'Slippery slope' World's oceans losing oxygen at alarming rate, says study

Some of the most productive biomes in the ocean that support a fifth of the world's 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. The report is based on data on ocean water quality collected since the late 1950s. Minna Epps from IUCN told the media that they had earlier known about the phenomenon of de-oxygenation but were not aware of linkages to climate change.

Species such as tuna, marlin, and sharks are especially sensitive to lower oxygen levels due to their large size and high energy demand.

"Deoxygenation will have an [effect] on biodiversity, on the biomass of commercially [valuable] species and on vulnerable, rare species". The largest peer - reviewed study to date on ocean oxygen loss has concluded that deoxygenation is already altering the balance of marine life at the expense of species that need more vital gas.

"With this report, the scale of damage climate change is wreaking upon the ocean comes into stark focus".

"As the warming of the ocean loses oxygen, the delicate balance of marine life is disorganized".

These areas are especially vulnerable to even tiny variations in oxygen levels.

"Uninteresting zones" within the sphere's oceans are increasing at a quick rate, fuelled by a wide lower in oxygen ranges.

"Impacts here will ultimately ripple out and affect hundreds of millions of people", the IUCN said.


Under a business-as-usual model, the ocean is expected to lose 3 to 4 percent of its global oxygen inventory by 2100. In the tropics, more loss is expected in the top 1,000 metres of the water column, which is the richest in biodiversity.

This year, the group issued a historical assessment of the world's natural habitats, concluding that human activity threatened the extinction of up to one million species.

Ocean life is already struggling with warmer temperatures, unbridled overfishing and plastic pollution.

The World Meteorological Organization said this week that due to the growth of man-made emissions, the ocean is now 26 percent more acidic than before the Industrial Revolution.

The report pinpoints nutrient pollution and climate change as the major culprits in the depletion, which threatens several species of tuna, marlins and sharks - larger species that have greater oxygen needs. "This is perhaps the ultimate wake-up call from the uncontrolled experiment humanity is unleashing on the world's ocean as carbon emissions continue to increase", said Dan Laffoley, Senior Advisor Marine Science and Conservation in IUCN's Global Marine and Polar Programme and a co-editor of the report.

World leaders will gather in Marseille in June for the IUCN's World Conservation Congress.

Any changes to the ocean's oxygen concentration run the risk of collapsing food chains and causing widespread disruption throughout the marine ecosystem.

Policy makers are now negotiating at the COP25 climate summit in Madrid to ratify a comprehensive settlement for the 2015 Paris agreement.

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