Oceans

Life in the oceans is at imminent risk of the worst spate of extinctions in millions of years due to threats such as climate change and over-fishing, a study showed on Tuesday.

Time was runningshort to counter hazards such as a collapse of coral reefs or a spread of low-oxygen "dead zones," according to the study led by the International Programme on the State of the Ocean (IPSO).

"We nowface losing marine species and entire marine ecosystems, such as coral reefs, within a single generation," according to the study by 27 experts to be presented to the United Nations.

"Unless actionis taken now, the consequences of our activities are at a high risk of causing, through the combined effects of climate change, over-exploitation, pollution and habitat loss, the next globallysignificant extinction event in the ocean," it said.

Scientists list five mass extinctions over 600 million years -- most recently when the dinosaurs vanished 65 million years ago, apparently after anasteroid struck. Among others, the Permian period abruptly ended 250 million years ago.

"The findings are shocking," Alex Rogers, scientific director of IPSO, wrote of the conclusions from a 2011workshop of ocean experts staged by IPSO and the International Union for Conservation of Nature (IUCN) at Oxford University.

Fish are the main source of protein for a fifth of the world's populationand the seas cycle oxygen and help absorb carbon dioxide, the main greenhouse gas from human activities.

OXYGEN

Jelle Bijma, of the Alfred Wegener Institute, said the seas faced a "deadly trio"of threats of higher temperatures, acidification and lack of oxygen, known as anoxia, that had featured in several past mass extinctions.

A build-up of carbon dioxide, blamed by the U.N. panel ofclimate scientists on human use of fossil fuels, is heating the planet. Absorbed into the oceans, it causes acidification, while run-off of fertilizers and pollution stokes anoxia.

"From a...