Unexplored deep-sea worlds in the Caribbean revealed for the first time

Spectacular images reveal unique sea creatures and corals off Caribbean islands

The waters off the sparkling coasts of the British Caribbean territories have long been a mystery.

But now scientists, on their first expedition beyond the shallow waters of the islands, discovered an underwater mountain range, a huge “blue hole”, coral reefs apparently untouched by climate change and never-before-seen sea creatures.

Operating around the clock for the past six weeks, researchers have subjected cameras and other equipment to extreme water pressure, recording at depths of up to 6,000m.

To navigate the Cayman Islands, Anguilla and the Turks and Caicos Islands, they were forced to rely on decades-old maps with serious errors and entire areas missing.

The UK’s Center for Environmental, Fisheries and Aquaculture Sciences (CEFAS) shared its images and findings exclusively with BBC News.

The British government shares responsibility for protecting the islands’ nature and up to 90% of Britain’s unique species are found around these islands and other British Overseas Territories.

Scientists now say the race is on to protect this “relatively pristine” environment from the threats of climate change and pollution.

“This is the first step into environments that people have never seen, and in some cases never knew existed,” says Professor James Bell, who is leading the expedition on the British research vessel RSS James Cook with scientists from the three islands.

“Just yesterday we found some kind of swimming sea cucumber, and we still don’t know what it is,” he added, calling the diversity he saw “really, really amazing.”

The Cayman Islands, Anguilla and Turks and Caicos are home to 146 species that live only in these territories, and this research expedition is expected to add even more to the list.

The team documented nearly 14,000 individual specimens and 290 different types of sea creatures, although further scientific work is needed to confirm their findings.

They found a pelican eel with a glowing pink tail that flashes red to attract food, a barreleye fish with tubular eyes pointing upward to see the silhouettes of its prey, and a dragonfish with a glowing stalk under its chin.

Speaking to BBC News as the ship sailed over an unexplored underwater mountain called Pickle Bank, Bell said: “We don’t know how close we are to it. It’s quite difficult to map it without running the risk of running aground.”

The team eventually discovered that the mountain, located north of the island of Little Cayman, rises from 2,500 m (8,200 feet) deep to about 20 m (65 feet) below the sea surface.

The images reveal a bright blue, yellow and orange mountainside teeming with life – golden towers of coral growing next to corals that look like large brains.

The team filmed fish darting between gorgonian corals and orange jelly-like sea sponges near black coral.

They discovered one of the healthiest and most diverse reefs in the region, free from the ravages of hard coral disease plaguing the Caribbean. It is likely that this reef is protected, for the moment, by its depths and the steep mountain slopes.

Deep-sea, or mesophotic, reefs are also generally too deep to be affected by warming ocean temperatures – caused largely by climate change – which have damaged 80% of the planet’s corals since 2023.

Using deep-sea cameras and echo sounders lowered from the side of the ship, researchers mapped nearly 25,000 square kilometers (9,700 square miles) of seabed and captured 20,000 photos, including of glowing lanternfish and alien-like cephalopods.

“We know the surface of Mars or the Moon better than the surface of our own planet. You send a satellite around them and map them in a matter of weeks,” says Bell.

“We can’t do this for our ocean. We have to map it bit by bit using acoustic instruments on board ships,” he explains.

In the Turks and Caicos Islands, the team discovered something missing from existing nautical charts: an extremely steep 3,200 m (10,500 ft) mountain ridge extending 70 km (45 miles) along the seafloor, west of a place called Gentry Bank.

They were also amazed to discover a huge vertical sinkhole called the Blue Hole, 75 km south of a riverbank called Grand Turk, which was formed when a cave collapsed inward.

“Imagine pulling an ice cream scoop out of the sea floor. That’s what we saw: a crater about 300 m (980 ft) wide down to 550 m (1,800 ft) below sea level,” says Bell.

They believe its sheer walls could form the deepest blue hole in the Caribbean, rivaling Belize’s famous Great Blue Hole.

Usually nothing lives inside a blue hole, but cameras placed inside the new discovery show small sponges, a species of sea urchin called a large spatangoid, and various species of fish.

And 25 km north of Anguilla, researchers followed rumors spread by local fishermen that they had torn off pieces of coral while working. The team confirmed there was a 4 km (2.5 mile) reef with mosaics of corals growing in sponge “gardens”.

They also found black coral that could be thousands of years old, making it some of the oldest on record.

“This tells us that these environments are truly pristine and healthy,” Bell says.

Scientists are interested in these areas of deep water and steep mountains because they can channel nutrient-rich water to the surface, providing feeding grounds for animals or places to fish.

On board the vessel, CEFAS worked alongside a group of environmental experts from the Cayman Islands, Anguilla and the Turks and Caicos Islands who will use the findings to improve biodiversity management plans and find new fishing opportunities for island communities.

“Our islands literally grew out of the sea. But when it comes to our offshore environments, we’ve never really had a chance to find out what’s going on there,” Kelly Forsythe of the Cayman Islands Department of Environment told BBC News. Island governments joined the research under a project called the Blue Belt Program.

This work is expected to provide information to help the UK meet its legally binding commitments to the United Nations to protect 30% of the world’s oceans by 2030 in designated marine protected areas.

“Anyone can draw a box on a map and say, ‘That’s a marine protected area,’” Bell says.

“But unless you know what’s in it, you have no idea if it’s useful.”