Humans continue to transform the global nitrogen cycle at a record pace, reflecting an increased combustion of fossil fuels, growing demand for nitrogen in agriculture and industry, and pervasive inefficiencies in its use. Much anthropogenic nitrogen is lost to air, water, and land to cause a cascade of environmental and human health problems.

The accumulation of nitrate in freshwater and coastal marine ecosystems is one of the consequences of the worldwide production of artificial fertilizers. Here it is shown that nitrate accumulation in ecosystems shows consistent and negative nonlinear correlations with organic carbon availability, along a continuum from soils, through freshwater systems and coastal margins, to the open ocean.