A Canadian-led study suggests that plant and animal life in the world's oceans will drop steadily and consistently as the climate warms.
The study uses marine climate models to predict what will happen to the crucial global food source under different amounts of warming.
Derek Tittensor of Dalhousie University in Halifax says that the effect was pretty consistent.
The study predicts that for every degree oceans warm they produce, on average, five per cent fewer plants and animals.
That means that the world is on track to lose about 17 per cent of the productivity in oceans if there are no significant reductions in greenhouse gases.
Tittensor says the effect is concentrated in bigger fish caught for food.