Oceans are just as affected by global warming as the rest of the planet, and the effects of this phenomenon have accentuated over the past decades, scientists revealed in a report published in the journal Science.

As the temperature of the oceans rose, the quantity of oxygen absorbed by warmer waters diminished, which led to a significant expansion of the oxygen-depleted zones in central regions of the Atlantic and Pacific Oceans.

These zones, which are unable to support life, are rapidly expanding, warned team leader Lothar Stramma from the Leibniz Institute of Marine Sciences at the University of Kiel, Germany, saying oxygen levels have gone beyond critical for marine life.

According to the study, over the past 50 years oxygen levels have considerably declined in tropical oceans at a depth of 300 to 700 meters (985 to 2,300 feet), which had a substantial impact on marine life, and could have economic consequences as well if the phenomenon continues.

The tropical northeast Atlantic ocean seems to be more affected by the phenomenon, compared to the Indian Ocean, where the changes over the past 50 years have been less pronounced.

“Whether or not these changes in oxygen can be attributed to global warming alone is still unresolved,” Stramma said. “The reduction in oxygen may also be caused by natural processes on shorter time scale,” he continued.

Co-author Jane Sprintall, physical oceanographer at Scripps Oceanography and co-author of the study said that oxygen-depleted areas might move to coastal areas due to currents from the tropical oceans. “The width of the low-oxygen zone is expanding deeper but also shoaling toward the ocean surface,” Sprintall said.

The study, called “Expanding Oxygen-Minimum Zones in the Tropical Oceans,” includes data gathered over the past 50 years and appeared in the May 2 edition of the journal Science (requires subscription).