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{| class="model-ib" style="float:right; margin-left:1em; margin-bottom:1em;" ! Gross oxygen production |- | '''Approach:''' stable isotope tracer (¹⁸O-water) |- | '''Context:''' incubation, ''in situ'' |- | '''Spatial scale:''' point sample |- | '''Temporal sc..."

2026-05-11T22:53:33Z

Created page with "{{BreadcrumbsPrimaryProduction}} * 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;" ! Gross oxygen production |- | '''Approach:''' stable isotope tracer (18O-water) |- | '''Context:''' incubation, ''in situ'' |- | '''Spatial scale:''' point sample |- | '''Temporal sc..."

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{{BreadcrumbsPrimaryProduction}}

* [[Page authors|Page authors]]: [[PRIMO]]
* [[Responsible curator|Responsible curator]]: [[User:Hagi BucknWise|Hagen Buck-Wiese]]
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__TOC__
<div class="model-box">
{| class="model-ib" style="float:right; margin-left:1em; margin-bottom:1em;"
! Gross oxygen production
|-
| '''Approach:''' stable isotope tracer (18O-water)
|-
| '''Context:''' incubation, ''in situ''
|-
| '''Spatial scale:''' point sample
|-
| '''Temporal scale:''' hours to one day
|-
| '''Units:''' µmol O2 L-1 d-1; convertible to µmol C L-1 d-1
|-
| '''Community captured:''' all
|-
| '''Co-measurements:''' initial dissolved O2 concentration; photosynthetic quotient (PQ) for C conversion; parallel O2/Ar measurement for respiration by difference
|}
</div>
<div style="clear:both"></div>

== Method Overview ==

H218O is added to seawater incubations, enriching the water isotopically. During oxygenic photosynthesis, phytoplankton split water molecules, releasing O2 that carries the 18O label. The accumulation of 18O2 above natural abundance is measured by isotope ratio mass spectrometry (IRMS) at the end of the incubation, and the rate of 18O2 production is converted to gross oxygen production (GOP)<ref name="Bender1987">Bender, M., Grande, K., Johnson, K., Marra, J., Williams, P. J. le B., Sieburth, J., Pilson, M., Langdon, C., Hitchcock, G., Orchardo, J., Hunt, C., Donaghay, P., & Heinemann, K. (1987). A comparison of four methods for determining planktonic community production. ''Limnology and Oceanography'', 32(5), 1085–1098. https://doi.org/10.4319/lo.1987.32.5.1085</ref>.

Unlike the 14C method, the 18O approach directly measures gross O2 production before respiratory consumption. Combined with a simultaneous measurement of net O2 exchange (e.g., via O2/Ar), community respiration can be estimated by difference.

=== Scale of measurement ===

Each incubation provides a point measurement. Standard incubations run for hours to one day. The small sample volume (~50 mL) limits the approach to discrete sampling rather than continuous deployment.

=== Data generated ===

The primary output is the gross O2 production rate. Conversion to gross carbon fixation requires the photosynthetic quotient (PQ, mol O2 produced per mol CO2 fixed, typically 1.1–1.4 depending on substrate and nitrogen source).

=== Units & currency ===

Units are µmol O2 L-1 d-1, or µmol C L-1 d-1 after PQ conversion. The primary currency is oxygen; carbon is the derived currency.

=== Sample size ===

Typical samples are ~50 mL in volume.

=== Repositories & databases ===

== Limitations ==

The method assumes that newly produced 18O2 mixes rapidly and uniformly with the dissolved O2 pool in the incubation vessel. Light-dependent O2 consumption (Mehler reaction, photorespiration) can cause overestimation of gross carbon fixation when rates are converted via PQ. Bottle confinement effects apply. Small sample volumes exclude larger, rarer phytoplankton.

== Example Applications & Protocols ==

=== Classic examples ===
* Bender et al. (1987) ''A comparison of four methods for determining planktonic community production'' <ref name="Bender1987" />

=== Recent applications ===
*

=== Common calculations/conversions ===
* GOP (µmol O2 L-1 d-1) = (18O excess in POO / 18O enrichment of water) × [O2]initial / incubation time.
* Gross C fixation = GOP / PQ.

== References ==

[[Category:Main Pages|Model types]]

18O-labelled water (GOP) - Revision history