Ocean acidification is likely to threaten the world's fisheries without sharp cuts to carbon dioxide emissions produced by human activities, the U.N. Environment Programme said Friday.

As CO2 emissions have risen, largely from the world's increasing appetite for burning fossil fuels, oceans have absorbed more and more of the greenhouse gas. That has shifted the chemistry of the seas, which are now 30 percent more acidic than they were before the start of the Industrial Revolution.

Scientists say that, without emissions cuts, the world's oceans could become 150 percent more acidic by the end of the century -- a rate of change that "has not been experienced for around 65 million years, since the dinosaurs became extinct," the UNEP report says.

It warns that shifting ocean chemistry could have a "considerable influence" on the world's marine life, including fisheries that supply the primary source of protein for more than 1 billion people worldwide.

"Although studies about the effects of ocean acidification on marine resources are comparatively new, early results indicate there is no room for complacency," the UNEP analysis says.

Studies show that more acidic water is harmful to sea creatures like oysters, corals, plankton and shellfish that grow hard shells made of a chalky mineral called calcium carbonate. If ocean water becomes too acidic, it can begin dissolving those shells, sometimes faster than creatures can rebuild them.

That's likely to send ripples up the food chain. Tiny swimming snails called pteropods, for example, appear to be particularly sensitive to ocean acidification, the report says. They are also an important food source for herring, salmon, whales and seabirds.

The UNEP study also highlights recent research that suggests young clownfish -- made famous in the Pixar movie "Finding Nemo" -- may find their ability to navigate the ocean degraded because higher CO2 levels affect the development of a special ear bone called an otolith that helps fish remain upright and sense motion. The young fishes' sense of smell may also be affected by acidification, changing the way they behave around predators.

Still, the UNEP study notes that the effects of ocean acidification aren't uniform. Some plankton species are more resistant to harm from higher CO2 levels, for example.

Still, UNEP Executive Director Achim Steiner said the new report was "yet another red flag being raised" about the growth of greenhouse gas emissions.

Ocean acidification, he said, "is a new and emerging piece in the scientific jigsaw puzzle, but one that is triggering rising concern."

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500