Something of 'serious concern' is happening to a huge area of Earth's ocean with big consequences

Wales Online

28-05-2025

Something of 'serious concern' is happening to a huge area of Earth's ocean with big consequences
The changes could have a profound impact on marine life and our lives as a result
Our oceans are changing
(Image: Getty Images )
New research has exposed a significant and concerning change in our oceans. More than a fifth of the Earth's ocean has become darker over the past two decades.
This process takes place when changes to the ocean's top layer diminish the depths reached by sunlight. The study identified that a region exceeding 75 million square kilometres – the habitat for 90% of all marine life – experienced darkening between 2003 and 2022.
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Scientists from the University of Plymouth and Plymouth Marine Laboratory have scrutinised NASA satellite imagery and numerical models to determine the yearly fluctuations in the depth sunlight hits the Earth's oceans, reports the Manchester Evening News.
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They discovered that 21% of the global ocean had seen a darkening effect over the last two decades – with researchers warning that this could impinge on "the air we breathe, the fish we eat, our ability to fight climate change, and for the general health and wellbeing of the planet".
Dr Thomas Davies, associate professor of marine conservation at the University of Plymouth, explained: "There has been research showing how the surface of the ocean has changed colour over the last 20 years, potentially as a result of changes in plankton communities."
"But our results provide evidence that such changes cause widespread darkening that reduces the amount of ocean available for animals that rely on the sun and the moon for their survival and reproduction."
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"We also rely on the ocean and its photic zones for the air we breathe, the fish we eat, our ability to fight climate change, and for the general health and wellbeing of the planet. Taking all of that into account, our findings represent genuine cause for concern." For our free daily briefing on the biggest issues facing the nation, sign up to the Wales Matters newsletter here .
Satellite images are used to work out how much of the ocean has become darker
(Image: Getty Images )
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The study also discovered that over 9% of the ocean – an area comparable in size to the continent of Africa – has been impacted by a reduction in the sunlight-receiving layer of water, making it 50 metres shallower. Meanwhile, 2.6% has become more than 100 metres shallower.
In contrast, the research identified that approximately 10% of the ocean became brighter. While the exact effects of these alterations remain unclear, they have the potential to hugely affect marine life across the globe, experts warn.
Professor Tim Smyth, head of science for marine biogeochemistry and observations at Plymouth Marine Laboratory, remarked: "The ocean is far more dynamic than it is often given credit for.
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"For example, we know the light levels within the water column vary massively over any 24-hour period, and animals whose behaviour is directly influenced by light are far more sensitive to its processes and change.
"If the photic zone is reducing by around 50m in large swathes of the ocean, animals that need light will be forced closer to the surface where they will have to compete for food and the other resources they need.
"That could bring about fundamental changes in the entire marine ecosystem."
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The most noticeable changes in sunlight depth in the ocean were observed at the top of the Gulf Stream and around both the Arctic and Antarctic - areas undergoing the most extreme shifts due to climate change.
The study is published in the journal, Global Change Biology.