Methane formation in tropical reservoirs predicted from sediment age and nitrogen

Freshwater reservoirs, in particular tropical ones, are an important source of methane (CH(4)) to the atmosphere, but current estimates are uncertain. The CH(4) emitted from reservoirs is microbially produced in their sediments, but at present, the rate of CH(4) formation in reservoir sediments cannot be predicted from sediment characteristics, limiting our understanding of reservoir CH(4) emission. Here we show through a long-term incubation experiment that the CH(4) formation rate in sediments of widely different tropical reservoirs can be predicted from sediment age and total nitrogen concentration. CH(4) formation occurs predominantly in sediment layers younger than 6–12 years and beyond these layers sediment organic carbon may be considered effectively buried. Hence mitigating reservoir CH(4) emission via improving nutrient management and thus reducing organic matter supply to sediments is within reach. Our model of sediment CH(4) formation represents a first step towards constraining reservoir CH(4) emission from sediment characteristics.