Oceanic dinitrification rate

Value 400 Tg N/year
Organism Biosphere
Reference L. A. Codispoti, An oceanic fixed nitrogen sink exceeding 400 TgNa-1 vs the concept of homeostasis in the fixed-nitrogen inventory, Biogeosciences, 4, 233–253, 2007
Method Measurements of the N2 produced by denitrification, a better understanding of non-canonical pathways for N2 production such as the anammox reaction, better appreciation of the multiple environments in which denitrification can occur (e.g. brine pockets in ice, within particles outside of suboxic water, etc.) suggest that it is unlikely that the oceanic denitrification rate is less than 400 TgN a^-1.
Comments Tg=Teragram=10^12 grams. Because this sink term far exceeds present estimates for nitrogen fixation, the main source for oceanic fixed-N, there is a large apparent deficit (~200 Tg N a^-1) in the oceanic fixed-N budget. The three most likely factors that could reconcile the rate of denitrification with paleo records (that are lower) are as follows: 1. Oceanic nitrogen fixation has been significantly underestimated. 2. There is a significant mis-match between the sedimentary record and ocean observations with the former largely confined to the Holocene and earlier, and the latter confined to the Anthropocene: today’s ocean may be in a transient state. 3. Century scale and shorter oscillations occur and are averaged out in the paleo record (Altabet, 2006 Gruber and Sarmiento, 1997). Note: Database - link (link-Nitrogen) gives denitrification rate of ~209Tg N/year (BNID 101681).
Entered by Uri M
ID 104774