Dec. 7 (UPI) -- The world's oceans are running out of oxygen, threatening many species of fish, says a new report from the conservation group IUCN.
"Urgent global action to overcome and reverse the effects of ocean deoxygenation is needed," said IUCN global marine and polar program director Minna Epps in a statement. "Decisions taken at the ongoing climate conference will determine whether our ocean continues to sustain a rich variety of life, or whether habitable, oxygen-rich marine areas are increasingly, progressively and irrevocably lost."
IUCN's study is the biggest study of its kind ever undertaken, combining the efforts of 67 scientists from 17 countries and was presented at the global climate summit in Madrid on Saturday.
The report pinpoints nutrient pollution and climate change as the major culprits in the depletion, which threatens several species of tuna, marlins and sharks -- larger species that have greater oxygen needs.
About 700 ocean sites tested now suffer from low oxygen, compared with 45 in the 1960s, and the amount of gas dissolved in the oceans declined by 2% between 1960 and 2010, the report says.
In some tropical locations, the oxygen loss is much higher -- as much as 40%.
Nutrient run-off due to pollution from chemicals like nitrogen and phosphorus has been a knwn factor in oceans' oxygen levels and remains a primary factor, but climate change has exacerbated the problem. As more carbon is released into the atmosphere, much of the heat is absorbed by the oceans, and the warmer water holds less oxygen.
The report estimates that if carbon emissions continue at their current rate, the world's oceans are expected to lose 3 to 4% percent of their oxygen by 2100, with worse rates of depletion in tropical regions of the world.