BACKGROUND Biological dinitrogen (N2) fixation, the reduction of atmospheric N2 to
ammonia, is important for maintaining the fertility of the oceans by providing biologically …

Global nitrogen fixation contributes 413 Tg of reactive nitrogen (Nr) to terrestrial and marine
ecosystems annually of which anthropogenic activities are responsible for half, 210 Tg N …

Cyanobacteria are the Earth's oldest (∼ 3.5 bya) oxygen evolving organisms, and they have
had major impacts on shaping our modern-day biosphere. Conversely, biospheric …

In many aquatic systems, N2 fixation is an important component of the nitrogen (N) cycle.
Nitrogenase is a molybdenumenzyme complex found in phylogenetically diverse …

The oceans take up over 1 million tons of anthropogenic CO2 per hour, increasing dissolved
p CO2 and decreasing seawater pH in a process called ocean acidification (OA). At the …

This paper contrasts the natural and anthropogenic controls on the conversion of unreactive
N 2 to more reactive forms of nitrogen (Nr). A variety of data sets are used to construct global …

For the past 3.8 billion years, the geochemistry of the Earth's surface-its atmosphere, waters
and exposed crust-has been determined by the presence of biota. Photosynthetic organisms …

The stable nitrogen and carbon isotope ratios of bone collagen prepared from more than
100 animals representing 66 species of birds, fish, and mammals are presented. The δ 15 N …

The decline of dissolved oxygen in the oceans could be detrimental to marine life and
biogeochemical cycles. However, predicting future oxygen availability with models that …

The way that nutrients cycle through atmospheric, terrestrial, oceanic and associated biotic
reservoirs can constrain rates of biological production and help structure ecosystems on …