How are ecological dynamics and carbon cycling affected by the basin scale differences between nitrogen fixation and denitrification?
Nitrogen fixation creates reactive nitrogen which is then available to the rest of the life in the sea. Denitrification removes this reactive nitrogen as part of the metabolism of a specific group of micro-organisms. The balance of these two processes controls the total pool of reactive nitrogen, primarily nitrate, in the ocean. The Pacific Ocean contains one of the largest areas of water column and sediment denitrification in the world. Nitrogen fixation is widespread over the oligotrophic surface waters of the Pacific and apparently fluctuates on interannual and decadal time-scales, although the absolute rates over the whole basin are unclear. The creation of reactive nitrogen by diazotrophs will result in the net uptake of atmospheric CO2, and denitrification will cause the return of CO2 to the atmosphere, modulated by the residence time of the nitrate in the ocean. If these two rates are exactly in balance, the net exchange of CO2 with the atmosphere will be zero; imbalances betwee
