Global warming will disrupt four-fifths of the world's oceans by 2050 if greenhouse gas emissions keep rising, Reuter's quoted scientists as saying.
The situation is threatening fish that are the main source of food for a billion people.
Curbs on man-made emissions, however, would give marine life more time to adapt to warming conditions or for marine life from algae to cod to shift to cooler waters nearer the poles, they said.
"By 2050 around four-fifths of the ocean surface will be affected by ocean acidification and ocean warming," lead author Stephanie Henson, of the British National Oceanography Centre in Southampton, told Reuters of the findings.
Carbon dioxide, the main greenhouse gas, forms a weak acid in water. Currently, only about 10 percent of the oceans are under stress from the twin impacts of high temperatures and acidification, she said.
Cuts in greenhouse gas emissions, in line with goals set by almost 200 nations under a Paris Agreement on climate change in 2015, could limit the impact to two-thirds of the ocean by 2050, giving marine life more time to adapt, the scientists said.