Compute primary production based on single cell C14 uptake

2 min read phytoplankton

Classical formula for filtered samples

The classical formula can be found here or here

Pvol=DIC⋅DPMvolDPMadded⋅1.05⋅1000

and plugging the value for DPMadded (see below):

Pvol=DIC⋅DPMvolSA⋅V⋅1.05⋅1000

where:

  • Pvol = Primary Productivity per unit volume in mgC⋅m−3⋅d−1

  • DIC = Dissolved inorganic carbon in mgC⋅L−1

  • DPMvol = DPM measured during 24 h for volume V (filtered)

  • DPMadded = SA⋅V

  • SA = Standard activity in 1 mL (DPM per mL)

  • V = Volume of incubation (mL)

  • 1.05 is to account for differential uptake between 14C and 12C

  • 1000 is to go from from L−1 to m−3 since DIC is in mgC⋅L−1

For cells sorted by flow cytometry

Let us define:

  • DPMcells = DPM measured during 24 h for N cells

  • N = number of cells sorted

  • C = cell concentration per mL

  • Pcell = Primary productivity per cell (fgC⋅cell−1⋅h−1)

Pcell can be computed from Pvol by dividing it by the total number of cells in 1 m−3:

Pcell=Pvol⋅1C⋅106⋅124⋅1012

  • 1012 is to convert from milligrams to femtograms

  • 24 is to convert from day to hours

  • C⋅106 is the number of cells per m−3

Which simplifies to:

Pcell=Pvol⋅1C⋅124⋅106

We now replace Pvol by the formula provived at the top :

Pcell=DIC⋅DPMvolSA⋅V⋅1.05⋅1000⋅1C⋅124⋅106

Simplifies to :

Pcell=DIC⋅DPMvolSA⋅V⋅C⋅1.05⋅124⋅109

DPMvol can be computed from the individual DPM per cell (DPMcells/N) as:

DPMvol=DPMcells⋅C⋅VN

So that:

Pcell=DIC⋅DPMcells⋅C⋅VSA⋅V⋅C⋅N⋅1.05⋅124⋅109

which simplifies finally to:

Pcell=DIC⋅DPMcellsSA⋅N⋅24⋅1.05⋅109

With contributions from Adriana Lopes dos Santos (ASE, NTU) and Andres Gutierrez-Rodriguez (NIWA)

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