The loss of oxygen from world’s ocean is increasingly threatening fish species and disrupting ecosystems.
  • Deoxygenation is starting to alter the balance of marine life , favouring low-oxygen tolerant species (e.g. microbes, jellyfish and some squid) at the expense of low-oxygen sensitive ones (many marine species, including most fish).
  • Some of the ocean’s most productive biomes – which support one fifth of the world’s wild marine fish harvest – are formed by ocean currents carrying nutrient-rich but oxygen-poor water to coasts that line the eastern edges of the world’s ocean basins.
  • As naturally oxygen-poor systems, these areas are particularly vulnerable to even small changes in ocean oxygen.
  • Impacts here will ultimately ripple out and affect hundreds of millions of people.
  • Species groups such as tuna, marlin and sharks are particularly sensitive to low oxygen because of their large size and energy demands.
  • These species are starting to be driven into increasingly shallow surface layers of oxygen-rich water, making them more vulnerable to overfishing.
  • Very low ocean oxygen can also affect basic processes like the cycling of elements crucial for life on Earth, such as nitrogen and phosphorous.

Article Related Questions

  1. Recently, IUCN released a report on Ocean deoxygenation. Which of the following statements is correct regarding the process of ocean deoxygenation?
    1.Warm ocean waters hold less oxygen and become more buoyant.
    2.Nutrient pollution causes excessive growth of algae.
    3.Deoxygenation favours low-oxygen sensitive marine species.
    Choose the correct answer:

  2. 1.1 only

    2.1 and 2 only

    3.2 and 3 only

    4.1, 2 and 3

    Right Ans : 1 and 2 only

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