In a new global study, scientists have discovered that marine life in the deep sea is far more connected than previously thought.
By analysing the DNA of thousands of brittle stars – ancient, spiny animals found on seabeds across the world – researchers have revealed that these creatures have quietly migrated across entire oceans over millions of years, linking ecosystems from the poles to the equator.
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Discovering a deep-sea superhighway
Published in the journal Nature, the study examined the DNA of 2,699 brittle star specimens held in 48 natural history museums around the world. The findings show that, unlike species living in shallow waters, many deep-sea animals have the ability to spread over vast distances thanks to their unique biology and stable environment.
“You might think of the deep sea as remote and isolated, but for many animals on the seafloor, it’s actually a connected superhighway,” says Dr Tim O’Hara, senior curator of marine invertebrates at Museums Victoria Research Institute and lead author of the study.
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Over the past 100 million years, deep-sea brittle stars have used ocean currents to expand their ranges by thousands of kilometres. Their yolk-rich larvae can survive for long periods in cold, pressurised conditions, allowing them to drift across entire ocean basins and colonise distant regions.
This explains why populations in locations such as southern Australia and the North Atlantic share close evolutionary ties, O’Hara explains. “These animals don’t have fins or wings, but they’ve still managed to span entire oceans. The secret lies in their biology – their larvae can survive for a long time in cold water, hitching a ride on slow-moving deep-sea currents.”
Yet despite this connectivity, the deep sea is not a uniform world. Environmental changes, geographical barriers and extinction events have created pockets of unique biodiversity across the ocean floor.
As deep-sea ecosystems face growing threats from mining and climate change, understanding how species move and evolve becomes vital, says O’Hara. “It’s a paradox. The deep sea is highly connected, but also incredibly fragile."
Lynley Crosswell, CEO and director of Museums Victoria, adds: “This is science on a global scale. It demonstrates how museums, through international collaboration and the preservation of biodiversity specimens, can unlock new knowledge about our planet’s past and help shape its future.”
In pictures: deep-sea superhighway study
Top image: Basket sea star in Southeast Alaska. Credit: Getty
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