Methodological Underestimation of Oceanic Nitrogen Fixation Rates

Methodological Underestimation of Oceanic Nitrogen Fixation Rates

The two commonly applied methods to assess dinitrogen (N(2)) fixation rates are the (15)N(2)-tracer addition and the acetylene reduction assay (ARA). Discrepancies between the two methods as well as inconsistencies between N(2) fixation rates and biomass/growth rates in culture experiments have been attributed to variable excretion of recently fixed N(2). Here we demonstrate that the (15)N(2)-t...

Extensive hydrogen supersaturations in the western South Atlantic Ocean suggest substantial underestimation of nitrogen fixation

The nitrogen cycle is fundamental to Earth’s biogeochemistry. Yet major uncertainties of quantification remain, particularly regarding the global oceanic nitrogen fixation rate. Hydrogen is produced during nitrogen fixation and will become supersaturated in surface waters if there is net release from diazotrophs. Ocean surveys of hydrogen supersaturation thus have the potential to illustrate th...

Magnitude of oceanic nitrogen fixation influenced by the nutrient uptake ratio of phytoplankton

The elemental stoichiometry of sea water and particulate organic matter is remarkably similar. This observation led Redfield to hypothesize that the oceanic ratio of nitrate to phosphate is controlled by the remineralization of phytoplankton biomass1. The Redfield ratio is used universally to quantitatively link the marine nitrogen and phosphorus cycles in numerous biogeochemical applications2–...

Deep Into Oceanic N2 Fixation

Nitrogen Fixation

Plant growth is directly dependent upon an adequate supply of fixed nitrogen. Water and fixed nitrogen are the most common limiting factors for plant growth.There is an abundance of nitrogen in the atmosphere, but it is in the form of the relatively inert gas, N2, and this must be converted chemically or biologically into a more active form before plants can utilize it. Chemical fixation most c...