According to German researchers addressing delegates at a U.N. conference on climate change, the world’s oceans are becoming more acidic, which poses a threat to sea life and Earth’s fragile food chain.

Stefan Rahmstorf, head of Germany’s Potsdam Institute for Research into Climatic Effects, explained that as atmospheric levels of CO2 continue to build, the amount absorbed by the oceans also increases resulting in lower pH levels. These changes can affect coral reefs and the ocean’s food chain.

“The oceans are rapidly changing,” said Rahmstorf. “Ocean acidification is a major threat to marine organisms. Acidity is causing a major threat to coral reefs, on top of the bleaching effect that comes with warming.”

In a study titled The Future Oceans – Warming Up, Rising High, Turning Sour, Rahmstorf and eight other scientists warned that the world is witnessing, on a global scale, problems similar to the acid rain phenomenon of the 1970s and 1980s.