A global marine-fixed nitrogen isotopic budget: Implications for Holocene nitrogen cycling

Nitrogen cycling in coastal marine ecosystems.

It is generally considered that nitrogen availability is one of the major factors regulating primary production in temperate coastal marine environments. Coastal regions often receive large anthropogenic inputs of nitrogen that cause eutrophication. The impact of these nitrogen additions has a profound effect in estuaries and coastal lagoons where water exchange is limited. Such increased nutri...

Isotopic constraints on the pre-industrial oceanic nitrogen budget

The size of the bioavailable (i.e., “fixed”) nitrogen inventory in the ocean influences global marine productivity and the biological carbon pump. Despite its importance, the pre-industrial rates for the major source and sink terms of the oceanic fixed nitrogen budget, N2 fixation and denitrification, respectively, are not well known. These processes leave distinguishable imprints on the ratio ...

Global Nitrogen: Cycling out of Control

Nitrogen cycling in deeply oxygenated sediments: Results in Lake Superior and implications for marine sediments

To understand the nitrogen (N) cycle in sediments with deep oxygen penetration, we measured pore-water profiles to calculate N fluxes and rates at 13 locations in Lake Superior in water depths ranging from 26 to 318 m. Sediments with high oxygen demand, such as in nearshore or high-sedimentation areas, contribute disproportionally to benthic N removal, despite covering only a small portion of t...

Nitrogen cycling and feedbacks in a global dynamic land model

Global anthropogenic changes in carbon (C) and nitrogen (N) cycles call for modeling tools that are able to address and quantify essential interactions between N, C, and climate in terrestrial ecosystems. Here, we introduce a prognostic N cycle within the Princeton-GFDL LM3V land model. The model captures mechanisms essential for N cycling and their feedbacks on C cycling: N limitation of plant...