Something enormous had been hiding beneath the Atlantic Ocean – leaving scientists surprised and amazed when they saw it

Imagine discovering that there was a great strip of land between Scotland and Iceland that nobody had noticed before. Sounds ridiculous, doesn’t it? And yet, something rather similar has happened beneath the waves of the South Atlantic Ocean. 

In 2022, researchers described a vast network of previously overlooked reef habitats running along Brazil’s eastern coast. The underwater ‘bridge’ connects two bigger, better-known reef systems – the Amazon Reef System to the north and the Eastern Brazilian Reef System to the south. 

• It’s the same size as Japan, can be seen from space and is a UNESCO World Heritage Site – and it’s teeming with thousands of species

Previously, these two reef systems were thought of as two separate worlds, divided by a 1,000km stretch of unremarkable seabed. Not so. It turns out this stretch is home to a rich patchwork of rocky outcrops, coral colonies, sponges and more. 

• This coral reef gets bombed every 62 minutes. And it’s changing the way the ocean sounds
• “The fish life has exploded": 400,000 corals planted on dying reef in Bali. What happened next was remarkable

Together, the three systems form a vast, interconnected reef ecosystem stretching for around 4,000km – about the distance from London to Cairo. This makes it one of the world’s largest semi-continuous tropical marine ecosystems. 

• They look like toast racks, ping-pong balls and giant vases, range from pea-sized to car-sized – and are animals that have been on Earth for millions of years

Researchers explored the area, revealing a surprisingly rich array of habitats and marine life. At shallower sites, divers encountered colourful sponges, coral colonies and reef fish, including the brilliantly coloured queen angelfish, with its electric-blue markings and bright yellow tail. Some rocky formations were carpeted in great star corals, which form chunky, rounded colonies resembling underwater boulders. Look closely and their surfaces are dotted with fleshy, star-shaped polyps. 

Further down, remotely operated vehicles explored deeper seabeds, where rocky outcrops and sandy patches supported abundant sponges and delicate soft-bodied corals known as octocorals. These have eight feathery tentacles and flexible supporting structures, giving some colonies the appearance of miniature underwater trees.  

Together, these patchy habitats cover an area roughly the size of Belgium. And they provide a vital function. 

Reef organisms need to move between populations to maintain genetic diversity, recolonise damaged habitats and sustain healthy populations. Many reef species disperse as planktonic larvae, carried by ocean currents before settling on suitable seabed. But the distance between the Amazon and Eastern Brazilian reef systems was thought to pose a barrier to this movement. 

• Coral reefs guide: what is coral and coral bleaching, and species to spot

The newly identified habitats may help to bridge that divide. Researchers think they may act as ecological stepping stones, providing places for organisms to settle and reproduce along the way. 

This has important implications for conservation. Recognising these habitats as one interconnected system changes how the region needs to be understood and managed. Damage to one part of the system could have repercussions far beyond the immediate area. And there is one particularly pressing threat: oil exploration. 

In October 2025, Brazil’s state-owned oil company, Petrobras, began exploratory drilling less than 40km from the Great Amazon Reef System. In January 2026, more than 15,000 litres of drilling fluid leaked into the sea. Petrobras said the fluid posed no environmental threat, but Brazil’s environmental agency, Ibama, disagreed. Petrobras was subsequently fined 2.5 million reais. 

The greater concern is what might happen if an accident released crude oil from the well itself. A major spill could be devastating for the reef, with ocean currents potentially carrying pollution over considerable distances. 

We have only just begun to appreciate what lies beneath these waters. The challenge now is to make sure it survives long enough for us to discover the rest. 

• Huge concrete-like cubes were submerged off the coast of Britain. One year later, they’re teeming with creatures
• 5,000 years ago, these forests drowned. Now they're thriving reefs – home to oysters, sponges, sharks, rays and turtles
• It's the length of Africa, home to more than 2,000 marine species—many found nowhere else on Earth—and one of the world's largest underwater forests