Thursday, April 08, 2010, 4:30PM - 5:30PM
Full title: "Stoichiometric control of organic carbon-nitrate-phosphorous relationships from soils to sea."
Human creation of reactive nitrogen has risen an order of magnitude since the dawn of the Industrial Revolution. This dramatic reorganization of a global biogeochemical cycle has brought substantial benefits, but increasingly causes detrimental outcomes for both people and ecosystems. One such problem is the accumulation of nitrate and bioavailable phosphorus (P) in aquatic ecosystems. Here we establish that ecosystem nitrate and P accrual exhibits consistent and negative nonlinear correlations with organic carbon (C) availability along a hydrologic continuum from soils, through freshwaters and coastal margins, to the open ocean. Across this diversity of environments, we find evidence that resource stoichiometry (organic C:nitrate and organic C:P) strongly influences nitrate and P accumulation by regulating a suite of microbial processes which couple DOC and nutrient cycling. Collectively, these microbial processes express themselves on local to global scales by restricting the threshold ratios underlying nitrate and P accrual to a constrained stoichiometric window. Our findings help explain the fate of nitrate and P across disparate environments, which has significant implications for the management of a rapidly changing N cycle.