Unlike BP's, natural oil seeps can help sea life | Reuters

(Reuters) - Some marine life thrives on oil bubbling up naturally from the seabed even though it cannot cope with giant single leaks like from BP's ruptured well in the Gulf of Mexico, experts say.

Natural seeps from thousands of spots from the Pacific Ocean to the North Sea account for about 45 percent of all oil entering the oceans in a typical year, according to the U.S. National Academy of Sciences. The rest is from leaks caused by people.  [How, specifically, was this percentage calculated?  If we've only seen 1 percent of the sea floor, who is monitoring the flow rate of all of those natural seeps?]
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Jernelov estimates BP's leak, the worst in U.S. history, at 250,000 to 400,000 tonnes by early this month, compared with 140,000 tonnes leaking naturally every year from seeps in the seabed in the Gulf of Mexico alone.
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"We've seen about 1 percent of the sea floor. When you start finding oil floating around you think it's from a tanker. But a significant amount comes from below," said Martin Hovland, an expert on seeps at the University of Bergen in Norway.

He said late Norwegian explorer Thor Heyerdahl was probably wrong to blame human pollution for oil spotted in mid-Atlantic from his Ra raft in 1969 and 1970. The oil, some encrusted with barnacles and algae, may well have been from a natural seep.

And Hovland said seeps might be far more important in the food chain than believed, perhaps drawing humpback whales to the Guaymas Basin in the Gulf of California where thick mats of bacteria and other organisms carpet the seabed near seeps.

Seeps might also explain why the North Sea, rich in oil and gas, has more fish than the nearby Irish Sea, he said.