Air pollution doesn’t make breathing harder just for humans. In the Pacific, fish are choking, too.
In the Pacific Ocean, billions of tiny creatures are literally eating our air pollution.
The pollution starts out as an enormous cloud generated by industries in east Asia near Japan, China, the Koreas and Russia. For decades it has formed and floated into the coastal Pacific, where currents carry it thousands of miles away in a pattern that flows around Hawaii into the warm water tropics. That’s where phytoplankton go to town on the excess iron and nitrogen in the pollution.
Normally, dining tropical phytoplankton — the foundation of a food web on which all life there depends — are good because the activity actually creates oxygen near the water’s surface, as a new study released Monday explains. But as they gorge themselves on excess nutrients, they create organic matter that sinks into the deeper ocean and is feasted on by microscopic bacteria. That’s bad because the latter sucks away oxygen in warm ocean water that has less to start with.
“Many living organisms depend on oxygen that is dissolved in seawater,” said Taka Ito, an associate professor at Georgia Tech University and the lead author of the study published in Nature Geoscience. “So if it gets low enough, it can cause problems, and it might change habitats for marine organisms.”
That’s one way of saying it’s likely killing them by the thousands, lowering the potential catch of seafood on which much of the world depends.
Researchers have known for a long time that excess dust is falling on ocean coasts and that air pollution is making that problem much worse. But the study’s co-author, Athanasios Nenes, another Georgia Tech professor, said it is the first to show that strong currents carry it to the deep.
“People never thought that it gets transported thousands of miles away,” Nenes said in an interview Sunday. The only way to stop the process, he said, is to “control emissions of sulfur and nitrogen.”
Low-oxygen “hypoxic events” known as dead zones often occur near coasts. But Nenes said what’s happening in the Pacific is more scary. “We’re talking about a vast amount of deep ocean water being turned into a dead zone.”
Oxygen depletion was already identified by scientists as a problem because warm water holds less of it. But since the 1970s, it was happening more rapidly in the tropical Pacific, faster than rising temperatures could explain.
They developed a model that looked at the atmospheric chemistry and ocean circulation, according to a university statement.
The pair kept an eye on water temperature, ocean currents and oxygen levels and found a link. They drew a grim conclusion: “If the pollution continues to supply excess nutrients, the process of the decomposition depletes oxygen from the deeper waters, and this deep oxygen is not easily replaced.”
“The scientific community always thought that the impact of air pollution is felt in the vicinity of where it deposits,” said Nenes. “This study shows that the iron can circulate across the ocean and affect ecosystems thousands of kilometers away.”