Carbon dioxide stimulates lake primary production

Gross primary production (GPP) is a fundamental ecosystem process that sequesters carbon dioxide (CO 2 ) and forms the resource base for higher trophic levels. Still, the relative contribution of different controls on GPP at the whole-ecosystem scale is far from resolved. Here we show, by manipulating CO 2 concentrations in large-scale experimental pond ecosystems, that CO 2 availability is a key driver of whole-ecosystem GPP. This result suggests we need to reformulate past conceptual models describing controls of lake ecosystem productivity and include our findings when developing models used to predict future lake ecosystem responses to environmental change.