A UM team identified a special isotopic imprint left by photosynthetic communities that may help scientists trace the importance of these communities in the broader ocean carbon cycle. “Our findings revealed that our basic understanding of these signatures in the ocean was incomplete,” says researcher Hilary Close.

They found that phytoplankton, which can live as much as 150 meters below the ocean surface, and the carbon isotope ratios in their cells vary between the top layer of the ocean, where sunlight reaches and the deeper, low-light areas of the ocean. The variations in carbon isotope ratios were as large as those in the geologic record that have been attributed to major global carbon cycle events. 

• Hilary Close