Oceans Are Losing Oxygen at Unprecedented Level: Study
Mon, April 19, 2021

Oceans Are Losing Oxygen at Unprecedented Level: Study

The ocean produce half of the oxygen people breathe. / Photo credit by mihtiander via 123rf



Everybody knows that trees and plants produce a part of the oxygen that all living organisms need. However, we often do not credit our oceans, which produce more than half of the oxygen we breathe. Previous studies show that most of this oxygen comes from phytoplankton, a tiny plant that lives near the water’s surface and drifts with the current. Phytoplankton also photosynthesizes like all plants.

Scientists believe that phytoplankton contributes between 50% to 85% of oxygen to our planet’s atmosphere. According to Ocean Portal, a part of the Smithsonian Institution’s Ocean Initiative that focuses on everything ocean, the ocean has been producing oxygen for billions of years, even before land plants produced oxygen for our planet. Oceans and seas produce more oxygen than plants and trees – the proportions are not even close. 



With oceans, all living organisms are able to thrive for millions of years. Without it, we might not have come to exist. Numerous studies have shown that greenhouse gases are depriving our oceans of oxygen. A recent study published by the World Meteorological Organization found that more than 90% of the energy trapped by greenhouse gases goes into the oceans. In 2018, experts reported new highs of ocean temperature in the top 700 meters and 2,000 meters of water. 

“This global problem, compared to the issue of plastics pollution, is typically ‘unseen’ but no less important, as it adds further to nutrient pollution from wastewater, agricultural and other industrial runoff that is carried to the marine environment by rivers,” Christopher Cox, programme management officer on marine pollution at UN Environment, said. 

Gabriel Grimsditch, programme management officer for marine ecosystems at UN environment, stated that humans are pushing the boundaries of our oceans. Humans have been polluting the world’s water, resulting in ocean warming, ocean acidification, and sea-level rise.

Oceans Are Losing Oxygen

Since the 1950s, our world’s oceans have lost around 2% of oxygen. It is expected to lose about 3% to 4% by the year 2100 if the current status of climate change doesn’t change. Recently, the International Union for Conservation of Nature (IUCN) reported that oxygen in the oceans is being lost at an unprecedented rate, threatening marine species. Climate change is making the lack of oxygen worse with now about 700 ocean sites suffering from low oxygen. This is higher than the 45 sites in the 1960s.

According to The Guardian, a British daily newspaper, the “dead zones” in oceans are proliferating. It has been reported that hundreds more areas have their oxygen being dangerously depleted due to the climate emergency and intensive farming. This issue adds to the existing problem of nutrient run-off of chemicals such as nitrogen and phosphorus from farms. The IUCN report revealed that the biggest marine species are vulnerable to depleted oxygen levels because they need much more to survive. This forces them to move towards the surface and shallow areas of the sea. Unfortunately, these are the areas where they are the most vulnerable.



Some ocean areas that have lower oxygen compared to others are also at risk of depleting oxygen levels. As a result, marine species that can more easily tolerate low oxygen levels like marine microbes, some squid, and jellyfish would flourish but at the expense of fish. This could deeply upset the balance of ecosystems. According to the BBC, a British public service broadcaster, marine life can be significantly affected even by small changes in the ocean. Lack of oxygen would particularly affect species like tuna, marlin, and some sharks.

"We have known about deoxygenation but we haven't known the linkages to climate change and this is really worrying. Not only has the decline of oxygen quadrupled in the past 50 years but even in the best-case emissions scenario, oxygen is still going to decline in the oceans,” Minna Epps from IUCN said. 

Ocean deoxygenation not only alters the balance of marine life but also influences the movement of gases between the ocean and the atmosphere. Deoxygenated deeper ocean waters would produce greenhouse gases such as methane, carbon dioxide, and nitrous oxide. These gases may reach the ocean surface and be released into the atmosphere, contributing to further warming.

What Can Be Done?


Ending overfishing is a quick action that will restore fish populations. / Photo credit by Jakub Gojda via 123rf


Reducing carbon dioxide emissions is the best solution to address ocean deoxygenation. People and industries must urgently cut carbon dioxide emissions and reduce ocean nutrient pollution. This would not only benefit the oceans but our entire planet. 

Also, experts state that protecting marine life could help oceans function better. They could soak up more carbon while also providing barriers against sea level rises and storm surges through coral reefs and mangrove swamps. Dr. Monica Verbeek, the executive director of the group Seas at Risk, stated that we could substantially slow down the rate of climate breakdown through a healthy ocean with abundant wildlife. 

“To date, the most profound impact on the marine environment has come from fishing. Ending overfishing is a quick, deliverable action that will restore fish populations, create more resilient ocean ecosystems, decrease CO2 pollution and increase carbon capture, and deliver more profitable fisheries and thriving coastal communities,” Verbeek said. 

Oceans losing oxygen is not only a threat to marine life but a threat to all living organisms on our planet. Governments should start acting on these issues before it’s too late.