Oxygen Loss in Oceans, Marine Life, and People


Majid Ali, M.D.

Course on Molecular Biology of Oxygen 

Oxygen is essential to most life in the ocean. An analysis shows that oxygen levels have declined by 2% in the global ocean over the past five decades, probably causing habitat loss for many fish and invertebrate species.

Ocean Oxygen Loss

Oxygen is the primary nutrient for oxyphilic acquatic life as it is for us humans. This is important to consider as we consider our the continung loss of oxygen in the planet’s oceans. A 2017 analysis reveals that oxygen levels of the globalocean (all oceans considered together) has declined over the past five decadesThe full impact of this loss has not been fully acknowledged. Below is text from a an article in the journal Nature of 16 February 2017.

Ocean models predict a decline in the dissolved oxygen inventory of the global ocean of one to seven per cent by the year 2100, caused by a combination of a warming-induced decline in oxygen solubility and reduced ventilation of the deep ocean1, 2. It is thought that such a decline in the oceanic oxygen content could affect ocean nutrient cycles and the marine habitat, with potentially detrimental consequences for fisheries and coastal economies3, 4, 5, 6.
Regional observational data indicate a continuous decrease in oceanic dissolved oxygen concentrations in most regions of the global ocean1, 7, 8, 9, 10, with an increase reported in a few limited areas, varying by study1, 10. Prior work attempting to resolve variations in dissolved oxygen concentrations at the global scale reported a global oxygen loss of 550 ± 130 teramoles (1012 mol) per decade between 100 and 1,000 metres depth based on a comparison of data from the 1970s and 1990s10. Here we provide a quantitative assessment of the entire ocean oxygen inventory by analysing dissolved oxygen and supporting data for the complete oceanic water column over the past 50 years.
We find that the global oceanic oxygen content of 227.4 ± 1.1 petamoles (1015 mol) has decreased by more than two per cent (4.8 ± 2.1 petamoles) since 1960, with large variations in oxygen loss in different ocean basins and at different depths. We suggest that changes in the upper water column are mostly due to a warming-induced decrease in solubility and biological consumption. Changes in the deeper ocean may have their origin in basin-scale multi-decadal variability, oceanic overturning slow-down and a potential increase in biological consumption11, 12.

 Schmidto S, Stramma L, Visbeck. Decline in global oceanic oxygen content during the past five decades. Nature. 2017;542:335-339.

Environmental science: Oceans lose oxygen. Nature 2017;542:335, & 542:30303-303.16 February 2017.

 More in Dr. Ali’s Course on Molecular Biology of Oxygen

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