A series of marine threats — including warming waters, ocean acidification, the spread of oxygen-free dead zones, habitat loss, and overfishing — are pushing the world’s oceans toward a phase of mass extinctions not seen in millions of years, according to a new report by a consortium of marine scientists. In a report sponsored by the International Programme on the State of the Oceans (IPSO), the scientists said that the rates of coral loss, fish stock depletion, open-water “dead zones,” and toxic algae blooms have surpassed even the worst-case projections of just four years ago. And these trends could portend significantly wider disruptions on the world’s marine ecosystems; all five mass extinctions in the planet’s history — the most recent of which occurred 55 million years ago — were preceded by similar ocean conditions, scientists say. “The findings are shocking,” said Alex Rogers, scientific director of IPSO. “As we considered the cumulative effect of what humankind does to the oceans, the implications became far worse than we had individually realized.” The group called on states, regional bodies and the UN to establish programs to better conserve ocean ecosystems — particularly in the largely unprotected high seas that make up most of the planet’s oceans — and to reduce the greenhouse gas emissions driving ocean acidification and rising sea temperatures.