The 500-year-old secret hidden beneath the fjord

The fjord has been keeping a secret

Down in the freezing, pitch-black depths where sunlight never reaches, a hidden treasure has been growing quietly. Estimated to be hundreds of years old, these deep-sea structures have remained unseen by human eyes. In 2025, we sent a remote-operated underwater vehicle (ROV) down to the fjord floor to map our marine biology. What was found changes our understanding of the West Norwegian Fjords forever.

When the lights hit the bottom

Before the dive, we assumed the ROV would likely find communities of deep-sea sponges and seapens. Instead, as the ROV's lights pierced the dark, the screens in the control room lit up with massive, complex, and healthy coral reefs. As marine biologist Christiane Todt recalls:

"We were filming the sea floor and we saw some sponges and lots of different fish, but suddenly – and this was really surprising – there was this stone coral reef with a lot of living coral, and it was quite large. It was really great to see something like that 100 kilometres from the open ocean. This is really special."
— Christiane Todt

Remarkably, these thriving deep-sea cities are located right in the middle of our most famous waterways, situated exactly between the iconic Seven Sisters waterfalls and the town of Geiranger. "If you take a cruise on Geirangerfjord, you probably will pass right over those reef areas," Todt notes.

Down in the dark, millimetre-sized animals have spent centuries building limestone structures up to 4 metres tall. These pale, ghostly builders – primarily the Eye Coral (Desmophyllum pertusum) – prove that life does not need the sun to build a city; it only needs the dark current and time.

Finding such massive structures only in 2025 was a humbling moment. It is a stark reminder that our understanding of the fjord's biodiversity is still in its infancy. After all, unmapped does not mean empty, and finding these reefs poses a crucial question about how we approach future development with the wisdom of uncertainty.

A bustling underwater metropolis

The research revealed that this hidden metropolis stretches across the protected World Heritage area. While massive Eye Corals build their foundations beneath the famous waters of Geiranger, the deep sill of the neighbouring Sunnylvsfjorden hosts a different kind of magic. Here, Sea Trees rise like a vibrant forest, and deep-sea sponges filter the freezing water. Far from being just cold water, our protected fjords are a crowded neighbourhood where every species has a job.

Life extends far beyond the hard rock walls. Even the flat, seemingly barren expanses of soft mud are conquered by delicate colonial animals that look like old-fashioned quill pens or living feathers.

"To have these oases of life where you can find smaller organisms that can thrive... they can have a spillover effect. You have fish coming there, getting food, going out and being eaten by fish in other places. It's really a hot spot for biodiversity, which is important for the rest of the ocean."
— Ørjan Sørstrønen Vabø

The fjord's nursery (barnehage)

This hidden metropolis is not just a scientific curiosity; it is the lifeblood of our local traditions.

The complex reef structures act as a vital nursery – a barnehage – for the fjord. Small fish use the countless hiding spots to shelter from strong currents and predators while they grow. For generations, local fishermen have sought out the coral area, specifically known as a good zone for catching Lange (Ling), Brosme (Tusk), and Uer (Redfish). They have essentially been harvesting from the roof of a coral nursery – a delicate balance that makes us reconsider exactly where our dinner actually sleeps.

For local fishing enthusiast Tor Hole, the sheer scale of this living city was a revelation. "It was a surprise to me that there were multiple species, on such a large scale, and in different colours," Tor explains. He has spent a lifetime floating right above this hidden wonder:

"I started fishing with my grandfather when I was 8–10 years old. We didn't have a motor back then, so we had to row out toward the Seven Sisters."
— Tor Hole

Our fishermen aren't just harvesting; they are actively guarding these areas. Because locals like Tor Hole use traditional, passive fishing methods like nets, handlines, and trolling, the researchers observed no obvious fishing damage to the reefs. Furthermore, local fishermen are relieved that large-scale industrial fishing has stopped in the fjord.

As Tor points out about the industrial ships that used to empty the fjord, "if the herring disappears, you have no other fish either."

Knowing this ecosystem exists forces us to rethink how we manage the water. While the inner fjord provides a safe haven, the migratory routes of these fish through outer gateways like Storfjorden are still exposed to industrial fishing. It begs the question: does it make sense to strictly guard the living room if we allow bulldozers in the hallway?

Furthermore, even local activities on land – like road construction or rock dumping – can send fine dust travelling for kilometres underwater, smothering the fragile polyps. Maybe we can look for a balance between man and nature, by taking precautions not to bury these beautiful living creatures?

Expanding our heritage

When the West Norwegian Fjords received World Heritage status, we did not even know these 500-year-old corals existed. Our Outstanding Universal Value (OUV) was based on the majesty we could see above the surface.

This discovery suggests that the area is even more unique on a global scale than UNESCO originally realised. Our World Heritage status was based on what we could see. Now that we know about the biological wonder in the deep, our responsibility to the world must go deeper, too.

The hidden treasure has been found. Now, it is up to all of us to make sure it thrives for another 500 years.

Watch "Exploring the Ancient Coral Kingdom of Geirangerfjord & Sunnylvsfjord" to continue the story.

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