Just as oxygen is essential to all plant and animal life on land, it is necessary to sustain life in our oceans. However, there are certain regions around the world where oxygen concentrations reach very low levels. They are known as “oxygen minimum zones” (OMZ), or as they are more frequently called, “dead zones.”
And as the name implies, in these dead zones, few, if any plants or sea creatures can survive. They emerge in ocean depths ranging from 650 to 2,600 feet (200 to 800 meters), typically caused by climate change-induced ecological shifts or human pollution, quite often from chemical runoff. This encourages algae growth that in turn, sucks up the oxygen.
Many people are more familiar with the “dead zone” in the Gulf of Mexico, off the shores of Louisiana and Texas. Last year, the dead zone was estimated to cover more than 10,000 square miles (26,000 square kilometers).
The Gulf of Mexico’s dead zone is caused by the nitrogen-rich agricultural runoff in the Midwest farm belt. This fertilizer runoff, along with human and animal wastewater, fuels the growth of algae.
When the algae die, it sinks to the bottom and decomposes, sucking the oxygen from the water and making it uninhabitable for fish and other marine organisms.
But the absence of oxygen also alters the local nitrogen cycle, causing nitrous oxide emissions — which is a greenhouse gas 300 times more powerful than carbon dioxide.
The Gulf of Oman dead zone is huge
Remote-control submarines were used to map the extent of the massive area of OMZ in the Gulf of Oman and found the dead zone spanned a chilling 63,700-square-mile (roughly 165.000 square kilometers) area in the Gulf of Oman.
The OMZ is nearly devoid of oxygen. That’s an area comparable to the surface of Florida (170,305 square kilometers), and over two times larger than Scotland (80,077 square kilometers).
While a fairly significant OMZ has existed in the Gulf of Oman for decades, the last time it was actually surveyed was in the 1990s. Because of its location – it connects the Arabian Sea to the Persian Gulf – It has long been off-limits to researchers because of the region’s political instability and the threat of ocean piracy, according to Live Science.
In a research letter published in the journal Geophysical Research Letters on April 27, 2018, the study’s lead author, Dr. Bastien Queste, a research fellow in the School of Environmental Sciences at the University of East Anglia in Norwich, said, “The ocean is suffocating. All fish, marine plants and other animals need oxygen, so they can’t survive there.”
The researchers used two lightweight diving submarines, called Seagliders, capable of traveling thousands of kilometers and reaching depths of about 3,300 feet (1,000 meters). The survey took eight months, with the submersibles gathering data on oxygen levels and transmitting the data via satellite to the researchers.
According to the study, the team used computer models to visualize the ocean currents that circulated oxygen around the gulf from the Arabian Sea. They found that the oxygen-poor region had grown dramatically, and the scant oxygen formerly held in the depleted zone — based on data from the 1990s — had drained significantly, leaving bigger areas with no oxygen at all.
The results of the study are alarming
And with the dead zone still growing, the research letter says that unless this situation is addressed it could have drastic consequences for life both in and out of the sea.
“The take-home message is that standing on the beach looking out, the sea will look identical. You’re not going to notice the impact straight away, but things are changing incredibly rapidly and dangerously,” Dr. Queste told The National.
“It’s a real environmental problem, with dire consequences for humans, too, who rely on the oceans for food and employment,” Dr. Queste added.
