Science Weekly Into the photic zone: does a darkening ocean threaten marine life?
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Jun 5, 2025 In this engaging discussion, Tim Smyth, a Professor at the Plymouth Marine Laboratory, unveils alarming findings about the ocean's darkening trend. He explains how fading light in the photic zone, home to 90% of marine life, threatens delicate ecosystems and vital biological processes. The podcast highlights the impact of this phenomenon on essential migrations, particularly of copepods, which play a crucial role in ocean health. With satellite imaging revealing significant reductions in ocean clarity, Smyth urges listeners to consider the implications for marine species and their habitats.
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Copepod Daily Migration
- Copepods perform the largest daily migration on the planet, moving vertically in huge numbers.
- This migration helps them feed and avoid predators within the photic zone.
Ocean Darkening Shrinks Habitat
- Over 21% of the global ocean has darkened, shrinking the photic zone by over 50 meters in large areas.
- This darkening equates to habitat loss comparable to the size of Africa, impacting marine life significantly.
Marine Life Guided by Low Light
- Marine life relies on very low light levels to guide crucial behaviors like vertical migration.
- Zooplankton detect these faint cues to balance feeding and predator avoidance.