Preventing water crises
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Preventing water crises

Dropping oxygen levels of the oceans to cause ecological crisis

It is a lesser known fact that climate change is also making the oxygen levels of the oceans drop. Over the last 50 years, the average oxygen content of the world’s oceans has dropped by almost 2%, which may have dramatic consequences.

Today, the area of oceanic zones with insufficient oxygen to sustain life are growing. Something similar occurred 420 million years ago, during the so-called Lau/Kozlowskii extinction event: 23% of marine life forms went extinct due to the reduced level of oxygen.

The Lau/Kozlowskii extinction event is a long-standing subject of dispute among scientists, as it was not associated with any specific occurrence such as a massive volcanic eruption or meteor impact. Researchers at Florida State University (FSU) believed it was particularly important to study that extinction because a similar global decline in biodiversity is taking place today, so the research may shed light on the potential outcomes of various present climate scenarios.

The researchers at FSU measured the quantity of thallium and sulphur isotopes and the concentration of manganese in sediment samples collected in Lithuania and Sweden, and used the data to establish a precise timeline of the decline in oceanic oxygen levels.

The research has established a clear link between mass extinction and the drop in oxygen levels. During the event, deep sea creatures died out first, then oxygen was depleted in shallower waters too, and the concentration of sulphurous compounds also grew to make the oceans even less habitable.

The link between the extinction 420 million years ago and the lack of oxygen in the water paints a bleak picture of the future: the recent, relatively fast 2% drop in the oxygen level of the oceans foreshadows an ecological crisis.

Lack of oxygen represents severe stress for living organisms, so we must not disregard this consequence of climate change Photo: Shutterstock
Further information: Florida State University

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