Oxygen is life but underneath the global oceans, this essential gas is becoming scarce, threatening fish species and other aquatic creatures.
According to Xinhua, the Chinese news agency, scientists have found that the oxygen content of global oceans has been declining mainly because of human activities.
This could ultimately cause societal and economic harm.
Deoxygenation of the open ocean and coastal waters has lasted for at least the past half-century, largely because of human activities that have increased global temperatures and nutrients discharged to coastal waters.
The level of oxygen in all ocean waters is falling, with 77 billion tonnes or 2 percent having been lost since 1950, according to the study, reported by China’s news agency Xinhua.
Scientists around the world published on Friday their joint research paper in the journal Science, appealing for further research to assess the consequences and figure out remedies.
The research reviewed the downward trajectory of oxygen levels in increasing areas of the open ocean and coastal waters, and found that “oxygen-minimum zones in the open ocean have expanded by several million square kilometres.”
Meanwhile, hundreds of coastal sites now have oxygen concentrations low enough to limit the distribution and abundance of animal populations and alter the cycling of important nutrients, the study said.
Global warming is the primary cause of deoxygenation, while coastal systems also suffer from rising nutrient loads from agriculture, sewage as well as fuel combustion.
The scientists used numerical models to predict further oxygen declines during the 21st century even with ambitious emission reductions.
They warned that the expansion of deoxygenation could increase greenhouse gas production, reduce biodiversity, and also negatively affect food security.
“This is a problem we can solve. Halting climate change requires a global effort, but even local actions can help with nutrient-driven oxygen decline,” one of the co-authors Denise Breitburg was quoted by the Guardian.
The prediction models of ocean deoxygenation should be improved, scientists suggested, adding that feedbacks to climate as well as the link between low-oxygen zones with fisheries should also be studied.