View source for Size-fractionated incubation dilution experiments

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* [[Page authors|Page authors]]: [[PRIMO]]
* [[Responsible curator|Responsible curator]]:  [[User:Hagi BucknWise|Hagen Buck-Wiese]]
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! Microzooplankton grazing, size-fractionated
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| '''Approach:''' dilution method with FCM or HPLC tracking of size-class phytoplankton
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| '''Context:''' incubation
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| '''Spatial scale:''' point sample
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| '''Temporal scale:''' hours (one diel cycle)
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| '''Units:''' d<sup>-1</sup>
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| '''Community captured:''' size-fractionated phytoplankton (FCM populations or HPLC pigment groups)
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| '''Co-measurements:''' temperature, simulated or ''in situ'' PAR, depth of collection
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== Method Overview ==

This is the size-fractionated variant of the [[Incubation dilution experiments]] method, in which phytoplankton growth and grazing rates are resolved for distinct size classes or taxonomic groups rather than the bulk community. The dilution procedure is identical to the standard method: whole seawater is diluted with particle-free (0.2 µm) filtrate across a dilution series. Rather than tracking bulk chlorophyll-a, phytoplankton biomass in distinct populations is measured by flow cytometry (resolving Prochlorococcus, Synechococcus, picoeukaryotes, nanoeukaryotes) or by HPLC pigment analysis<ref name="Morison2017">Morison, F., & Menden-Deuer, S. (2017). Doing more with less? Balancing sampling resolution and effort in measurements of protistan growth and grazing rates. ''Limnology and Oceanography: Methods'', 15, 794–809. https://doi.org/10.1002/lom3.10200</ref>. Separate µ and g values are derived for each resolvable population, revealing which phytoplankton groups are most heavily grazed.

=== Scale of measurement ===

Point sample; 24 h incubation. Multiple populations resolved within a single dilution series provide a more complete picture of community trophic dynamics than bulk Chl tracking alone.

=== Data generated ===

Population-specific phytoplankton growth rates (µ, d<sup>-1</sup>) and microzooplankton grazing rates (g, d<sup>-1</sup>) for each FCM-resolvable population or HPLC-derived taxon group.

=== Units & currency ===

Units are d<sup>-1</sup>. The currency is Chl-a or cell counts.

=== Sample size ===

Typical samples are 1–2 L per dilution treatment.

=== Repositories & databases ===

== Limitations ==

Same assumptions apply as for the bulk dilution method. FCM populations must be optically distinct; overlapping populations cannot be separated. HPLC pigment markers require taxon-specific pigment:Chl ratios for biomass conversion.

== Example Applications & Protocols ==

=== Classic examples ===
* Morison & Menden-Deuer (2017) ''Doing more with less? Balancing sampling resolution and effort in measurements of protistan growth and grazing rates'' <ref name="Morison2017" />

=== Recent applications ===
* Marrec & Menden-Deuer (2024) ''Changes in phytoplankton size-structure alter trophic transfer in a temperate, coastal planktonic food web'' <ref name="Marrec2024">Marrec, P., & Menden-Deuer, S. (2024). Changes in phytoplankton size-structure alter trophic transfer in a temperate, coastal planktonic food web. ''Limnology and Oceanography Letters'', 9(5), 624–633. https://doi.org/10.1002/lol2.10410</ref>

=== Common calculations/conversions ===
* As for the bulk dilution method, applied separately to each FCM population or pigment group.

== References ==

[[Category:Main Pages|Model types]]