Hagi BucknWise: Created page with "{{BreadcrumbsNutrients}} * Page authors: PRIMO * Responsible curator: Hagen Buck-Wiese ---- TOC
{| class="model-ib" style="float:right; margin-left:1em; margin-bottom:1em;" ! Nitrification rate (¹⁵N tracer) |- | '''Approach:''' ¹⁵N tracer incubation; tracking ¹⁵NO₂^- and ¹⁵NO₃^- productio..."

2026-05-12T21:12:17Z

Created page with "{{BreadcrumbsNutrients}} * Page authors: PRIMO * Responsible curator: Hagen Buck-Wiese ---- __TOC__ <div class="model-box"> {| class="model-ib" style="float:right; margin-left:1em; margin-bottom:1em;" ! Nitrification rate (15N tracer) |- | '''Approach:''' 15N tracer incubation; tracking 15NO2- and 15NO3- productio..."

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* [[Page authors|Page authors]]: [[PRIMO]]
* [[Responsible curator|Responsible curator]]: [[User:Hagi BucknWise|Hagen Buck-Wiese]]
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{| class="model-ib" style="float:right; margin-left:1em; margin-bottom:1em;"
! Nitrification rate (15N tracer)
|-
| '''Approach:''' 15N tracer incubation; tracking 15NO2- and 15NO3- production
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| '''Context:''' incubation, lab
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| '''Spatial scale:''' point sample
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| '''Temporal scale:''' hours to days
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| '''Units:''' nM d-1
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| '''Community captured:''' bulk
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| '''Co-measurements:''' ambient [NH4+], [NO2-], [NO3-]
|}
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== Method Overview ==

15N-labelled ammonium (15NH4+) and/or nitrite (15NO2-) are added to dark seawater incubations. Ammonia-oxidizing organisms convert 15NH4+ to 15NO2-, and nitrite-oxidizing organisms convert 15NO2- to 15NO3-. By tracking the appearance of 15N in the oxidized DIN pools over time (measured by IRMS after chemical conversion to N2O), the rates of ammonium oxidation and nitrite oxidation can be determined independently. Combined with dark 13C-fixation measurements in the same incubation, the chemoautotrophic production associated with nitrification can also be estimated<ref name="Ward2011">Ward, B. B. (2011). Measurement and distribution of nitrification rates in the oceans. ''Methods in Enzymology'', 486, 307–323. https://doi.org/10.1016/B978-0-12-381294-0.00013-4</ref>.

=== Scale of measurement ===

Point sample; dark incubations of hours to days. Must be performed in strict darkness to prevent phytoplankton uptake of 15N.

=== Data generated ===

Ammonium oxidation rates and nitrite oxidation rates separately (nM d-1). The ratio of ammonium to nitrite oxidation rates reveals whether the two processes are tightly coupled or spatially decoupled in the water column.

=== Units & currency ===

Units are nM d-1 (nmol N L-1 d-1). The currency is nitrogen.

=== Sample size ===

Typical samples are 250 mL to 1 L in volume.

=== Repositories & databases ===

== Limitations ==

The tracer additions must be at sufficiently low concentrations to avoid perturbing the ambient substrate pool; this is especially challenging in oligotrophic waters where ambient [NH4+] is in the low-nM range. Isotope dilution from ongoing regeneration of unlabelled NH4+ can cause underestimation. Dark incubation requirements can alter the microbial community and substrate dynamics.

== Example Applications & Protocols ==

=== Classic examples ===
* Ward (2011) ''Measurement and distribution of nitrification rates in the oceans'' <ref name="Ward2011" />

=== Recent applications ===
*

=== Common calculations/conversions ===
* Ammonium oxidation rate = d(15NO2-) / dt / atom% 15N-enrichment of NH4+ pool.
* Nitrite oxidation rate = d(15NO3-) / dt / atom% 15N-enrichment of NO2- pool.

== References ==

[[Category:Main Pages|Model types]]

15N tracers - Revision history