New research has uncovered a significant drop in oxygen levels across Earth's lakes, with some losing oxygen up to nine times faster than oceans. Between 1980 and 2017, global lake oxygen levels declined by 5.5 per cent in surface waters and 18.6 per cent in deep waters, according to a study published in Science Advances.

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Heatwaves and rising temperatures are major culprits

Researchers from the Chinese Academy of Sciences (CAS), led by geographer Yibo Zhang, analysed satellite imagery and climate data to understand the causes behind these losses. 

Their study found that from 2003 to 2023, 85 per cent of the 15,535 lakes examined experienced an increase in heatwave days per year. These heatwaves contributed to 7.7 per cent of the oxygen depletion by reducing water’s ability to retain oxygen.

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However, the most significant factor remains rising global temperatures, which account for up to 55 per cent of the oxygen loss. If this warming trend continues, lakes worldwide could experience an additional 9 per cent decline in oxygen by the end of the century.

Algal blooms worsening the crisis

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Beyond temperature increases, the researchers attributed 10 per cent of the oxygen decline to more frequent and severe algal blooms. These blooms, fueled by excess nutrients from fertilizer runoff and livestock waste, consume large amounts of oxygen, further depleting lake ecosystems.

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Consequences for wildlife and human communities

Oxygen depletion is creating ‘dead zones’ in lakes, making them uninhabitable for aquatic life. Mass die-offs of fish and other species have already been observed worldwide, including eels in New Zealand, Murray cod in Australia, and fish and mussels in Poland and Germany.

Lakes are also facing increased evaporation due to a warming atmosphere, accelerating shifts between drought and flooding. These disruptions threaten ecosystems and local economies, with severe implications for food security. The destruction of Earth’s fourth-largest lake serves as a stark warning of the consequences.
Potential Solutions.

According to CAS ecologist Shi Kun, planting submerged vegetation and constructing wetlands could also play a role in restoring lake ecosystems.