Deep sea life is more connected than we ever realized

For years, the deep ocean has been painted as Earth’s final frontier – a shadowy, silent place that is cut off from the rest of the world. But new research is showing that this picture isn’t quite right. 

Life in the deep sea may not be as cut off as we thought. In fact, it’s connected – really connected.

A sweeping new study reveals that brittle stars – those spiny, ancient relatives of starfish – have quietly been traversing entire oceans for millions of years. They’ve been linking ecosystems across the globe, from Iceland to Tasmania, all without anyone noticing.

Meet the unexpected world travelers

Brittle stars are found on every ocean floor, from the sunlit shallows to the abyssal plains more than 11,500 feet down. They’re tough, old creatures, with some lineages dating back over 480 million years.

Brittle stars are also surprisingly mobile – in their own way. While they don’t swim, fly, or walk great distances, their larvae do the traveling. 

The larvae are packed with yolk, which keeps them alive for a long time as they drift slowly along deep-sea currents. This gives them a passport of sorts – one that lets them cross enormous distances and eventually settle in completely different parts of the world.

Life connected in the deep sea

What makes this discovery so surprising is how different it is from what we know about life in shallow water. 

In coastal and surface ecosystems, temperature acts like a boundary. It shapes where marine animals can live and where they can’t. Warm-water species stay in the tropics, while cold-water species stay near the poles.

But in the deep sea, the temperature doesn’t change much. It stays cold, quiet, and relatively stable. That stability makes it easier for deep-sea species to spread out over huge distances and still survive.

Study lead author Dr. Tim O’Hara is the senior curator of marine invertebrates at Museums Victoria Research Institute.

“You might think of the deep sea as remote and isolated, but for many animals on the seafloor, it’s actually a connected superhighway,” said Dr. O’Hara.

“Over long timescales, deep-sea species have expanded their ranges by thousands of kilometers. This connectivity is a global phenomenon that’s gone unnoticed, until now.”

Secrets of brittle stars

This was the most comprehensive look yet at brittle stars and how they’ve moved around the planet. The researchers analyzed DNA from 2,699 specimens stored in 48 natural history museums around the world. 

The samples were collected during 332 research expeditions, some of them decades old.

The team discovered that many brittle star species in one part of the world are closely related to those in another. For example, species found off southern Australia are genetically similar to those living off the coast of the North Atlantic – half a world away.

“These animals don’t have fins or wings, but they’ve still managed to span entire oceans,” said Dr. O’Hara. “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.”

The connected deep sea is vulnerable

Despite how connected the deep sea appears, it’s not all the same. Different regions still have unique species, shaped by extinction events, environmental changes, and geological features on the seafloor. 

In some places, brittle star populations have been isolated for long periods. In others, they’ve migrated far and wide.

That’s where the concern starts to grow. The deep sea might be connected, but it’s also vulnerable.

“It’s a paradox. The deep sea is highly connected, but also incredibly fragile,” said Dr. O’Hara. “Understanding how life is distributed and moves through this vast environment is essential if we want to protect it, especially as threats from deep-sea mining and climate change increase.”

A global system in the ocean

Much of the genetic material used in this research came from museum collections – some stored for decades before being used in this study. 

The study brought together more than 40 institutions, including natural history museums, universities, and marine science organizations. 

“This is science on a global scale,” said Lynley Crosswell, CEO and Director of Museums Victoria. “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.”

This discovery doesn’t just reshape how we think about brittle stars. It forces us to rethink how life works in one of the most mysterious parts of our planet. 

The deep sea isn’t a quiet, disconnected wasteland. It’s a global system – one that’s more dynamic and more at risk than we ever knew.

The research is published in the journal Nature. 

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