The amount of water in the Earth's oceans with zero oxygen has more than quadrupled over the past 50 years due to climate change, imperilling marine wildlife across the planet, a new research has found.
In coastal water bodies, including estuaries and seas, regions with low-oxygen have increased more than 10-fold since 1950, scientists said, adding that they expect oxygen to continue dropping even outside these zones due to global warming.
In the study, published in the journal Science on Friday, researchers said that the world must rein in both climate change and nutrient pollution to halt the decline of oxygen in Earth's oceans. The research was conducted by scientists from GO2NE (Global Ocean Oxygen Network), a new working group created in 2016 by the United Nation's Intergovernmental Oceanographic Commission.
"Oxygen is fundamental to life in the oceans," Denise Breitburg, marine ecologist with the Smithsonian Environmental Research Center and the study's lead author, said in a statement. "The decline in ocean oxygen ranks among the most serious effects of human activities on the Earth's environment."
The latest findings are alarming because nearly half of the oxygen on Earth comes from the ocean. But, due to the combined effects of climate change and nutrient pollution, the oxygen in the so-called "dead zones" plummets to levels so low that many animals suffocate and die.
In addition to these "dead zones," smaller oxygen declines can also affect growth in animals, hinder reproduction and lead to disease or even death. Low oxygen also can trigger the release of dangerous chemicals like nitrous oxide, which is up to 300 times more powerful than carbon dioxide, and hydrogen sulfide.
The researchers blamed climate change for the increasing low level of oxygen in oceans as warming surface waters make it harder for the gas to reach the deeper waters. And, when the entire ocean gets warmer, it holds less amount of oxygen.
When it comes to coastal waters, excess nutrient pollution from land creates algal blooms that drain oxygen as they die and decompose.
Researchers said that to keep low oxygen in check, people need to implement better septic systems and sanitation to protect human health and keep pollution out of the water. Cutting fossil fuel emissions can also slash air pollution.
"This is a problem we can solve," Breitburg said. "Halting climate change requires a global effort, but even local actions can help with nutrient-driven oxygen decline."
