Underwater robots have revealed that the Gulf of Oman is hiding a deadly secret.

Researchers exploring the depths off the coast of Oman have discovered the largest ocean dead zone in the world, covering an area larger than the size of Scotland. The extent of the zone, which is growing, is likely to have been exacerbated by both climate change and runoff from the land, and could potentially threaten the fishing industry in the region.

“Our research shows that the situation is actually worse than feared – and that the area of dead zone is vast and growing,” said Dr Bastien Queste, who led the research published this week in Geophysical Research Letter. “The ocean is suffocating.”

“Of course all fish, marine plants and other animals need oxygen, so they can't survive there,” Dr Queste continued. “It's a real environmental problem, with dire consequences for humans too who rely on the oceans for food and employment.”

The underwater robots can collect data and send it back for months at a time. UEA

Researchers have known for some time that there has been a dead zone in the Gulf of Oman, but studying its extent in any detail has been wracked with difficulty. A dose of geopolitical instability mixed with a healthy dollop of piracy in the region has prevented research ships from conducting any work in the Gulf for the last 50 years.

This led scientists from the University of East Anglia and Oman’s Sultan Qaboos University to deploy underwater robots known as Seagliders to collect data autonomously. The robots were sent to survey the region down to 1,000 meters (3,280 feet) for a full eight months, sending back data via satellites. This enabled the researchers to then build up a detailed image of the oxygen levels as well as the underwater currents and mechanics that move that oxygen around at depth.

It revealed that the dead zone that sits between 200 and 800 meters (650 to 2,620 feet) beneath the surface is enormous, much larger than they thought it would be. It is currently comparable to the size of Scotland, making it the largest and thickest ocean dead zone in the world. And it’s growing.

This is not only an issue for any animals that want to live there, but has a knock-on effect on how other vital nutrients cycle through the oceans. For example, the researchers note how when oxygen is absent, it impacts how nitrogen moves through the water, too. This has a negative effect on plants, but can also lead to the production of nitrous oxide, which is roughly 300 times more potent than carbon dioxide.

Predictions show that over the next century, this zone is expected to grow. This means that the fishing industry needs to pay serious attention and change their management practices to maintain sustainability in the region now.