Ecosystem nitrate flows

Nitrate accumulation in aquatic environments, largely a result of the use of artificial fertilizers, causes both environmental and public health problems. Philip Taylor and Alan Townsend now demonstrate a consistent inverse relationship between nitrate and organic carbon concentrations across soils, freshwater ecosystems and the ocean, including ecosystems that experience substantial nitrogen loading. They find that this pattern can be explained by carbon to nitrate ratios that influence nitrate accumulation by regulating the microbial processes coupling dissolved organic carbon-and-nitrate cycling. These results may provide a testable framework for unravelling the fate of nitrate — and the influence of human interventions — in ecosystems across the world. [Letter p. 1178]