The sensitivity of marine N2 fixation to dissolved inorganic nitrogen

The sensitivity of marine N2 fixation to dissolved inorganic nitrogen

The dominant process adding nitrogen (N) to the ocean, di-nitrogen (N(2)) fixation, is mediated by prokaryotes (diazotrophs) sensitive to a variety of environmental factors. In particular, it is often assumed that consequential rates of marine N(2) fixation do not occur where concentrations of nitrate (NO(-) (3)) and/or ammonium (NH(+) (4)) exceed 1μM because of the additional energetic cost as...

On the influence of “non-Redfield” dissolved organic nutrient dynamics on the spatial distribution of N2 fixation and the size of the marine fixed nitrogen inventory

Dissolved organic nitrogen (DON) and phosphorus (DOP) represent themost abundant formof their respective nutrient pool in the surface layer of the oligotrophic oceans and play an important role in nutrient cycling and productivity. Since DOP is generally more labile than DON, it provides additional P that may stimulate growth of nitrogen-fixing diazotrophs that supply fixed nitrogen to balance ...

Nitrogen Fixation Among Marine Bacterioplankton

Major bacterial contribution to marine dissolved organic nitrogen

Next to N2 gas, the largest pool of reduced nitrogen in the ocean resides in the enormous reservoir of dissolved organic nitrogen (DON). The chemical identity of most of this material, and the mechanisms by which it is cycled, remain fundamental questions in contemporary oceanography. Amino acid enantiomeric ratios in the high molecular weight fraction of DON from surface and deep water in thre...

Cyanobacterial N2 fixation in presence of nitrogen fertilizers.

Anabaena oryzae ARM 570 was examined for its growth (chlorophyll and protein), heterocyst frequency, nitrogenase (acetylene reduction) activity, ammonia excretion, and glutamine synthetase and nitrate reductase in response to two levels of urea-N vis-à-vis N2-N. Growth of cyanobacterium increased with duration of incubation. Reduction in heterocyst frequency (40%) was observed at 30 ppm of urea...