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Red and blue light cues drive contrasting remodeling of lipophilic metabolites and photophysiology in natural benthic diatom biofilms

Alexandre DesparmetiD, Johann LavaudiD, Bruno JesusiD, Antoine Medico, Cédric HubasiD

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In-depth summary

Claude Opus 5.5 · xhigh effort · 7 Nov 2026 · from the full text of version 2 (12 Oct 2026) · CC BY 4.0

Within 30 minutes, red light remodeled natural benthic diatom lipids and pigments more than blue; blue high light most altered photophysiology; de-epoxidation was similar at equal incident intensity.

Benthic diatoms on intertidal mudflats face fast shifts in light colour and intensity, and the authors note that metabolic responses have seldom been studied at the scale of natural communities. Here a field-collected diatom assemblage is exposed to red or blue light at two intensities, with untargeted lipids, lipophilic pigments and photosystem II fluorescence measured together.

Key results

  1. ShownLight treatment significantly restructured the combined lipid and pigment profiles within 30 minutes. Red light moved samples further from their dark-adapted controls than blue light did.

    PERMANOVA on all MFA dimensions gave R^2 = 0.404, p = 0.001 (133 metabolites: 35 pigments, 98 lipids). Centroid Euclidean distances in MFA space were largest between the red treatments and their controls. Separate lipid and pigment PCAs agreed, with lipids most differentiated under red low light. The contrast between low and high intensity was larger under blue light. · Light-driven and temporal remodeling of pigments…; Data treatment

  2. ShownOnly blue high light strongly changed photosystem II photophysiology; the other three treatments caused small shifts.

    Relative to dark-adapted controls (Welch's t-test, n = 3), blue high light gave Y(NO)m obs +43.0%, α-slope −47.0%, Fv/Fm −50.3% and Y(NPQ)^1000 −42.5%. Red high light slightly raised Y(NO)m obs and blue low light raised rETRm obs (p < 0.05). Before treatment, Fv/Fm was 0.48 to 0.55 and α-slope 0.25 to 0.29. · Xanthophyll-cycle and photophysiological…; Chlorophyll fluorescence: Pulse amplitude…; Data treatment

  3. ShownThe xanthophyll cycle tracked intensity more than colour. De-epoxidation rose with light under both spectra and at the same incident intensity was slightly higher, but comparable, under red light.

    Under both spectra, diatoxanthin rose and diadinoxanthin fell along the intensity gradient (Van der Waerden test, p < 0.05; n = 5). The de-epoxidation state reached maxima of 14.9% (red) and 13.1% (blue), up from control values of 3% (red) and 2.6% (blue). · Xanthophyll-cycle and photophysiological…; Contrasting light spectra, comparable…

  4. SuggestedPolyunsaturated fatty acids and β-carotenes declined along the red intensity gradient but rose under blue low light, while alkanes moved the opposite way. Few metabolites changed with time of day alone.

    Significant metabolites (Van der Waerden test): C16:4, C18:2 ω6, C18:4 ω3 and C20:4 ω3 (p < 0.05). Alkanes fell under blue low light (p = 0.046). Monounsaturated fatty acids differed only between the red and blue dark controls (p = 0.007). Of the 66 top-loading metabolites, 23 were light-responsive, 4 and 8 were time-affected and 31 were stable. · Light-driven and temporal remodeling of pigments…; Rapid lipophilic metabolite remodeling in…

  5. SuggestedEstimates of absorbed rather than incident light indicate that blue light delivered much more energy, so red light gave a steeper de-epoxidation response relative to the light absorbed. The authors treat these estimates as indicative only.

    Package-corrected estimates of photosynthetically usable light (Qphar) indicate about 4.2-fold more blue than red light was absorbed. Blue high light energy input was 3.9-fold that of blue low light, 6.1-fold red high light and 22.3-fold red low light. De-epoxidation slopes against absorbed photons and energy were markedly higher under red light. · Xanthophyll-cycle and photophysiological…; Contrasting light spectra, comparable…; An underperforming blue light response or a…

Methods, data and reproducibility

Motile diatoms recovered from a natural winter biofilm were exposed in suspension for 30 min to red (peak 640 nm) or blue (peak 450 nm) LED light at 200 or 800 µmol photons m^-2 s^-1, with dark-adapted controls. Pigments (HPLC) and untargeted lipids (GC-MS) were analysed by multiple factor analysis, PERMANOVA and Van der Waerden tests; fluorescence light curves by Welch t-tests.

  • Natural winter microphytobenthic biofilm (upper centimetre of sediment) from a tidal outdoor pond at Concarneau Marine Station, France, collected 13 January 2025 · motile diatom assemblage (Bacillariophyceae)
  • Diatom suspension dishes for HPLC pigment and GC-MS lipid profiling: red and blue dark-adapted controls plus low and high light treatments · diatoms, dominated by Pleurosigma strigosum (63.3%) · n = 5 dishes per treatment; after exclusions, 3 to 5 per group in the MFA
  • Diatom suspension dishes for chlorophyll fluorescence rapid light curves, measured before and after treatment · diatoms, dominated by Pleurosigma strigosum · n = n = 3 per treatment
Methods & tools
MonitoringPen MP 100-E fluorometer (Photon System Instruments), LED panels SN-SL3500-342 (Photon Systems Instruments), MSC15 radiometer with S-MSC15 software (Gigahertz-Optik), Agilent 1260 Infinity HPLC (Supelcosil C18 column, DAD 1260 VL detector), Agilent 7890B GC with 5977B MSD (HP-5ms Ultra Inert column), ProteoWizard MSconvertGUI, eRah (R package), NIST 2017 MS Search, InChI Library, ClassyFire, Sedgewick-Rafter chamber
Reagents & environment
ProteoWizard MSconvertGUI v3.0.24100; R package eRah v2.0.1 with its deconvolution and alignment parameters listed; NIST 2017 MS Search v2.3 with InChI Library v1.05; S-MSC15 software v2018.2.1.
Reproducibility gaps
No code or data links are printed. Raw chromatograms, metabolite tables and statistical scripts have no stated repository, and the statistical software beyond eRah is not named.
Limitations (6)
  • Conditions departed from those in situ: the sediment was removed, which limits vertical migration, and the light was monochromatic. Photoacclimation also depends on species and context, so ecological interpretation needs care. · stated by the authors
  • The absorbed-light estimates (Qphar, Pabs, Eabs) do not account for karyostrophy (chloroplast contraction). They are probably overestimated, especially under blue high light, and should be read as indicative. · stated by the authors
  • Karyostrophy may distort fluorescence signals, so the rise in Y(NO) and the loss of Y(NPQ) under high light cannot be cleanly attributed to photoinhibition. · stated by the authors
  • The alkanes may come from diatoms or from associated phycosphere bacteria. Some red light lipid samples were excluded because their chromatograms were unusable, and the underlying mechanisms remain unresolved. · stated by the authors
  • Red treatments ran in the morning and blue treatments in the afternoon of one day, so spectrum is partly confounded with time of day. Separate dark controls for each spectrum only partly offset this; those controls differed in monounsaturated fatty acids and F0. · noted in this summary
  • The data come from a single biofilm collection with 3 to 5 dishes per group. Many metabolite-level Van der Waerden tests were run, and no multiple-testing correction is described. · noted in this summary

Read this if you study diatom or microphytobenthos photoacclimation and want paired lipid, pigment and fluorescence data on how light colour and intensity act within 30 minutes in a natural assemblage.

Citations
1

Abstract

Intertidal mudflats are low hydrodynamic energy environments hosting microphytobenthic communities that experience strong spatiotemporal variability in light regimes, including changes in spectral quality and light intensity that can lead to cellular photooxidative stress. To cope with these fluctuations, autotrophs exhibit diverse and highly plastic adaptations that are often species-dependent and shaped by their ecological niches. This study investigates photophysiological responses and metabolic remodeling in a diatom assemblage originating from a natural winter microphytobenthic biofilm under contrasting red and blue light intensities. To this end, photosynthetic parameters were monitored alongside changes in lipophilic metabolites, including untargeted lipids and lipophilic pigments. While few metabolites showed temporal remodeling, rapid and contrasting changes were observed within 30 minutes in response to both spectral quality and light intensity. Red light treatments induced broader remodeling of lipophilic metabolites than blue light, whereas blue light appeared to have a greater impact on photosynthetic parameters. Moreover, red light induced xanthophyll-cycle responses comparable to those observed under blue light at equivalent incident intensity. We discuss these metabolic responses in relation to diatom photoadaptive strategies, placing these findings within the intertidal environmental framework. This work further underlines the importance of understanding rapid metabolic plasticity in coping with light fluctuations, providing new insights into the photoregulatory strategies of natural microphytobenthic communities.

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