"Phytoplankton are the base of the marine ecosystem. It's the fuel on which it runs . Changes in phytoplankton abundance will ultimately affect everything higher in the food chain from tiny little zooplankton all the way up to large whales, valuable fisheries and humans at the top."

"Phytoplankton live close to the surface of the ocean so they have access to sunlight, which they use to make sugars through photosynthesis. In the process, they produce about half the world's oxygen and remove carbon dioxide from the atmosphere."

But they also need nutrients to grow, Boyce said, and those are brought up from deeper waters by mixing. As the ocean surface gets warmer, it tends to form layers that no longer mix well with deeper waters. "That makes the ocean more stable, which limits the amount of nutrients delivered to phytoplankton and adversely affects their growth," Boyce added.

Besides forming the basis for the food chain, phytoplankton have a large effect on the carbon cycle, and therefore the stability of the global climate, the study said.