Methane emissions from tank bromeliads in neotropical forests

Methane is a potent greenhouse gas(1). Methane concentrations above neotropical forests-the tropical forests found in Mexico, Central America, South America and the Caribbean-are high according to space-borne observations. However,the source of the methane is uncertain(2,3). Here, we measure methane fluxes from tank bromeliads-a common group of herbaceous plants in neotropical forests that collect water in tank-like structures-using vented static chambers. We sampled 167 bromeliads in the Ecuadorian Andes, and found that all of them emitted methane. We found a diverse community of methane-producing archaea within the watercontaining tanks, suggesting that the tanks served as the source of the methane. Indeed, tank water was supersaturated with methane, and 13C-labelled methane added to tank water was emitted though the leaves. We suggest that the bromeliad tanks form a wetland environment conducive to methane production. In conjunction with other wetlands hidden beneath the copy surface, bromeliads may help to explain the inexplicably high methane levels observed over neotropical forests.