Red or Blue pill? Light sensitive diatoms may hold key to a big portion of the climate puzzle

From the Helmholtz Centre for Environmental Research: In between red light and blue light: Leipzig researchers discover new functionality of molecular light switches

Diatoms play an important role in water quality and in the global climate. They generate about one fourth of the oxygen in the Earth’s atmosphere and perform around one-quarter of the global CO2 assimilation, i.e. they convert carbon dioxide into organic substances. Their light receptors are a crucial factor in this process. Researchers at the Leipzig University and the Helmholtz Centre for Environmental Research have now discovered that blue and red light sensing photoreceptors control the carbon flow in these algae. These results have been recently published by the scientists in the well-known online trade journal, PLOS ONE.

Microscopical picture of a diatom(<i>Phaeodactylum-tricornutum</i>), Source: Leipzig Univerity

Microscopical picture of a diatom (Phaeodactylum-tricornutum), Source: Leipzig Univerity

“Diatoms display a special way of reacting to light and adapting their metabolism to the changing light conditions in the water”, says Prof. Dr. Christian Wilhelm, Head of the Plant Physiology Department at the Leipzig University. “For the first time, we have been able to show that the light receptors, which measure the intensity of the blue or red light, not only change the genetic transcription, but also directly control the activity of enzymes in the metabolism.”

A rapid light change from blue light to red light and vice versa does not influence the photosynthesis output, but the metabolism is drastically reversed within 15 minutes. “This way, cells that have grown in red light, which continue to be cultivated in a blue light environment can still perform photosynthesis, but can no longer grow.” These “light switches” can be used to control the carbon flow in cells. The evidence for this was provided using the MetaPro metabolomic platform established at the Helmholtz Centre for Environmental Research. “This opens up new ways for the biotechnological control of cells”, explains Christian Wilhelm.

“This work is further evidence of the added-value of intensive cooperations between non-university and university institutions, particularly with the Faculty of Biosciences, Pharmacy and Psychology”, Prof. Martin von Bergen, Spokesman of the Department of Metabolomics at the UFZ and one of the co-authors, is pleased to say.

The Leipzig-based algae experts in plant physiology at the Leipzig University already drew attention to itself two years ago with another publication: Together with scientists from Karlsruhe and Bremen, they provided evidence that sunlight can be converted into pure natural gas in a highly efficient manner with the aid of microorganisms. In doing so, the metabolism of green algae is reversed.

The publication about the diatoms:

DOI: 10.1371/journal.pone.0099727

The Acclimation of Phaeodactylum tricornutum to Blue and Red Light Does Not Influence the Photosynthetic Light Reaction but Strongly Disturbs the Carbon Allocation Pattern

The publication about the green algae:

DOI: 10.1016/j.biortech.2012.06.120

Methane production from glycolate excreting algae as a new concept in the production of biofuels


I’ve often wondered about biologically based global albedo feedbacks in the ocean related to changes the solar output. What changes in TSI makeups occur and what affect does it have on the trillions of small animals like diatoms in the ocean? What about ultraviolet, which seems to have larger swings than TSI?

These are important questions to me. If anyone has some citations to add that will help fill int he gaps, please post them in comments – Anthony


44 thoughts on “Red or Blue pill? Light sensitive diatoms may hold key to a big portion of the climate puzzle

  1. Diatoms are algal phytoplankton, not animals. The effect of TSI of course is less important than the specific wavelengths photosynthesizers use, ie parts of the visible spectrum, which fluctuates less than UV.

    • I read the above through carefully; twice. I didn’t find anywhere where it said exactly what the blue or red light (and I presume they mean radiation) actually does, Well they say they control the carbon flow. Well great, so does the pump at my gas station.
      What exactly is it, that the red light controls, and same for the blue light ??
      “””…“This work is further evidence of the added-value of intensive cooperations between non-university and university institutions, particularly with the Faculty of Biosciences, Pharmacy and Psychology”, Prof. Martin von Bergen, Spokesman of the Department of Metabolomics at the UFZ and one of the co-authors, is pleased to say…..””””
      What is he saying ??
      Yes it’s an interesting critter, but is that one of them, or four of them ? I’ve seen plenty of blue flashing phytoplankton; never ever seen red flashing ones.

      • From the paper:
        “Accordingly, blue light (BL) can be defined as the spectral range with a center wavelength of approximately 460 nm and red light (RL) with a center wavelength of about 660 nm.”
        As you may know, visible light runs from about 400 to 700 nm.
        From ICL Astrophysics site:
        The total solar irradiance (TSI) is measured to be approximately 1366 Wm^-2. The spectral solar irradiance (SSI) is the incident radiation observed with a particular wavelength, measured in units of Wm^-3 or Wm^-2nm^-1.
        The SSI is important because different parts of the solar spectrum affect different regions of Earth’s atmosphere (see Figure 2). Most of the solar energy is emitted in the visible (40% of TSI emanates in the 400-700 nm region), but because parts of the solar spectrum are produced from different regions in the solar atmosphere they can vary independently of each other. As a result the ultraviolet (below 400 nm) contributes ~60% of the total variability in TSI.

      • Color Frequency Wavelength
        violet 668–789 THz 380–450 nm
        blue 606–668 THz 450–495 nm
        green 526–606 THz 495–570 nm
        yellow 508–526 THz 570–590 nm
        orange 484–508 THz 590–620 nm
        red.. 400–484 THz 620–750 nm

      • The 1931 CIE standard Photopic Luminosity Function (standard human eyeball) lists the recommended values for y-bar from 380 nm (0.0000) out to 775 nm (0.0000) The first and last non zero values to 4 decimal places are at 385 nm, and 760 nm. Both at the value 0.0001.
        Note that the photopic luminosity function applies for ordinary light levels.
        The Scotopic luminosity function for the dark adapted eye, can detect much lower levels.
        They give 0.00059 at 380 nm, and 0.000,000,139 at 780 nm.
        From The Science of Color.” published by The Commission on Colorimetry of The Optical Society of America.
        So I already know what blue light and red light are.
        I asked what they do specifically to these phytoplanktonites.

      • The human eye does all kinds of strange things color wise. This is most apparent for the yellow hue.
        In general, when luminance is changed, the hue will not stay the same. But there are four monochromatic wavelengths for which the hue does remain constant, over a retinal luminance range of 1o to 2,000 Trolands. Those wavelengths are 474, 494, 506, and 571 nm. This is called the Bezold-Brucke effect. German readers need an umlaut over the u.
        Also four wavelengths seem to the eye to be very simple hues. They are 476 and 575 nm, and 521 and 494. They form complementary pairs.
        The sensitivity to desaturation, is most acute for the yellow at about 575 nm. The eye can only perceive about five distinguishable levels of desaturation from the monochromatic 575 nm, and the white point (Source C).
        The blue yellow pair at 448, and 568.7 nm produce white light at the highest luminous efficacy of 400 lumens per watt.
        Modern white LEDs, have just recently achieved 200 lumens per watt. The above blue yellow pair has quite poor CRI (color rendition index). A fancy way to say, it makes a great white flashlight, but is very poor for showing off your expensive yuppie merchandise.
        (NO red).
        The eye only sees yellow over about 5 nm. Longer wavelength looks gold, and shorter looks grellow (ersatz green).
        A nitrogen doped yellow GaAsP LED, may look a tad greenish when you probe it on the wafer, and yellow when you die attach, and wire bond a single die, but it will look gold when you encapsulate it in an epoxy lens.
        Dunno, whether these sea monsters like yellow or not.

    • Michael, Mike.
      I hope you are both right.
      Perhaps – probably – you are.
      As a simple sailor, I am out of my depth with: –
      ” The evidence for this was provided using the MetaPro metabolomic platform established at the Helmholtz Centre for Environmental Research.”
      I expect that this is a new sort of thingy [technical term] that proper scientists can use.
      But ‘metabolomic platform’ – MetaPro or otherwise – could do with a simple black-box explanation for souls like me lacking a recent PhD with honours, lapels, Smarties and desert boots, in – uhh, say – metabolomics.
      I think, anyway.
      Note – per the Fountain of All Truth [TM] [/Sarc (might you have guessed)] – Wikipedia: –
      “Metabolomics is the scientific study of chemical processes involving metabolites. Specifically, metabolomics is the “systematic study of the unique chemical fingerprints that specific cellular processes leave behind”, the study of their small-molecule metabolite profiles.”
      – downloaded at 2021 Z 21 October 2014.
      And I fear this doesn’t leave me (a Bum-Boatie) very much the wiser.

      • Clue: check out the root when the compound confuses. Metabolite: Any substance involved in metabolism (either as a product of metabolism or as necessary for metabolism)

        • The correct definition of metabolite is something that is produced or consumed in a metabolic reaction. Depending on what your focus is, the reaction can be a single-step reaction or a chain of multiple reactions called a pathway. Metabolites involved in a pathway are often called intermediates (to distinguish them from the initial substrate and the final product of a pathway).
          Things that are necessary for metabolism are not in this category. They have special names: enzymes, co-enzymes and cofactors.
          Metabolomics is an attempt to account for all compounds involved in the metabolism of a single organism or a community. Its success is limited because all of its methods are based on mass separation. I cannot set apart different compounds having the same molecular mass.

    • In many ways, the research is associated with biotechnology rather than climate change. They are looking at different patterns of gene expression responses to blue light and red light, despite the fact that photosynthesis occurs with both. It appears that the phytoplankton have two alternative sets of genetic pathways leading to cell growth, one in response to red light and one in response to blue. Presumably there must be some kind of advantage in having both systems?
      It also sounds as if they are looking at long term use of algae to generate gas for energy. It’s a common form of research right now, like ExxonMobil researching microorganisms which can produce oil. Basically it is humans looking to drive in controlled ways the natural energy generation processes that nature has already provided, albeit to timetables considerably more rapid than nature traditionally used.

  2. They define blue light based on a center wavelength. Don’t know if their light source was leaking much UV.

  3. Assume the evolutionary origin of this trick is survival in different depths in the water column (blue and red ends of the spectrum being very differently absorbed in water). And, yes, there are a lot of them, and a lot of different species, but what is the proposed link to the climate numbers? i’m not following…

    • mothcatcher said: “blue and red ends of the spectrum being very differently absorbed in water”
      Could be an important point – from diving in the tropics, one observes there is very little visible colour (except blue) present below a few metres of ocean depth.

    • So river estuaries feed into fertile areas for diatoms? That seems plausible to me.
      The use of phosphate fertilisers changing the climate also seems plausible to me.
      And, because of the Green revolution and changing agricultural practices in the 20thC, it may be testable.

      • Latitude: If there is iron in African dust, it will can cause green bloom where iron is limiting while nutrients are abound (multiple clades including bacteria and euks, highly diverse). Iron is the tool bit in chlorophyll and in many enzymes.
        Red tides are things like Gonyaulax, whose bloom is associated with deep-sea upwelling. Gonyaulax is also known for its luminescence (both blue and red).

  4. Good primer is to start here:
    A much more detailed document from the Journal of Phycology:
    Gustaaf M. Hallegraeff
    online resource at:
    (paywalled, 0.9 Mb pdf)
    Here is a sample Figure from the Hallegraeff Review:
    Some historical data from the 1982-83 El Nino:
    Satellite Color Observations of the Phytoplankton Distribution in the Eastern Equatorial Pacific During the 1982-1983 El Niño. GENE FELDMAN, DENNIS CLARK, DAVID HALPERN
    online resource at:
    (paywalled, 1.1 Mb pdf)
    Figure 2 from Feldman, Clark, Halpern.
    If anyone would like the above docs as a pdf, email me at:
    joel(dot)obryan(at)gmail(dot)com ,
    and I will reply with pdf doc

    • Some excerpts from the Hallegraeff Review:
      “Models have estimated that a 50%
      decrease in oceanic calcification from ocean acidification
      thus would reduce atmospheric CO2 by
      10–40 ppm (Heinze 2004, Munhoven 2007), equivalent
      to 5–20 years of industrial emissions. Conversely,
      an increase in calcification would increase
      CO2 levels by a similar amount (carbonate counterpump).
      Coupled climate-carbon models are
      increasingly revealing feedback mechanisms, which
      were completely unpredicted from first principles.”
      comment: oooops… but then it is just a model.
      “From a geological perspective, there is
      nothing remarkable about the magnitude of climate change we
      are experiencing now, except that it appears to proceed at a faster
      pace and starts from a warmer baseline.”
      comment: more oooops.
      “Without exception, all physicochemical climate stressors
      drive changes in phytoplankton species composition,
      but the precise direction of such changes (i.e., whether they may lead to HABs)
      remains largely unpredictable in view of our current incomplete
      knowledge of phytoplankton ecophysiology.”
      “Predicted global change will occur gradually over decades, allowing
      for adaptation of species to perhaps become genetically
      and phenotypically different from the present
      population. Laboratory studies should aim to mimic
      environmental conditions as closely as possible
      (Rost et al. 2008). A typical example is the problem
      of the potential impact of increased CO2 on the
      coccolithophorid E. huxleyi. Initial concerns focused
      on reduced calcification (Riebesell et al. 2000), but
      we now recognize that increased CO2 at the same
      time stimulates photosynthesis (Iglesias-Rodriguez
      et al. 2008).”

  5. “Diatoms play an important role in water quality and in the global climate.”
    And don’t forget about in pool filters!

    • And Kevin, terrestrial deposits of them are valued for their use as filtration medium for wines, beer, oils, absorbent medium for spills, kitty litter, and carriers for pesticides. Even the broken shells alone are a good organic pesticide because the jagged and sharp points and edges of broken silica shells tear the abdomens and thoraces of insects causing infection and dehydration! Deposits of their skeletons, called diatomite or diatomaceous earth are enormous. World production is over 2million metric tons, one third produced by the US. Most of this is lacustrine (from lakes), so they are a freshwater creature as well. “Food grade” is eaten by health nuts, a tablespoon or two a day- can’t for the life of me see how this insoluble pure silica can be a nutrient. It must scrape out the digestive tract or something??

  6. I don’t think sun color has changed noticeably enough to mean any difference for these organisms. What might be changing is color and light scattering properties of sea water in which they live.

    • UV levels can change much more than TSI between solar max and solar minimum.
      An excerpt from the Hallegraeff Review:
      “Whereas shorter wavelengths
      generally cause greater damage per dose, inhibition
      of photosynthesis by ambient UVB increases linearly
      with increasing total dose. In clear oceanic waters,
      UVB radiation can reach depths of at least 30 m.
      Although some phytoplankton may acclimate to,
      compensate for, or repair damage by UVB, this
      involves metabolic costs, thereby reducing energy
      available for cell growth and division. Raven et al.
      (2005a) suggest that UVB intensity affects the size
      ratio in phytoplankton communities because small
      cells are more prone to UVB and have comparatively
      high metabolic costs to screen out damaging
      UVB. Many surface-dwelling red-tide species of raphidophytes
      and dinoflagellates possess UVB-screening
      pigments, which give them a competitive advantage
      over species lacking such UV protection (Jeffrey
      et al. 1999). In some species, nutrient limitation of
      either N or P (from increased water column stratification)
      can enhance the sensitivity of cells to UVB
      damage (Shelly et al. 2002).”

  7. Biological turbidity in the oceans could well be effected by component variation in TSI. In turn, varying the depth of UV/SW absorption due to such turbidity effects ocean temperatures. This paper seeks to parametrise some of these effects to improve GCMs-
    – it contains a number of good references to similar work.
    Importantly the authors note –

    the climate modelling community has been slow to implement these parameterisations in OGCMs. As a first step, most models assume that all of the solar irradiance is absorbed at the surface in the same way that latent and sensible heat are passed across the air-sea interface.

    While it is encouraging that some are aware of the problem, the extent of this modelling problem is far greater than the authors indicate. While a step in the right direction, the parametrisations offered are still only “fiddling around the edges”. That UV/SW is absorbed at depth, not at the surface is the critical error in the very foundation of climate modelling. If you are not correctly modelling how solar radiation heats the oceans, then you cannot model climate.
    Solar heating of the oceans correctly modelled would show that the net effect of the atmosphere over the oceans (including all radiative processes) is cooling of the oceans. Climate models still try to show that the net effect of the atmosphere over the oceans is slowing the ocean cooling rate. The models will keep failing until this is corrected.
    The benefit of making such a correction would be that issues like TSI component variation and energy accumulation below the diurnal overturning layer could be studied with regard to longer term climate changes. The negative (from an alarmist perspective) of such a correction would be that it rules out AGW due to CO2.

    • “If you are not correctly modelling how solar radiation heats the oceans, then you cannot model climate”
      Yes Yes Yes!. Between how the ocean is heated via solar radiation, and how and where clouds form, about 85 % of what climate scientist need to know, is not known.

  8. A most excellent post, Anthony. I’ve long held that the ocean conditions don’t determine life, it works the other way around—life determines the ocean conditions.
    In addition to making lots of oxygen, phytoplankton (microscopic floating ocean plants) have some hidden effects.
    First, where there is no phytoplankton, the water is clear, and all of the absorbed solar energy is converted into heat. But when there is a lot of phytoplankton, much of the absorbed solar energy is not converted into heat. Instead, it is used in the making and breaking of chemical bonds, and in growing plant mass.
    Now, to be sure, this energy is eventually reconverted into heat, it’s the nature of entropy … but that may not happen at the surface of the ocean. It may happen, for example, in the abyss. In the abyss, there is a constant rain of organic stuff, bits and pieces of everything from phytoplankton to zooplankton to small fish to whales. When this organic detritus decomposes, it releases the energy it contained, energy it absorbed near the surface … but it releases it at the bottom of the ocean. In addition, some of the energy is used to create gases (including both oxygen and CO2) that leave the ocean entirely. So when that oxygen rusts a bit of iron at a later date, the energy is released on land rather than in the ocean.
    Next, phytoplankton significantly change the vertical thermal structure of the ocean. Phytoplankton are plants, so as one might expect, they are all in competition for the light. As a result, they are thickest right at the surface. This means that instead of the solar energy warming the lower part of the mixed layer, it is absorbed right at the surface. So plankton make the surface warmer and the subsurface cooler.
    Next, the ability of ocean diatoms to utilize both red and blue light, while surprising, is logical. Every diver knows that the blue light penetrates deeply, but the red light is absorbed nearer the surface … so much so that if you cut yourself at depth, you bleed green. Since the competition is at the surface, we’d expect to find the diatoms using the abundant red light. But of course they need to be able to survive the times when they are deeper and get only blue light. The article says that in blue light they photosynthesize but they don’t grow … so they are “hibernating” when they are down deeper. Another unknown aspect of this marvelous world.
    Finally, an oddity. Plankton emit dimethylsulfide (DMS). This, in turn, forms cloud condensation nuclei, which favors the formation of clouds … how curious, that the smallest plants in the ocean should be able to affect the rate of cloud formation. And of course, the more light striking the surface, the warmer it is, the more DMS is produced … another lovely example of thermal regulation by emergent phenomena, in this case the emergent phenomenon we call “life”. There’s a good discussion of DMS and plankton here.
    To me, this is the best part of the extremely young and unsettled science of climate. There is something new to be learned every day.
    My best to all,

    • Willis says…”It may happen, for example, in the abyss. In the abyss, there is a constant rain of organic stuff, bits and pieces of everything from phytoplankton to zooplankton to small fish to whales…”
      Thank you for thinking about this. Anyone who has developed a compost pile has some understanding of the heat released. The “ocean snow” must be massive, and I have been curious about what, if any, role this has in how much energy is absorbed, and later released from the ocean floor. I am curious if this plays a role in the steady state temperature of the deep oceans.

  9. I would add that a very brief discussion of some of the issues raised in the Sweeny et al paper occurred in 2005 at Climate Audit –
    The thread contains a truly hilarious gem from Gavin –

    Differences in the physics of SW and LW heating in the ocean are important and are treated consistently in all current climate models.

    Given that failing to correctly model the “Differences in the physics of SW and LW heating in the ocean” is the most critical failure in climate modelling, I’d call that “comedy gold” right there 😉

  10. Interesting that diatoms emit cloud condensation nucleii (DMS) when clouds are detrimental to them (albedo). There needs a lot more study in order to fully understand diatoms.

      • they do not thrive without sunlight- do clouds block UV ? I don’t believe so, but they do block visible light. Why do diatoms emit a substance that leads to less visible light? Needs more study.

  11. Very interesting, thanks. Looks like more of a future in this work than in extraxting sun-beams out of cucumbers.

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