View source for 15N/13C-labelled DOM/cells

{{BreadcrumbsInteractions}}

* [[Page authors|Page authors]]: [[PRIMO]]
* [[Responsible curator|Responsible curator]]:  [[User:Hagi BucknWise|Hagen Buck-Wiese]]
----

__TOC__
<div class="model-box">
{| class="model-ib" style="float:right; margin-left:1em; margin-bottom:1em;"
! Osmotrophic mixotrophy (<sup>13</sup>C/<sup>15</sup>N DOM assimilation)
|-
| '''Approach:''' <sup>13</sup>C/<sup>15</sup>N-labelled dissolved or particulate organic matter; EA-IRMS or nanoSIMS
|-
| '''Context:''' incubation, lab
|-
| '''Spatial scale:''' single cell to community
|-
| '''Temporal scale:''' 24 h
|-
| '''Units:''' µmol C or N L<sup>-1</sup> d<sup>-1</sup>; fmol cell<sup>-1</sup> d<sup>-1</sup> (nanoSIMS)
|-
| '''Community captured:''' osmotrophic mixotrophs (e.g., specific flagellate species or picophytoplankton)
|-
| '''Co-measurements:''' temperature, PAR, bulk POC and PON, cell abundance
|}
</div>
<div style="clear:both"></div>

== Method Overview ==

<sup>13</sup>C- and <sup>15</sup>N-labelled dissolved organic matter (DOM) or particulate organic cells are added to incubation bottles containing natural seawater communities. Osmotrophic mixotrophs — organisms capable of both photosynthesis and uptake of dissolved or particulate organic compounds — incorporate the labelled substrates into their biomass. After incubation, the bulk <sup>13</sup>C and <sup>15</sup>N enrichment of the particulate fraction is measured by EA-IRMS, providing community-level assimilation rates. For single-cell resolution, cells are fixed, filtered, and analysed by nanoSIMS, revealing which individual cells (identified by FISH or flow cytometry) assimilated the labelled substrate and at what per-cell rate<ref name="Millette2023">Millette, N. C., Leles, S. G., Johnson, M. D., & Menden-Deuer, S. (2023). Mixoplankton and mixotrophy: future research priorities. ''Journal of Plankton Research'', 45(4), 576–596. https://doi.org/10.1093/plankt/fbad020</ref>.

=== Scale of measurement ===

Discrete samples are collected and incubated for 24 h. NanoSIMS provides single-cell resolution with ~50 nm spatial precision.

=== Data generated ===

Community-level DOM assimilation rates (µmol C or N L<sup>-1</sup> d<sup>-1</sup>) from EA-IRMS, or per-cell assimilation rates (fmol C or N cell<sup>-1</sup> d<sup>-1</sup>) from nanoSIMS. Identifies which populations in the community are actively assimilating organic substrates.

=== Units & currency ===

Units are µmol C or N L<sup>-1</sup> d<sup>-1</sup> (bulk) or fmol cell<sup>-1</sup> d<sup>-1</sup> (single cell). The currency is carbon and/or nitrogen.

=== Sample size ===

Typical samples are > 1 L in volume for bulk EA-IRMS; mL for nanoSIMS.

=== Repositories & databases ===

== Limitations ==

There is a trade-off between incubation time (needed for detectable <sup>13</sup>C/<sup>15</sup>N enrichment) and confidence that the label has not cycled through multiple steps (e.g., DOM mineralized and re-fixed by autotrophs). Bottle effects apply. For nanoSIMS, the low throughput (tens to hundreds of cells per session) limits statistical power.

== Example Applications & Protocols ==

=== Classic examples ===
*

=== Recent applications ===
* Millette et al. (2023) ''Mixoplankton and mixotrophy: future research priorities'' <ref name="Millette2023" />

=== Common calculations/conversions ===
* Per-cell assimilation rate (nanoSIMS) = [(<sup>13</sup>C/<sup>12</sup>C)<sub>cell</sub> − (<sup>13</sup>C/<sup>12</sup>C)<sub>natural</sub>] / [(<sup>13</sup>C/<sup>12</sup>C)<sub>DOM</sub> − (<sup>13</sup>C/<sup>12</sup>C)<sub>natural</sub>] × C<sub>cell</sub> / incubation time.

== References ==

[[Category:Main Pages|Model types]]