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{| class="model-ib" style="float:right; margin-left:1em; margin-bottom:1em;" ! Calcification rate (¹³C) |- | '''Approach:''' stable isotope (¹³C-bicarbonate) incubation; separation of PIC and POC fractions |- | '''Context:''' incubation, lab |- | '''Spatial..."

2026-05-13T00:28:25Z

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;" ! Calcification rate (13C) |- | '''Approach:''' stable isotope (13C-bicarbonate) incubation; separation of PIC and POC fractions |- | '''Context:''' incubation, lab |- | '''Spatial..."

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* [[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;"
! Calcification rate (13C)
|-
| '''Approach:''' stable isotope (13C-bicarbonate) incubation; separation of PIC and POC fractions
|-
| '''Context:''' incubation, lab
|-
| '''Spatial scale:''' point sample; single cell
|-
| '''Temporal scale:''' hours
|-
| '''Units:''' µmol C L-1 d-1
|-
| '''Community captured:''' all (> 0.7 µm bulk); single-cell resolution available
|-
| '''Co-measurements:''' background δ13C (POC), DIC, Chl; 13C:12C of POC and PIC before and after incubation
|}
</div>
<div style="clear:both"></div>

== Method Overview ==

NaH13CO3 is added to seawater samples incubated under simulated ''in situ'' conditions. After incubation, two subsamples are collected: one filtered for total particulate material (POC + PIC), and one where carbonate is dissolved by acidification before filtration (POC only). The 13C enrichment in each fraction is measured by EA-IRMS. The difference in 13C incorporation between the total and acidified fractions reflects incorporation into particulate inorganic carbon (PIC = CaCO3), i.e., calcification rate<ref name="Slawyk1977">Slawyk, G., Collos, Y., & Auclair, J.-C. (1977). The use of the 13C and 15N isotopes for the simultaneous measurement of carbon and nitrogen turnover rates in marine phytoplankton. ''Limnology and Oceanography'', 22(5), 925–932. https://doi.org/10.4319/lo.1977.22.5.0925</ref>. This approach avoids radioactive materials and can be coupled with 15N uptake measurements in the same incubation.

=== Scale of measurement ===

Point samples after hours of incubation. At the single-cell level, nanoSIMS can measure per-cell calcification rates in individually identified coccolithophores.

=== Data generated ===

Calcification rates (µmol PIC C L-1 d-1) and organic carbon fixation rates (µmol POC C L-1 d-1), enabling direct calculation of the PIC:POC ratio (coccolithophore calcification ratio).

=== Units & currency ===

Units are µmol C L-1 d-1. The currency is carbon.

=== Sample size ===

Typical samples range from 0.3 to 4 L for bulk; nanoSIMS requires mL volumes with cells sorted or identified by FISH.

=== Repositories & databases ===

== Limitations ==

Natural variability in background δ13C of the DIC pool must be accurately measured. Isotopic changes in the DIC pool during the incubation (from CO2 invasion or outgassing) can bias rates. At the single-cell level, initial cellular carbon content must be estimated from biovolume, introducing uncertainty for cells with variable carbon densities. Bottle effects from incubation can arise.

== Example Applications & Protocols ==

=== Classic examples ===
* Slawyk et al. (1977) ''The use of the 13C and 15N isotopes for the simultaneous measurement of carbon and nitrogen turnover rates in marine phytoplankton'' <ref name="Slawyk1977" />

=== Recent applications ===
* Wu et al. (2022) ''Single-cell measurements and modelling reveal substantial organic carbon acquisition by Prochlorococcus'' <ref name="Wu2022">Wu, S., Huang, R., & Jiao, N. (2022). Single-cell measurements and modelling reveal substantial organic carbon acquisition by Prochlorococcus. ''Nature Microbiology'', 7, 2068–2077. https://doi.org/10.1038/s41564-022-01250-5</ref>
* Irion et al. (2021) ''Small phytoplankton contribute greatly to CO₂-fixation after the diatom bloom in the Southern Ocean'' <ref name="Irion2021">Irion, S., Jardillier, L., Sassenhagen, I., & Christaki, U. (2021). Small phytoplankton contribute greatly to CO₂-fixation after the diatom bloom in the Southern Ocean. ''The ISME Journal'', 15, 2509–2522. https://doi.org/10.1038/s41396-021-00915-z</ref>

=== Common calculations/conversions ===
* Calcification rate = [(13Ctotal − 13CPOC) / 13CDIC] × DIC / incubation time; where 13Ctotal and 13CPOC are the enrichments in total and acid-treated fractions respectively.

== References ==

[[Category:Main Pages|Model types]]

Calcification (13-Carbon uptake) - Revision history