Global warming could starve oceans of oxygen: study

By Alister Doyle, Environment Correspondent

OSLO (Reuters) - Global warming could gradually starve parts of the tropical oceans of oxygen, damaging fisheries and coastal economies, a study showed on Thursday.

Areas of the eastern Atlantic and Pacific Oceans with low amounts of dissolved oxygen have expanded in the past 50 years, apparently in line with rising temperatures, according to the scientists based in Germany and the United States.

And models of global warming indicate the trend will continue because oxygen in the air mixes less readily with warmer water. Large fish such as tuna or swordfish avoid, or are unable to survive, in regions starved of oxygen.

"Reduced oxygen levels may have dramatic consequences for ecosystems and coastal economies," according to the scientists writing in the journal Science.

The north of the Indian Ocean, along with the Arabian Sea and the Bay of Bengal, is also oxygen-low but the available data showed no substantial change in the size of the oxygen-minimum zone in recent decades.

Lothar Stramma, lead author at IFM-GEOMAR in Kiel, Germany, said there were signs the oxygen-low bands between 300 and 700 meters depths were getting wider and moving into shallower coastal waters.

"The expansion of the oxygen-minimum zones is reaching more to the continental shelf areas," he told Reuters. "It's not just the open ocean." That could disrupt ever more fisheries.

Problems of lower oxygen supply add to woes for the oceans led by over-fishing as the world struggles to feed an expanding population. A U.N. conference in 2002 set a goal of trying to reverse declines in fish stocks by 2015.