Size-fractionated extract spiking

2026-10-05T19:45:02Z

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* [[Page authors|Page authors]]: [[PRIMO]]
* [[Responsible curator|Responsible curator]]: [[User:Hagi BucknWise|Hagen Buck-Wiese]]
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! Allelopathy (size-fractionated extract spiking)
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| '''Approach:''' size-fractionated culture extracts added to target species; growth or Fv/Fm response measured
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| '''Context:''' lab
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| '''Spatial scale:''' culture flask (point)
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| '''Temporal scale:''' hours to days
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| '''Units:''' cells L<sup>-1</sup> d<sup>-1</sup>; Fv/Fm
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| '''Community captured:''' individual target species
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| '''Co-measurements:''' temperature, PAR; sometimes pH and salinity
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== Method Overview ==

Cell-free extracts or filtrates from a potentially allelopathic species are size-fractionated by molecular weight cutoff ultrafiltration membranes (e.g., < 1 kDa, 1–10 kDa, 10–100 kDa, > 100 kDa) or by reverse-phase solid-phase extraction (SPE) into polarity fractions. Each fraction is then added separately to cultures of a target species. The effect of each fraction on target species growth rate or photosynthetic efficiency (Fv/Fm) is quantified relative to solvent controls<ref name="Wu2010">Wu, J.-T., Chiang, Y.-R., Huang, W.-Y., & Jane, W.-N. (2010). Allelopathic control of cyanobacterial blooms by periphyton biofilms. ''Environmental Microbiology'', 13(3), 604–615. https://doi.org/10.1111/j.1462-2920.2010.02363.x</ref>. This approach identifies the molecular size range (and sometimes polarity class) of the allelopathic compound(s), aiding in their chemical characterization.

=== Scale of measurement ===

Laboratory culture; no direct ''in situ'' spatial scale. Hours to days incubation per fraction.

=== Data generated ===

Growth rate or Fv/Fm of the target species in response to each size fraction. The fraction(s) causing significant inhibition narrow down the molecular size class of the allelopathic compound.

=== Units & currency ===

Units are cells L<sup>-1</sup> d<sup>-1</sup> (growth) or Fv/Fm. The currency is cell abundance or photon relaxation.

=== Sample size ===

Typical samples are < 1 L in volume per fraction.

=== Repositories & databases ===

== Limitations ==

The size fractionation assumes that the allelopathic compound is in a specific size class and that fractionation does not alter its activity (e.g., through pH changes during ultrafiltration or solid phase extraction). Compounds may interact synergistically across fractions, making single-fraction bioassays incomplete. The assumption that a specific compound or fraction exerts the allelopathic effect must be verified by chemical identification and dose-response experiments. Longer incubations in culture flasks may introduce bottle effects, such as nutrient starvation or confinement stress, that can alter target species growth independently of the added extracts.

== Example Applications & Protocols ==

=== Classic examples ===
* Wu et al. (2010) ''Allelopathic control of cyanobacterial blooms by periphyton biofilms'' <ref name="Wu2010" />

=== Recent applications ===
*

=== Common calculations/conversions ===
* % inhibition per fraction = (Fv/Fm<sub>control</sub> − Fv/Fm<sub>fraction</sub>) / Fv/Fm<sub>control</sub> × 100; highest inhibition identifies the active size class.

== References ==

[[index.php?title=Category:Main Pages|Model types]]

OceanWiki - User contributions [en]

Size-fractionated extract spiking