An endangered bramble shark has been recorded in UAE waters for the first time – after the sea floor-dwelling fish swam over to a submersible with researchers onboard.
The species, Echinorhinus brucus, was spotted at a depth of about 850 metres off the east coast, during an expedition led by NYUAD scientists.
Experts hailed the sighting, saying it shows how much remains to be learnt about the UAE’s marine environment.
John Burt, an associate professor of biology at NYUAD, told how the fish approached the team's submersible on the seabed about 80 kilometres from the shore.
“Almost as soon as we landed, this massive shark swam up to look at us,” said Prof Burt.
“Because it's pitch black, if there's any light down there, any organism can see it from a long distance away.
“They're curious. They popped up to see what we were doing.”
Bramble sharks are quiet creatures and live typically close to the sea floor at depths of up to 900m. This one was recorded off the edge of the continental shelf.
Harmless to humans, they are usually black or brown and can grow more than 3m long. They have two small dorsal fins at the back and thornlike denticles – toothlike structures.
In 2020, the International Union for Conservation of Nature, a global authority on the status of the natural world, classified the bramble shark as endangered, due in part to targeted and incidental catches.
Exciting discovery
Footage from the submersible shows the bramble shark moving slowly across the sea floor, with the submersible overhead.
“What's really exciting about that shark is that it has never been recorded in the UAE before,” said Prof Burt.
He said it wasn’t surprising they hadn’t been seen before, as the east coast is very shallow. However, they are present in the Arabian Sea.
“It's not just an individual,” he said. “It is a population of them that occur out there that we didn't even know existed.”
The discovery came during an expedition on the OceanX research vessel, OceanXplorer, in December. It is equipped with underwater submersible craft along with remotely operated vehicles capable of exploring depths up to 6,000 metres and acoustic mapping sonars.
Prof Burt and his team from the NYUAD Marine Biology lab were there chiefly to study a mysterious 144m-deep reef discovered about 30km off Fujairah’s coast in 2022.
The reef was first explored by Simon Nadim, a Fujairah-based technical diver. Technical divers explore deeper waters than scuba divers.
Initially, Mr Nadim thought it was a wreck. Instead, he found a remarkable formation of corals not typically encountered at that depth in these waters.
This is known as the mesophotic zone and it is thought the reef could be home to unique species.
Mr Nadim also took part in the OceanX expedition.
“We call it the twilight zone because it is very much like the sun has just set and there's just enough light there,” said Prof Burt.
Footage shows how the submersible was lowered off the OceanXplorer, before slowly descending and using its powerful lights to penetrate the darkness as the reef looms ahead.
“You can see rocks actually appearing out of the sea bottom. And on those rocks, you start to see the corals appearing,” said Prof Burt.
It covers an area of about 100m by 50m square, with a ridge of rock that rises to 4m above the sea floor, before it “slowly tapered” back down. Fish use this as a habitat for shelter and food.
“That large rocky ridge had a tonne of stuff growing on it,” said Prof Burt.
More than 80 coral specimens were collected. These included rare black corals; hard corals – the colourful ones people typically think of; and soft corals. It is believed many are new for the UAE and some are thought to be new to science and could even be endemic – found nowhere else.
“It is amazing for me as a scientist to be able to get down there and not only see it with my own eyes as the second person in the world to see this, but rather to be able to spend six hours doing detailed surveys of the site. We literally saw every coral that was on that reef.”
Unravelling marine mysteries
Coral reefs are crucial ecosystems and are a lifeline for many species. But they are under pressure from a variety of issues, from warming seas to pollution.
Prof Burt said initially it was thought these deeper reefs could provide support to corals in shallow waters as a sort of “refuge from climate change” but it is now emerging they could be separate ecosystems.
“We didn't even know these existed [in UAE waters] until November 2022,” he said.
“If you have a unique ecosystem, you should be protecting it but you cannot manage something that you don't understand.”
“Much more remains to be discovered about the reef, such as why the colonies are smaller when compared to similar reefs in other parts of the world. Was there a past disturbance event? Why is the temperature warmer by the reef? Do marine conditions play a role such as hot salty water that comes from the Gulf?
“These are unexplored questions that we're going to start looking into,” said Prof Burt.
State-of-the-art exploration vessel anchors in Dubai
The site is also close to port anchorages, while dredging work has cut a channel very close to the site, showing how vulnerable it is.
“It's eerie how much it came to impacting that reef,” said Prof Burt.
“But what I can say is that this is a highly vulnerable site … and important ecosystem. This is very significant.”
The team scoured the area looking for other reefs during the 10-day expedition completing several missions in the submersibles. Prof Burt said the sea floor has ridges and rises that take time to chart.
Other finds included the fossilised remains of “many thousands” of mangrove roots.
Watch: Diver finds mysterious 'Mars-like' reef 144 metres off UAE's east coast
Prof Burt said it is believed these are the “remnants of mangrove populations” at the mouth of the Gulf of Oman during the last ice age, when there was no Arabian Gulf. This could shed light on where the coast was then.
Mr Nadim said it was a “mind-blowing experience” to be on the OceanX vessel and was grateful his dive in 2022 helped open up new gateways of scientific exploration.
He is now deploying his diving knowledge to try to pinpoint more deepwater reefs, showing how academics, researchers and divers can combine knowledge.
Prof Burt's team was just one of several onboard the OceanX vessel with others conducting separate studies of the UAE's environment.
OceanX is supported by Dalio Philanthropies which in November also granted $1 million funding boost to researchers at NYUAD to support efforts to protect the Arabian Gulf’s coral reefs against rising ocean temperatures.
OceanX science programme director Mattie Rodrigue said the OceanX team was responsible for high-resolution mapping of more than 1,250 square kilometres.
She also highlighted the significance of Prof Burt work. “For the first time, mesophotic and deep sea corals were discovered and studied in the UAE,” said Ms Rodrigue.
“This tremendous achievement we hope will inspire research for NYUAD and the Burt lab for years to come, especially given the unique warm, saline conditions of UAE waters and the ability for these corals to survive and thrive in that extreme environment,” she said.
