(CNN) -- The chemistry of the world's oceans is changing at a rate not seen for 65 million years, with far-reaching implications for marine biodiversity and food security, according to a new United Nations study released Thursday.

"Environmental Consequences of Ocean Acidification," published by the U.N. Environmental Program (UNEP)," warns that some sea organisms including coral and shellfish will find it increasingly difficult to survive, as acidification shrinks the minerals needed to form their skeletons.

Lead author of the report Carol Turley, from the UK's Plymouth Marine Laboratory said in a statement: "We are seeing an overall negative impact from ocean acidification directly on organisms and on some key ecosystems that help provide food for billions. We need to start thinking about the risk to food security."