Earth's water depleting oxygen rapidly: Poses significant threat

A recent study has highlighted a rapid decline in dissolved oxygen levels in the world’s water bodies, presenting a significant threat to Earth's life support systems. According to a team of U.S. scientists, this issue is primarily driven by climate change and greenhouse gas emissions, as reported by Science Alert. Warmer waters, which hold less oxygen, pose a critical problem for aquatic life that depends on dissolved oxygen for survival, akin to the essential role of atmospheric oxygen for humans and animals.


The reduction of dissolved oxygen (DO) in water bodies is rapidly depleting worldwide and is emerging as one of the greatest threats to Earth's life support systems. Just as atmospheric oxygen is crucial for terrestrial animals, dissolved oxygen is essential for maintaining healthy aquatic ecosystems, both freshwater and marine. This decline is particularly alarming given that billions of people depend on these habitats for food and income.

Proposal to expand planetary boundaries

As per reports, a team of scientists, led by freshwater ecologist Kevin Rose from Rensselaer Polytechnic Institute, is advocating for the inclusion of aquatic deoxygenation in the list of 'planetary boundaries.' This concept outlines nine critical thresholds, including climate change, ocean acidification, and biodiversity loss, within which humanity can sustainably develop. The addition of aquatic deoxygenation is suggested as a crucial factor affecting the integrity of Earth's ecological and social systems.

Causes of dissolved oxygen decline

The decrease in dissolved oxygen levels is attributed to several factors:

• Warmer waters

Higher temperatures reduce the amount of oxygen that water can hold. Increased greenhouse gas emissions are raising both air and water temperatures, leading to a decrease in oxygen retention.

• Biological activity:

Aquatic life can deplete oxygen faster than it can be replenished. Algal blooms and bacterial growth, stimulated by excess nutrients from fertilisers, sewage, and industrial waste, consume large amounts of oxygen. When oxygen levels drop significantly, microbes suffocate, leading to a cycle of eutrophication where the lack of oxygen further disrupts the ecosystem.

Impact of water column stratification

Increased density differences between water layers—due to faster warming of surface waters and reduced salinity from melting ice—impair the movement of oxygenated water to deeper layers. This disruption in vertical water movement affects the oxygenation of deeper aquatic environments, worsening the deoxygenation problem.

Consequences of Aquatic Oxygen Depletion

A team led by freshwater ecologist Kevin Rose from Rensselaer Polytechnic Institute has raised alarms about the oversight of crucial environmental limits on Earth. They argue that the observed deoxygenation of freshwater and marine ecosystems should be recognized as a significant planetary boundary process. This process is vital for maintaining the integrity of both ecological and social systems, influencing and responding to changes in other planetary boundary processes.


The team highlights that critical oxygen thresholds are being approached at rates similar to other planetary boundaries. The decrease in dissolved oxygen concentration is attributed to several factors. Warmer waters, which result from rising greenhouse gas emissions and increased temperatures, cannot hold as much dissolved oxygen. Additionally, algal blooms and bacterial growth driven by sewage, industrial waste, and fertilizers contribute to oxygen depletion by consuming this essential element.


In severe cases, the depletion of oxygen has led to the death of microbes due to suffocation.





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