Pollution and global warming are pushing the world's oceans to the brink of a mass extinction of marine life unseen for tens of millions of years, a consortium of scientists warned.

Dying coral reefs, biodiversity ravaged by invasive species, expanding open-water "dead zones," toxic algae blooms, the massive depletion of big fish stocks -- all are accelerating, they said in a report compiled during an April meeting in Oxford of 27 of the world's top ocean experts.

Sponsored by the International Programme on the State of the Ocean (IPSO), the review of recent science found that ocean health has declined further and faster than dire forecasts only a few years ago.

These symptoms, moreover, could be the harbinger of wider disruptions in the interlocking web of biological and chemical interactions that scientists now call the Earth system.