The planet’s largest oceanic dead zone is located in the Gulf of Oman and now covers an area of 165,000 square kilometers.
This region of the Arabian Sea records almost zero oxygen levels, making it impossible for most marine organisms to survive.
A study conducted in recent years confirmed that this oceanic dead zone turned out to be worse than expected.
According to the research led by scientist Bastien Queste, the area continues to expand and poses a serious environmental threat to those who depend on the ocean.
What is an oceanic dead zone?
Dead zones are aquatic regions almost devoid of oxygen, where marine life cannot survive.
This phenomenon occurs mainly near inhabited coasts, where human activity concentrates higher levels of pollution.
Since the 1970s, scientists have observed a dramatic increase in the number of these areas. By 2008, 405 dead zones had already been recorded worldwide.
According to a study published in the journal Science, the size of oxygen-depleted zones in open waters has quadrupled since the mid-20th century.
Coastal zones with very low oxygen have increased by 10 times in the same period.
The causes of deoxygenation
Oceanic dead zones are caused by two main factors:
- Excess of chemical nutrients: resulting from human activity that runs from land to rivers and coasts
- Climate change: alters ocean circulation and oxygen transport
- Algae growth: excess nutrients stimulate their excessive proliferation
- Decomposition: dead algae consume the available oxygen in the water
The United States National Oceanic and Atmospheric Administration noted that “nutrient pollution is the main cause of these human-created zones.”
The situation in the Gulf of Oman
Scientists have known about this oceanic dead zone since the 1960s, but recent research has revealed its dramatic growth.
To assess the situation, a team submerged two autonomous vehicles for eight months in the gulf.
The robots communicated via satellite to build a picture of the oxygen levels and the mechanisms transporting this element. The data showed that oxygen is almost non-existent in the region.
In the Gulf of Oman, oxygen concentrations are below 6 micromoles per kilogram. 120 micromoles are needed for the survival of various forms of marine life.
“The Arabian Sea is the world’s largest and densest dead zone,” stated Queste. “Our research shows that the situation is worse than feared, and the area is growing.
The ocean is suffocating,” he concluded.
Environmental consequences of this oceanic dead zone
The lack of oxygen causes hypoxia in marine animals, which cannot breathe normally. Those that cannot escape these zones die from suffocation.
Denise Breitburg, a scientist at the Smithsonian Environmental Research Center, noted that “the largest extinction events in Earth’s history were associated with warm climates and with oxygen deficiency in the oceans.”
Another serious problem is that in the absence of oxygen, the chemical cycle of nitrogen changes. This produces nitrous oxide, a greenhouse gas 300 times more potent than carbon dioxide.
