Snowfall at the equator

Marine snowfall at the equator

GEOMAR team publishes a detailed picture of the biological particle flow into the deep sea along the equator


The great ocean currents with their immense energy transport have a decisive influence on the atmosphere and thus the climate. But besides this well-known fact life in the seas also plays an important role for climate-related processes. Especially the smallest creatures, tiny planktonic organisms, take up carbon near the surface, process it, build up their bodies with it or excrete it. The carbon incorporated in the excretory products or dead organisms then sinks to the seabed. The constant flow of organic particles towards the deep sea is also called “marine snowfall”.

This snowfall is most intense where strong biological primary production can be observed near the surface. This for example is the case along the equator in the Pacific and Atlantic Ocean. However, it is hardly known how the particles are distributed at depth and which processes influence this distribution. Now, an international team of scientists led by the GEOMAR Helmholtz Centre for Ocean Research Kiel has published the first study with high-resolution data on particle density in the equatorial Atlantic and Pacific Ocean down to a depth of 5000 meters in Nature Geoscience. “The analysis of the data has shown that we have to revise several previously accepted ideas on the flow of particles into the deep sea,” says Dr. Rainer Kiko, biologist at GEOMAR and lead author of the study.

The team, which includes colleagues from France and the US, has analyzed data collected during several expeditions of the German research vessels METEOR and MARIA S. MERIAN, the US research vessel RONALD H. BROWN and the French research vessels L’ATALANTE and TARA. The data were obtained with, among other sensors, the so-called Underwater Vision Profiler (UVP). The UVP is a special underwater camera that can be lowered down to 6000 m depth. During the decent, it takes 10 images per second, which allows particles to be counted and small plankton organisms to be identified.

“Up to now, it was usually assumed that we have the largest particle density close to the surface and that it decreases continuously with depth,” explains Dr. Kiko, “our data show, however, that the particle density increases again in 300 to 600 meters of water depth”. The researchers explain this observation with the daily migratory behavior of many plankton organisms, which retreat into corresponding depths during the day. “This depth seems to be the loo for many species. That’s why we find a lot of particles there,” says Dr. Kiko.

These microscopic particles very slowly sink deeper and are still detectable at 5000 meters depth. “This is also surprising, because it has been assumed that only few larger, rapidly sinking particles can be found deeper than 1000 meters,” explains Dr. Kiko.

Thanks to the interdisciplinary collaboration of biologists and physical oceanographers, the team could explain yet another phenomenon. “In the equatorial region, the flow of particles into the deep sea is much greater than in regions that are only 100 kilometers further north or south,” says Dr. Kiko. Prof. Dr. Peter Brandt, an oceanographer at GEOMAR, provides the explanation: “There are strong, eastward flowing deep currents north and south of the equator, both in the Pacific and the Atlantic. They form natural barriers that prevent further north-south propagation of the particles.”

All in all, the scientists were able to show the importance of biological and physical processes for the biological carbon pump. “Of course, we need further observations on the distribution of different planktonic groups in the ocean in order to further refine the image,” emphasizes lead-author Dr. Kiko. At non-scientists can help in the task to sort the enormous amount of plankton images the UVP delivers. “On the PlanktonID website interested people can help us to identify zooplankton, but they will also find additional information on the current study, such as the functioning of the UVP,” adds Dr. Kiko.



53 thoughts on “Snowfall at the equator

  1. As I have said, no one really knows how much carbon is sequestered
    by the oceans, and therefore, no one really knows how the carbon balance

    • Yup. +1

      There is always more. For example, I recall reading that E. huxleyi changes in size with varying CO2/carbonate/bicarbonate concentrations, which should affect sedimentation rates. We can be pretty sure that many such changes are not included in any climate model used by the IPCC.

    • Daveb, why would you suppose that some of the carbon will dissolve
      as it sinks? The deep ocean water gets colder, thus increasing its CO2
      “carrying” capacity.

      • Because the “carried” CO2 is in solution in the water. With a higher ability to absorbed dissolved CO2 one would expect that more calcium carbonate would dissolve.

  2. The equatorial currents are merely transporting the plankton elsewhere. One might look at where the currents lose some velocity and allow the suspended particles to drop out of the column. You might see some “snow drifts” there.

  3. When presented with an abundance of CO2, the oceans make limestone and other carbonate rocks. The more CO2, the faster the process…

    Lisa L. Robbins1, Kimberly K. Yates1
    (1) U. S. Geological Survey, St. Petersburg, FL

    Abstract: Microbial calcification: implications for marine whitings and inorganic carbon cycling

    Microbial calcification has been identified as a significant source of carbonate sediment production in modern marine and lacustrine environments around the globe. This process has been linked to the production of modern whitings and large, micritic carbonate deposits throughout the geological record. Recent research has advanced our understanding of the microbial calcification mechanism as a photosynthetically driven process. However, little is known of the effects of this process on inorganic carbon cycling or of the effects of changing atmospheric CO2 concentrations on microbial calcification mechanisms.

    Direct measurements of air:sea CO2 gas fluxes and carbonate sediment production rates were measured in whitings located on the Great Bahama Bank and in laboratory cultures of calcifying cyanobacteria and unicellular green algae. In situ gas flux measurements showed a reduction in atmospheric CO2 relative to adjacent waters outside of whitings. Similar results were also observed in laboratory cultures. Calcification rates in whitings and laboratory cultures ranged from approximately 0.06 to 34.5 g CaCO3m-3h-1. These results suggest that production of microbial carbonates may serve as a sink for inorganic carbon. Laboratory cultures of calcifying microbes were subjected to biological buffers to examine the role of photosynthetic uptake of inorganic carbon species in calcification. Results from these experiments indicate that microbial calcification mechanisms depend upon the species of inorganic carbon available to cells for photosynthesis and, thus, atmospheric CO2 concentrations. These results suggest fluctuations in Phanerozoic dominance trends for calcareous cyanobacteria and algae may be linked to fluctuations in atmospheric CO2.

    AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana

    Microbial lime-mud production and its relation to climate change
    AAPG Studies in Geology 47-14
    K.K. Yates and L.L. Robbins
    Edited by:
    L.C. Gerhard, W.E. Harrison, and B.M.B. Hanson

    Microbial calcification has been identified as a significant source of carbonate sediment production in modern marine and lacustrine environments around the globe. This process has been linked to the production of modern whitings and large, micritic carbonate deposits throughout the geologic record. Furthermore, carbonate deposits believed to be the result of cyanobacterial and microalgal calcification suggest that the potential exists for long-term preservation of microbial precipitates and storage of carbon dioxide (CO2). Recent research has advanced our understanding of the microbial-calcification mechanism as a photosynthetically driven process. However, little is known of the effects of this process on inorganic carbon cycling or of the effects of changing climate on microbial-calcification mechanisms.

    Laboratory experiments on microbial cellular physiology demonstrate that cyanobacteria and green algae can utilize different carbon species for metabolism and calcification. Cyanobacterial calcification relies on bicarbonate (HCO3–)utilization while green algae use primarily CO2. Therefore, depending on which carbonate species (HCO3– or CO2) dominates in the ocean or lacustrine environments (a condition ultimately linked to atmospheric partial pressure PCO2), the origin of lime-mud production by cyanobacteria and/or algae may fluctuate through geologic time. Trends of cyanobacteria versus algal dominance in the rock record corroborate this conclusion. These results suggest that relative species abundances of calcareous cyanobacteria and algae in the Phanerozoic may serve as potential proxies for assessing paleoclimatic conditions, including fluctuations in atmospheric PCO2.

    • “When presented with an abundance of CO2, the oceans make limestone and other carbonate rocks. The more CO2, the faster the process…”

      This is Le Chatelier at work, and the reason that the oceans will not “acidify”.

      • Yep. The oceans literally cannot become acidic. Seawater in close proximity to volcanic CO2 vents doesn’t even become acidic. The pH stays above 7.

        High CO2 (>2,000 ppm) is associated with low-Mg calcite carbonate deposition. Low CO2 (<1,000 ppm) is associated with high-Mg calcite and aragonite carbonate deposition…

        The oceans are actually very good at carbonate geochemistry.

      • Hence no surprise that the aragonite-shelled ammonites perished in the end Cretaceous mass extinction, while the mainly calcite-shelled nautiloids survived.

    • And do not forget that there are areas of the oceans where there are puddles and lakes of LIQUID CO2. Or at least 10years ago that is what was reported, unable to find the link now.

  4. Climate science will probably never be settled, but to imagine it is now is ludicrous. We don’t even know all the carbon sinks, or even sources, let alone how rapidly they work.

    Climatology is still in its infancy, and its growth has been stunted for decades by CACA, which should have been laughed out of Hansen’s overheated hearing room in 1988.

  5. The USEPA says that upland topsoil in the US is a CO2 sink, supposedly
    absorbing TG 30 per year.

    It is not a sink. It is a source.

    Pick a smooth level spot on some good upland topsoil (not in a floodplain),
    take a large stainless steel salad bowl, invert it, and put a reasonably
    sensitive CO2 meter under it, set it on continuous read mode, and put
    a ten pound weight on top of your inverted salad bowl. The winds need
    to be near calm. Retrieve the meter 12 hours later.

    When I did this test recently, ambient CO2 was 404 ppm. When I retrieved
    the meter 12 hrs later, it read over 950 ppm.

    It is a simple, easy to do test, and it proves that upland soil is a source, not
    a sink of CO2.

    • CO2 at the surface can be quite a bit higher than the ambient level… And your salad bowl was only capturing one direction of the carbon flux. The soil could still be a net sink.

      • CO2 level in the soil and close to the surface is almost always much higher than in the free air, particularly in forests or shrub where air circulation is restricted. And, yes, there is almost always a net flow of CO2 from the ground into the air, but there is also almost always a flow of organic material (=carbon) into the ground and it is usually bigger than the CO2/CH4 outflow measured as quantity of C.

      • David,
        The hydrocarbons which the microbes are oxidizing is upwelling
        natural gas. The test which I used to prove that is also simple, but much
        more arduous to execute.

        In the same topsoil which I tested for CO2 at the surface, I also dug a test hole
        through the topsoil into the subsoil, through any sign of worm casting or roots
        or other possible contributors to decay, inverted a similar ss bowl, drilled a hole
        in the center of the now top, soldered in a compression gas fitting, and attached
        a 1/4 ” copper pipe. I extended the pipe above the level of the topsoil and
        attached a closed gas valve, and refilled the hole.

        After 24 hrs I attached a hydrocarbon detector to the gas valve and received
        a positive reading.

        I did this test first in Kansas, but have since done it in several places, including
        on my own property in the Tennessee Valley, and always have gotten a
        positive reading for hydrocarbons.

        The consumption of natural gas by microbes in soil with adequate moisture
        is responsible for the richness of the top soil. The more upwelling
        hydrocarbons, the richer the topsoil, and the more CO2 that will be read
        the surface. I have found no upland topsoil which consumes from
        the surface.

        I mis-stated above. The USEPA listed US soil as a 30tg sink for methane,
        not CO2. Sorry for the mis-statement.

    • Hi 5 and big respect Jerry.
      Is your meter still alive and ideally connect-able to a computer?

      I say that as CO2 meters seem to be rather fragile and expensive, certainly the Swedish made infra-red sensor they use. Maybe I abused mine.
      But, initially, I ran the same experiment as you, on the lawn of my garden and using large plastic (about 100 liter) sized tubs that farmers buy mineralised cattle feed supplements in.

      I ran the tests for just 5 minutes at a time, 5 mins under the tub and 5 minutes back in the fresh air to ‘reset’ the meter.
      The soil loses huge amounts of CO2, during summertime when the soil is warm.
      Repeat using the same plastic tub, the same CO2 meter on the exact same bit of dirt in the winter and the meter records no change.

      Then I cut the bottom out of the plastic tub and resealed it with clear polythene.
      Under a bright sun, in summer, the reading goes down. Same everything but blank off the plastic window and the reading goes up.

      Then and what probably killed my CO2 meter, I fixed it up on the lawn with just a wind and rain shield over it (basically a Stephenson screen) and ran a long USB lead to a little PC on the kitchen table and just let it run, recording the reading every 10 minutes.
      In summertime, the daytime lows (4 or 5 PM) went down to 380ppm and the rose to 620ppm in the hour before sunrise. (My meter also recorded temperature. Strange that the CO2 reading went in exact antiphase to the temp reading. Maybe my meter just misunderstood the GHGE)

      During winter months, the daytime, nightime, morning and afternoon readings were all about the same – shade over 400ppm.

      Thank you Mr Bill Gates for your shonky software and the need to replace computers to run it and hence the disappearance/loss of my epic collection of bookmarks, but I could have pointed everyone to an experiment some researchers did in a farmer’s field not far from where I was in NW England.
      A farmer ploughed his field (an old cow-pasture) and let the researchers plant some CO2 meters across it while it lay fallow.
      They recorded a loss of CO2, from the ploughed dirt, of 10 tons per acre per year.
      Typical crap SW Scotland weather meant the farmer couldn’t replant his field for another year and the experiment continued.
      The field lost another 10 tons of CO2, per acre, in the following year.

      Another bookmark I lost and cannot find was where a CO2 meter was put on some overgrown and unmanaged land near a big city centre.
      Everyone expected it to be a carbon sink. Big plants growing well, warm environment and no man-made disturbance (cutting harvesting or the like)
      That city centre dirt patch was also pumping out CO2 at nearly 10 tons per acre per year. The researchers admitted to not having a fooking clue why.
      I say simple. NOx from traffic exhausts was fertilising the plants and the soil bacteria and it was they that were making all the CO2.

      So. Farming takes up 10% of the world’s land area = 5 E13 square metres= 5 E9 hectares of which maybe 50% is regularly ploughed so lets say 5 E9 acres
      At 10 tonnes per acre of CO2, that is 50E9 (50 gigatonnes) per year of CO2

      What about the nitrogen unfertilised city centre patch. It should have been sinking CO2 but was sourcing, at 10 tonnes per acre.
      Almost all farmland gets some nitrogen fert either as bagged fert or manure so does nitrogen application promote 20 tonnes per acre of CO2 release to explain the city centre patch. (The plants were sinking 10 tonnes but as the patch still sourced 10 tonnes. yes?)

      So for all farmland , 10 giga acres roughly, at another 10 tonnes is 100 gigatonnes of CO2 sourcing, plus the 50 gigatonnes from ploughing to get just approximately 150 giga tonnes per year coming out of farmland.
      Before you cut and burn any forest anywhere.
      Also, we’ve got water soluble nitrogen raining down everywhere, that’s what’s making the planet go green.
      How much extra CO2 is coming from all the soil bacteria that this ‘wild nitrogen’ feeding? Another 50 giga tonnes? Per year.

      Makes all this emissions accounting at about 30 or so giga tonnes, look really pretty poxy and pointless doncha think?

      • Peta from Newark
        I appreciate your experiments and calculations, but the output of CO2 in a given
        plot of ground depends (mostly) upon the input of hydrocarbons from below.

        Foliage which is not fertilized or harvested tend to almost balance out over time.
        The fertilizer naturally introduced from above makes a small addition yearly to
        the soil if nothing is removed.

        In areas where the shield is near the surface, as it is in the Atlanta, Ga.
        area, the granite blocks the upwelling hydrocarbons and the soil is nutrient
        poor red clay and the cotton crops sucked all the accumulated value out of the
        in a relatively short time. The output of CO2 would be small.

        The topsoil in Kansas is very deep and a large supply of natural gas, relatively,
        replenishes,(feeds the microbes), on an ongoing basis. The shield is very deep
        and the near surface rock is carbonaceous allowing the flow of upwelling

        The soil organic content, SOC or soil maps give a good indication of the relative
        amounts of natural gas available to the microbes to enrich the soil,
        again if there is enough water present to keep the microbes happy. This variation
        would make an accurate count of total CO2 output of soil very difficult.

    • Jerry Henson
      October 10, 2017 at 2:01 pm: You have blocked the light, wiping out photosynthesis. But respiration continues. Artificial night, no CO2 reduction, only oxidation, hence more CO2. A thin transperant bowl might do better, if it does not too hot inside.

    • I think tty is probably correct. Why not retry your experiment on a reasonably sunny day, but use a transparent glass or plastic salad bowl and pick a patch of topsoil with grass or other photosynthesizing organisms growing. Measure again after 24 hours.(Plants absorb CO2 in daylight and respire it at night). My GUESS is that you might observe a small net decrease in CO2 due to conversion to organic molecules that will eventually end up in the topsoil. … or not. Lot’s of other factors to consider like the possibility that your ad hoc “greenhouse” might get too warm during the day for the photosynthesizing organisms to survive..

      • Don K.
        I have done the test in the winter when the foliage was dead but the ground
        was not frozen, to a similar result.

  6. Interesting new study on irregularities in marine snowfall. Is a new small part of a much bigger picture that has large fossil fuel and carbon sequestration implications.
    Marine snow actually has three main components: organic carbon (think dead Cyanobacteria, algae, or coccolyths), calcareous skeletons (think dead coccoliths and forams), and silicaceous skeltons (think dead diatoms and radiolarians). What becomes of the resulting seafloor ‘snowdrifts’ depends.
    All the organic carbon will be consumed by ‘decay’ aerobic ocean bacteria unless it falls into anoxic bottom water. Interestingly, the harder the marine snowfall (‘blizzard conditions’) the greater the likelihood of anoxic bottom conditions (the Summer Gulf deadzone off the Mississippi mouth is an example). Under anoxic conditions the snow will eventually form a kerogen shale (organic=>kerogen together with various proportions of carbonates and silicates) like Colorado/Utah’s Green River formation with its fantastic ~55mya fish fossils. If it then later undergoes catagenesis it forms an oil/gas shale like the Bakken. The bottom of the Black Sea is such a present day anoxic environment, explaining the magnificently preserved shipwrecks from Greek and Roman times at 1000 meters.
    All the inorganics will form a bottom ooze and eventually sedimentary rock. But the nature of the rock depends greatly on depth by something called the calcium compensation depth (actually, there are two: calcite and aragonite). Carbonates stable at sea surface conditions increasingly disassociate with depth. The disassociation rate depends on temperature (lower=>faster), pressure (higher=>faster), and dissolved CO2 (higher=>faster). So there is a deep ocean depth (CCD) below which no carbonates and only silicates survive over geologic time. In the central Pacific CCD is ~4000 meters. In the North Atlantic it is ~5000 meters. So we know that carbonate oil shales like Bakken were originally (a) anoxic and (b) ‘shallow’ bottomwaters. And we know all the thick ‘limestone’ formations are from coccoliths and forams in ‘shallow’ waters. The White Cliffs of Dover are an example: chalk from coccoliths. Literally a marine snowdrift.

  7. “Especially the smallest creatures, tiny planktonic organisms, take up carbon near the surface, process it, build up their bodies with it or excrete it. The carbon incorporated in the excretory products or dead organisms then sinks to the seabed.”

    Except that mostly it doesn’t. This “rain” of organic material is what everything below the photic zone is living on. There is no primary production where there is no light. Most of the “rain” gets eaten even before it reaches the bottom and the rest is taken care of by bottom-living organisms. There is practically no accumulation of organic material on the deep seabottom. The only exception is where the bottom is anoxic (in the Black Sea for example), however the deep ocean is normally pretty well oxygenated.
    And what about the indigestable parts of organisms? They are mostly calcite or aragonite and dissolve once they have sunk below the CCD (Calcium Compensation Depth, usually 3000-4000 meters). About the only that does accumulate on the deep ocean bottom is siliceous shells “radiolarian ooze”.

    So, sorry, very little coal accumulates in the deep ocean though a lot of calcareous sediments does accumulate on the continental shelves and above to CCD. Instead it gets metabolized by organisms and turned into CO2 which ultimately turns up in upwelling areas where deep ocean water returns to the surface.

    I suppose most of you have read the horror stories about sea-water the is so “acid” that it dissolves pteropod shells. It does happen occasionally, but not because of more CO2 in the air, it happens in areas where high-CO2 abyssal water upwells. That water has spent something like 1,000 years in the deep sea and a lot of the oxygen in it has been converted to CO2. Such water is rich in other nutrients as well, which is the reason that almost all the prime fishing areas of the World are found in those upwelling areas with their frightful “acid” water.

    • Good summary, except that at seafloor vents far out of the photic zone there are communities living off chemosynthetic primary production other than from photosynthesis and detritus falling from above, where the sun shines.

      • WP, the communities at the seafloor vents are living on hydrocarbons which
        are eaten by microbes, which in turn are eaten by filter feeders, etc.

      • Jerry

        Plus the sulphur-based food chains. There are little worms living in the rocks (eating rock) at 16,000 ft below Johannesburg. A lot happens where the sun don’t shine.

    • I suspect there is much more to it than a simple examination of the oxygen budget suggests.

      Organic carbohydrates are biochemically disproportionated into CO2 and methane, allowing for carbon ‘escape’ from the oceans as gaseous products without the need to invoke oxygen. Just how did those gargantuan deposits of methane hydrates come about? I’ve not yet seen a complete and convincing argument.

      • The large deposits of methane hydrates are actually natural gas hydrates
        and the gas which feeds them rises from deep in the earth, until it hits
        the combination of pressure or temperature which turns it into a hydrate.
        This temperature/pressure curve is known as the zone of stability. The
        colder it is, the less pressure required to form the hydrate.

        Off the coast of North Carolina is a zone of hydrates appx. 500 meters
        thick. This is about 500 feet under what appears to be the ocean floor.

        The layer of hydrates accumulate until the pressure is enough to stem
        the upflow, like a cork in a bottle. When some of that pressure is relieved,
        more will flow up.

        Some people believe that the hydrates are an accumulation of millions
        of years of plant life falling to the ocean, generating methane. The Deep
        Water Horizon spill shows us that the microbes in the ocean will not
        allow this to happen.

        When scientist went into the Gulf three months after the well was capped to
        survey the spill, it was gone. The hydrocarbon loving microbes had eatten
        it all. The microbes bloom to the extent of the food available. These
        microbes would not allow food which they can access to reach the ocean floor.

        It is natural gas, not just methane.

  8. There is a very interesting literature on marine snow, no doubt larger than my awareness. There is evidence that mullet eat it, not their best diet, larvae are attracted to it (gobble, gobble?), one paper called it a “biocoenosis” and one experimental and modeling paper concluded, you guessed it, how very complicated it was. As noted sounds like the paper deals in real data, would like to see it done more somehow, as importance also noted above, in turbid waters. Suspect results would be, well, turbid. By the way the erroneously named dead zone is not metabolically dead, just looks that way and I am told it sells newspapers.

  9. No gratuitous reference to the “the end to is nigh”. Only a subdued plea for more money. And interesting too. Clearly not the work of climate sciencyists.

  10. So,,,Take all of that deep water below the Calcium compensation depth (CCD) where CaCo3 is dissolved creating higher concentations of CO2 at Low temp (~4 deg C) and High pressure (~6000 psi) conditions, and upwell it at a continental margin. As the rising water reaches surface conditions, the temperature of the upwelling water warms and the pressure decreases, the CO2 comes out of solution putting CO2 from ancient water back into the atmoshere. Has anyone accounted for this CO2?

    • I would guess that something like this is why the CO2 levels lag temperature rise by approx. 800 years. I think it certainly has to do with deep ocean upwelling cycles.

  11. Just pause for a moment that 99% of glaciologists and geographers today do not have any understanding of the physical properties associated to the works “snow”, “fern”, “ice” let alone “glacier ice”. Glaciologists and geographers today are like the Aztec Priests of Millennia ago, cutting off peoples heads thinking that doing such would induce more precipitation or lower what they misunderstood as temperature.

    • I can’t vouch for geographers but I know a few glaciologists and the physical properties of snow, firn and ice is what they are good at (not “fern” by the way, that is for botanists). What they tend to be a bit short of is historical geology.

  12. In general I don’t disagree with the article or most of the comments. I would comment that a lot of CO2 fixation in the oceans occurs in reef or intertidal settings and doesn’t depend on microorganism “snow”. Some of it is composed of bodies of corals, mollusks, corraline algae, etc. Some appears to be inorganic. The resulting beds can be quite thick — hundreds of meters, and are often resistant to erosion especially where Magnesium replaces Calcium to form dolomite instead of calcite.

  13. I don’t see how they “show the importance of biological and physical processes for the biological carbon pump.” They detailed the process, but they didn’t say what is so important about their discovery.

  14. I thought that this is what the article was going to be about:

    “The mountain itself poses almost no altitude limits – Cayambe, a volcano in Ecuador reaches to 5,790 meters. The interesting aspect of Cayambe is not that it is high. It is not even as high as some of its neighbours in Ecuador. But Cayambe is the only place on the equator that has snow. I’m here to ski on the equator…”



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