Into the photic zone: does a darkening ocean threaten marine life?

Science Weekly

The Guardian

Science

4.2 • 938 Ratings

🗓️ 5 June 2025

⏱️ 17 minutes

🔗️ Recording | iTunes | RSS

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Summary

Vast areas of the ocean are getting darker, according to research based on satellite imaging. Marine ecosystems are governed by faint light changes – from mass nightly migrations to coral spawning cycles – so what happens when that light begins to fade? Ian Sample talks to Prof Tim Smyth from the Plymouth Marine Laboratory about why this darkening is happening and how life in the ‘photic zone’ – the sunlit upper layer that is home to 90% of marine organisms – could be profoundly affected Planet’s darkening oceans pose threat to marine life, scientists say. Help support our independent journalism at theguardian.com/sciencepod

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1:19.1	Today I want to take you into the photic zone.
1:28.1	Imagine you're a coperod, a tiny crustacean, 2 millimetres long, floating 200 metres below the surface of the Atlantic.
1:38.6	As the sun blazes far overhead, you're safe down here in the gloom.
1:45.0	But as the daylight starts to dim and the sun edges over the horizon, you're getting hungry
1:51.0	and ready to move.
1:54.0	When your light sensors tell you it's time, you push upward, flapping bristled antennae.
	...

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