Tuna carbon ratios reveal shift in food web

The ratio of carbon isotopes in three common species of tuna has changed substantially since 2000, suggesting major shifts are also taking place in the phytoplankton populations that form the basis of the ocean's food web, according to a new international study. Much of the change occurring in phytoplankton physiology and species composition may be driven by increased ocean stratification, an impact of climate change, the study suggests.