Scientists have discovered that a “dead zone” in the Arabian Sea is larger than previously thought. Located in the Gulf of Oman between India, Iran and Oman, the dead zone is currently bigger than the area of Scotland and continues to grow, according to new research.
Although scientists have been aware of the dead zone for more than half a century, geopolitical tensions and piracy have prevented researchers from studying the area since the 1990s. A new study, conducted using underwater robots, has revealed that the situation is more serious than they realised.
Dead zones, also known as oxygen minimum zones, are parts of the ocean that lack oxygen. According to researchers, these areas occur naturally between depths of 200 and 800 metres in some parts of the world. Since all marine plants and animals require oxygen to survive, dead zones are unable to support marine life.
“[Dead zones] are a disaster waiting to happen—made worse by climate change, as warmer waters hold less oxygen, and by fertilizer and sewage running off the land into the seas,” lead author Bastien Queste, a marine scientist at the University of East Anglia (UEA) in the UK, said in a press release.
UEA’s School of Environmental Sciences conducted the research in collaboration with Oman’s Sultan Qaboos University. The findings were published in the journal Geophysical Research Letters on Friday.
Scientists explored the Gulf of Oman using two robots called Seagliders, which are around the same size as a small human diver but can reach depths of up to 1000 metres. The robots surveyed the area for eight months. Using satellite communication, the robots provided scientists with data concerning underwater oxygen levels and ocean mechanics, which affect the transport oxygen from one part of the ocean to another.
“Our research shows that the situation is actually worse than feared—and that the area of dead zone is vast and growing,” said Queste.
The team’s analysis showed that the entire Gulf of Oman – an area of over 130,000 square kilometres – is now in a suboxic or anoxic state.
“The ocean is suffocating,” Queste warned. “Of course all fish, marine plants and other animals need oxygen, so they can’t survive there. It’s a real environmental problem, with dire consequences for humans too who rely on the oceans for food and employment.”
By combining the data collected by the Seagliders with high-resolution computer models, researchers were also able to observe how the water’s oxygen levels change over time. They discovered fish become “squeezed” in a thin layer near the water’s surface as the dead zone moves up and down between seasons.
Queste said that he and his colleagues plan to conduct additional research to determine what is causing the growing oxygen minimum zone. “There are a number of things that could have contributed to the shift—the most major of which is very much tied to climate change,” Queste told Gizmodo.
Specifically, the team hopes to learn whether the problem stems from a decreasing amount of oxygen in the water or a higher number of marine plants and animals competing for the limited supply that is there.