Using data collected by underwater robots, researchers have confirmed the presence of one of the world’s largest marine dead zones in the Gulf of Oman, an area that has been largely off-limits to scientists in recent decades due to piracy and geopolitical tensions. The dead zone, an area in the ocean with almost no oxygen, encompasses nearly the entire 63,700-square-mile Gulf of Oman, according to new research in the journal Geophysical Research Letters.
Scientists first discovered the Gulf of Oman dead zone in the 1960s, and collected data on it again in the 1990s. But no comprehensive surveys had since been conducted of the dead zone, ocated between India, Iran, and Oman. From 2015 to 2016, researchers at the University of East Anglia (UEA) and Oman’s Sultan Qaboos University deployed underwater robots known as Seagliders, which surveyed the Gulf of Oman for eight months, sending scientists data about oxygen levels and ocean currents via satellite.
The findings indicate that since the 1990s, the gulf’s dead zone has undergone a “dramatic increase” in both size and severity. The dead zone is now comprised entirely of anoxic conditions, meaning no oxygen is present, or suboxic conditions, with low oxygen levels. Researchers said the main cause of the expanding dead zone is warming waters, which increase the growth of bacteria and reduce the oxygenation of the Gulf through mixing of ocean layers. Growing levels of pollution and the runoff of nitrogen and phosphorous from fertilizers also have contributed to the expansion of the dead zone.
“Our research shows that the situation is actually worse than feared,” the study’s lead author, Bastien Queste, a marine biogeochemist at UEA, said in a statement. “The area of dead zone is vast and growing. The ocean is suffocating. 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.”