A new Nature study published this week found that oxygen levels in worldwide oceans have dipped by more than 2% in the last half-century. While the change may seem small, scientists say even subtle shifts in gas levels can alter entire ecosystems.
“It’s significant,” said Rob Dunbar, an Earth science professor at Stanford University. “Anything with a gill is going to care and notice.”
Dunbar, who studies climate change in the tropics and Antarctica seas but who was not part of the Nature study, said the oxygen drop can have rippling effects across the deep blue. Larger marine animals, like sharks, require more oxygen, especially to carry out high-energy activities like feeding. Dropping oxygen levels create “no-go zones” for some sea creatures, leaving them fewer areas to eat and reproduce, Dunbar said.