The phytoplankton decline, is there anything to it?

By Andy May

We have been told that the phytoplankton population is declining rapidly around the world and, of course, the cause is climate change. Phytoplankton is the base of the ocean food chain and it accounts for about half of global primary productivity or organic matter creation (Boyce, Lewis and Worm 2010). Phytoplankton is the major consumer of carbon dioxide, the dreaded demon trace gas, and the major producer of oxygen. So, first question, is the estimated decline in phytoplankton accurate, significant or unusual? Second question, if the decline is real, are the measurements long term enough to show it is not a natural occurrence? What is the natural variability and how do we know man-made climate change is to blame? Let’s investigate this.

The purported problem

An article in Nature (Boyce, Lewis and Worm 2010) entitled “Global phytoplankton decline over the past century” was widely read and discussed at the time. The following is from the paper:

“We conclude that global phytoplankton concentration has declined over the past century; this decline will need to be considered in future studies of marine ecosystems, geochemical cycling, ocean circulation and fisheries.”

They conclude that the decline is due to higher sea surface temperatures (SST). This is somewhat counter-intuitive since higher temperatures usually correlate with more plant growth, not less. But, they state that their conclusions and the decline are “unequivocal.”

Over the following year numerous critical replies were also published in Nature, one had the title “Is there a decline in marine phytoplankton?” (McQuatters-Gollop, et al. 2011). The following is from this reply:

“Boyce et al. compiled a chlorophyll index by combining in situ chlorophyll and Secchi disk depth measurements that spanned a more than 100-year time period and showed a decrease in marine phytoplankton biomass of approximately 1% of the global median per year over the past century. Eight decades of data on phytoplankton biomass collected in the North Atlantic by the Continuous Plankton Recorder (CPR) survey, however, show an increase in an index of chlorophyll (Phytoplankton Colour Index) in both the Northeast and Northwest Atlantic basins …, and other long-term time series, including the Hawaii Ocean Time-series (HOT), the Bermuda Atlantic Time Series (BATS) and the California Cooperative Oceanic Fisheries Investigations (CalCOFI) also indicate increased phytoplankton biomass over the last 20–50 years. These findings, which were not discussed by Boyce et al., are not in accordance with their conclusions and illustrate the importance of using consistent observations when estimating long-term trends.”

There are other replies in Nature critical of the Boyce, et al. thesis that phytoplankton is declining, including (Mackas 2011) and (Rykaczewski and Dunne 2011). The extensive criticism led Boyce, et al. to publish two follow up papers, one in 2012 in Limnology and Oceanography Methods (Boyce, Lewis and Worm 2012) and another in 2014 in Progress in Oceanography (Boyce, et al. 2014). Thus, we appear to have conflicts between different datasets. Another discussion, regarding data in the Indian Ocean is very similar. A paper published in Geophysical Research Letters (Roxy, et al. 2016) states:

“Earlier studies had described the western Indian Ocean as a region with the largest increase in phytoplankton during the recent decades. On the contrary, the current study points out an alarming decrease of up to 20% in phytoplankton in this region over the past six decades. We find that these trends in chlorophyll are driven by enhanced ocean stratification due to rapid warming in the Indian Ocean, which suppresses nutrient mixing from subsurface layers. Future climate projections suggest that the Indian Ocean will continue to warm, driving this productive region into an ecological desert.”

OK, earlier studies show the largest increase in phytoplankton ever recorded, but our study finds an “alarming” decrease due to warming that will turn the Indian Ocean into a desert if the global climate models are correct. We sense some ambiguity and uncertainty, perhaps a closer look at the data and measurement methods is warranted. After all, it is just barely possible that the data isn’t good enough or definitive enough to draw such extraordinary conclusions. We are confident that the climate model projections are not very accurate.

Ocean phytoplankton overview

The ancestors of photosynthetic eukaryotes or the larger variety of phytoplankton evolved over 1.5 billion years ago and radically changed the world by consuming carbon dioxide and increasing the oxygen content of the atmosphere from nearly zero to 20% by the beginning of the Cambrian 540 million years ago. The first photosynthesizing organisms were probably very similar to modern cyanobacteria, a primitive variety of ocean dwelling phytoplankton. Cyanobacteria have no shell, are very small, and may be the origin of photosynthetic organelles in plant cells called chloroplasts. All phytoplankton live in the upper layers of the ocean in the “euphotic zone” or the part of the ocean that has enough light from the Sun for photosynthesis. Photomicrographs of some larger phytoplankton are shown in figure 1 from a paper in Science in July 2004 (Falkowski, et al. 2004) called “The Evolution of Modern Eukaryotic Phytoplankton.”

Figure 1, Phytoplankton photomicrographs. A: Diatom chain, B: a diatom valve, C: a tropical coccolithophore, D: a pair of phycomas, E: a clump of coccospheres, F: an athecate dinoflagellate, G: a thecate dinoflagellate. Source: (Falkowski, et al. 2004).

The early phytoplankton were very different from the species that dominate the oceans today. Modern phytoplankton evolved during the Mesozoic some 250 million years ago and are comprised of three large related types (or “clades”), the dinoflagellates, coccolithophores and diatoms shown in Figure 1. These clades all contain plastids of the original red algae and are descended from it.

Considerable doubt exists that humans are changing the climate, but there is no doubt that phytoplankton radically changed the world, as well as the climate, and most would say for the better. So why do we have so many very different interpretations of the data on phytoplankton abundance in the oceans? Phytoplankton are extremely important to the living Earth, the primary source of oxygen, the primary sink for CO2, and the ocean’s primary food source. If they are on a permanent declining trend, it is a big deal. We will frame the discussion by listing the objections to the original 2010 paper by Boyce, et al. and will follow these with the related comments from Boyce, et al. 2014.

Blending Bias, Mackas, 2011, Nature

David Mackas of the Institute of Ocean Sciences, Fisheries and Oceans in British Columbia, Canada (Mackas 2011) has reported in Nature that much, if not most, of the decline reported by Boyce, et al. (2010) is due to a bias created by blending the two data types they used. Boyce et al. pooled estimates of chlorophyll concentration from Secchi disks (Figure 2) and direct measurements from in situ profiles.

Secchi disks were invented in 1865 by Father Pietro Angelo Secchi to measure the clarity of the Mediterranean Sea. They are a 20 cm disk painted in bright contrasting colors. The ship’s crew lowers the disk into the ocean and notes the depth at which the disk becomes invisible. It was a standard measurement made by ships for nearly 100 years. In Figure 2 a Secchi disk is lowered from a ship on a 1949 voyage.

Figure 2. A photograph of a ship’s crew lowering a Secchi disk into the ocean in 1949 to measure water transparency. The image is from The Art Archive/R. Sisson/NGS Image Collection and copied from (Siegel and Franz 2010).

The in-situ measurements used by Boyce et al. are shipboard measurements of total chlorophyll pigment concentration. These measurements have been done on surface samples using spectrophotometry, fluorometric analysis or in vivo measurements of phytoplanktonic fluorescence over the past 100 years. Boyce and colleagues found a correlation between the in situ and Secchi disk measurements of the total chlorophyll pigment concentration. To do so they had to take the logarithm (base 10) of the concentrations first, the correlation coefficient of the logarithm of the concentrations was 0.77 for 13,700 samples. Since both measurements are in mg/m3 it is unclear why taking the logarithm was necessary, except to improve the correlation coefficient. The comparison is shown in Figure 3.

Figure 3. A plot comparing the Log10 Secchi disk derived total chlorophyll concentration to the Log10 in-situ Chlorophyll concentration and a map of the difference of the logarithms. Note a difference of one is an order of magnitude or a difference of 10 times. Source Boyce, et al. supplementary materials, figure S2.

In the text of the article Boyce, et al. report the correlation coefficient between the two concentration measures as 0.52, it rises to 0.77 after the log10 is taken of both concentration estimates. The logarithmic scaling reduces the apparent bias in that the Secchi disk estimates are biased high to the in-situ measurements by 25-50% throughout most of the measurements. Since the earlier measurements are mostly Secchi disk measurements and later measurements are mostly in-situ, the amount of bias is a function of time and this bias accounts for much of the one percent change per year documented by Boyce, et al. according to David Mackas (Mackas 2011).

In response to the criticism by Mackas and others (see below) Boyce, Lewis and Worm (2012) developed a new more comprehensive global database of chlorophyll concentration from 6 meters to 20 meters depth. The database uses a lot of data, including Secchi disk data, and is compared to satellite data but does not use satellite data. Besides limiting the depth range to 6 meters to 20 meters, they also do not include any measurements made in water with a total depth of less than 20 meters or within 1 km of a coast line. Phytoplankton exist in the top 100 to 300 meters of the ocean (Woods Hole Oceanographic 2018) so the volume investigated by Boyce, et al. is very small relative to the total volume of ocean containing phytoplankton.

In the 2012 database paper, Boyce and colleagues address this criticism by first calibrating all sources of chlorophyll concentration to a quality-controlled set of in situ measurements. This is an attempt to makes the various trends of measurements match, eliminating the systematic bias of the 2010 study.

Rykaczewski and Dunne (2011) Nature

This critique of Boyce, et al. (2010) is similar to Mackas (2011) but more detailed. Ryaczewski and Dunne examine the bias described by Mackas geographically and noticed that the bias was only 5% at low concentrations and >100% at high concentrations. Some of this trend may be due to taking the logarithm of the concentrations to build the function and then the anti-log to get the result. They also found that the bias was much higher in the Northern Hemisphere than in the Southern Hemisphere and that the pattern of the bias matched the pattern of the decline reported by Boyce, et al., see figure 4.

Figure 4. A comparison of the computed bias to the Boyce, et al. decline.

As we can see in Figure 4, the expected pattern of the bias is very similar to the pattern of decline in phytoplankton reported by Boyce, et al. in 2010. Rykaczewski and Dunne conclude, quite reasonably, that the reported decline is due to bias.

The critique of (McQuatters-Gollop, et al. 2011)

Probably the most devastating critique of Boyce, et al. (2010) was by McQuaters-Gollop, et al. (2011). Regarding the claim by Boyce, et al. that there has been a 1% decline per year in phytoplankton biomass, they wrote that Continuous Plankton Recorder (CPR) surveys in the Atlantic and Pacific show an increase in an index of chlorophyll, the Phytoplankton Color Index (PCI), as discussed in a quote from their paper in the introduction.

They found that more than 5 million nautical miles of ocean have been sampled by ships towing the CPR and more than 250,000 phytoplankton and zooplankton samples have been analyzed using a virtually unchanged methodology over the last 80 years and this data suggests that the concentration of phytoplankton in the oceans has increased. Figure 5 shows the Atlantic Phytoplankton Color Index data (PCI) from numerous CPR surveys.

Figure 5. The CPR surveys of phytoplankton concentration in PCI units for the North Atlantic.

Figure 5 shows that phytoplankton is increasing in the North Atlantic, precisely the opposite of the trend suggested by Boyce, et al. (2010). McQuaters-Gollop, et al. (2011) also found that if the Secchi disk measurements are removed from the Boyce, et al. database, the negative trends in the Atlantic and Pacific oceans reverse and become positive trends.

Boyce, et al. 2014

Boyce and colleagues reviewed all the criticism of their 2010 paper and, as a result, created a new database that is presented in their 2012 paper (Boyce, Lewis and Worm 2012). In the 2014 paper in Progress in Oceanography (Boyce, et al. 2014) they provide a new estimate of the trend in ocean phytoplankton concentration. Their new estimate, including the questionable Secchi disk measurements, showed a worldwide decline of 0.23% per year, about a quarter of the decline shown in the 2010 paper. In their global grid, 57% of the cells showed a decline in phytoplankton in the depth range studied, 6 meters to 20 meters.

It is significant that the weighted mean decline rate of the in situ measured data is significantly different from the Secchi disk decline rate for all trends and for statistically significant trends. This suggests, as McQuaters-Gollop (2011) noted that including the questionable Secchi disk data is critical to producing a declining trend. The differing distributions are apparent in Figure 6, from Boyce, et al. (2014).

Figure 6. Probability distributions of the logarithm of the Secchi disk concentrations in blue and the logarithm of the in situ measurements in red from all available data. This suggests either an actual change, since the early measurements are mostly Secchi disk estimates, or that the change seen in the study is dependent upon the distribution of Secchi disk estimates, source (Boyce, et al. 2014).

Discussion

Let us establish some basics about phytoplankton. It is important to remember that phytoplankton exists from the surface of the ocean to 200 meters or deeper over most of the world ocean, which covers 70% of the Earth’s surface. Some chlorophyll abundance and productivity depth profiles are shown in Figure 7.

Figure 7. Depth profiles for total phytoplanktonic carbon (Phyto C) primary production, phytoplanktonic production (PROD) and microzooplankton grazing (GRAZ) in the Costa Rica Dome area in July 2010, these measurements are 24-hour measurements from (Landry, et al. 2016).

In the Costa Rican Dome, phytoplankton are productive down to nearly 100 meters water depth, in other parts of the world they are productive to nearly 200 meters, sometimes even deeper. In Figure 8 we see total chlorophyll a, phytoplankton carbon biomass, and phytoplankton growth rate as a function of depth in offshore Hawaii. Significant growth is taking place at a depth of 140 meters.

Figure 8. Mean depth profiles for total chlorophyll a, carbon biomass, and phytoplankton growth rate offshore Hawaii from (Landry, Brown, et al. 2008). The “IN” profiles were conducted in an eddy being studied and the “OUT” profiles are the control outside of the eddy.

In Figure 8 it is significant that total chlorophyll and phytoplanktonic biomass can peak below 100 meters. As noted above, Boyce, et al., in both papers, only collected and used data from 6 meters depth to 20 meters depth. Even if they successfully sampled a significant portion of these depths over the entire world, it would only account for 9% of the euphotic zone, assuming an average depth of 150 meters. In many areas, such as Hawaii, they wouldn’t even sample the primary production zone.

Roxy, et al. (2016) report a decline in phytoplankton in the Indian Ocean, but readily admit that previous studies showed an increase. Every study shows that climate changes increase phytoplankton at some depths and decrease it in others. The phytoplankton will find an optimum depth where they maximize both the nutrient concentration and the available light from Sun. The best nutrient sources are in deeper water, and the best sunlight is shallower. The optimum depth changes with climate, season and weather. Sampling a thin layer from 6 meters to 20 meters, with the subject of your study moving up and down, often well outside that layer, due to climate change, season and weather, in an unpredictable fashion, is not ideal.

I appreciate the hard work of all these researchers, but frankly after reading numerous papers, I don’t think they have any idea if total plankton is increasing or decreasing or staying the same. They are sampling a huge ocean with a metaphorical tea cup. According to Boyce, et al. a record of plankton abundance of as many as 40 years is required to separate long-term natural trends from short term fluctuations (Boyce, et al. 2014). Given that the Atlantic Multidecadal Oscillation is about 60 years, more time than that may be required. Further, current high quality in situ data is very sparse and Secchi disk data is problematic. Satellite data is available for less than 30 years and very much affected by weather conditions and a shallow depth of investigation. Satellite data cannot distinguish between vertical movements of the phytoplankton population and their overall abundance. To make matters worse, different researchers using the same satellite data find plankton both increasing and decreasing globally (Boyce, Lewis and Worm 2010). Satellite data may never be adequate for this purpose. In short, this is an interesting and important scientific question, but the data we have available today is clearly unable to answer it.

Before I investigated this issue, I had seen Boyce, et al. 2010 cited in media reports many times. It is significant that I have not seen the rebuttals to their paper cited in media reports. Thus, a catastrophic decline in phytoplankton is reported, but extremely important, and valid, criticisms of the study are not worth mentioning? The media are a very poor source of information on science.

Bibliography

Boyce, D. G., M. R. Lewis, and B. Worm. 2010. “Global phytoplankton decline over the past century.” Nature 466. https://www.nature.com/articles/nature09268.

Boyce, D., M. Lewis, and B. Worm. 2012. “Integrating global chlorophyll data from 1890 to 2010.” Limnology and Oceanography Methods 10: 840-852. http://onlinelibrary.wiley.com/doi/10.4319/lom.2012.10.840/full.

Boyce, Daniel, Michael Dowd, Marlon Lewis, and Boris Worm. 2014. “Estimating global chlorophyll changes over the past century.” Progress in Oceanography 122: 163-173. https://www.sciencedirect.com/science/article/pii/S0079661114000135.

Falkowski, Paul, Miriam Katz, Andrew Knoll, Antonietta Quigg, John Raven, Oscar Schofield, and F. Talor. 2004. “The Evolution of Modern Eukaryotic Phytoplankton.” Science 305 (5682): 354-360. http://science.sciencemag.org/content/305/5682/354.full.

Fehling, Johanna, Keith Davidson, Christopher Bolch, Tim Brand, and Bhavani E. Narayanaswamy. 2012. “The Relationship between Phytoplankton Distribution and Water Column Characteristics in North West European Shelf Sea Waters.” PLOS. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3313960/.

Landry, Michael, Karen Selph, Moira Decima, Andres Gutierrez-Rodriguez, Michael Stukel, Andrew Taylor, and Alexis Pasulka. 2016. “Phytoplankton production and grazing balances in the Costa Rica Dome.” Journal of Plankton Research 38 (2): 366-379. https://academic.oup.com/plankt/article/38/2/366/2375234.

Landry, Michael, Susan Brown, Yoshimi Rii, Karen Selph, and Robert Bidigare. 2008. “Depth-stratified phytoplankton dynamics in Cyclone Opal, a subtropical mesoscale eddy.” Deep Sea Research II 55: 1348-1359. https://s3.amazonaws.com/academia.edu.documents/46414156/Depth-stratified_phytoplankton_dynamics_20160612-6046-1f7cvb2.pdf?AWSAccessKeyId=AKIAIWOWYYGZ2Y53UL3A&Expires=1521056786&Signature=DqsVgm7TdQA0WliY0yP0x6VwLy0%3D&response-content-disposition=inline%.

Mackas, David. 2011. “Does blending of chlorophyll data bias temporal trend?” Nature 472: e4-e5. http://imedea.uib-csic.es/master/cambioglobal/Modulo_V_cod101612/articulos%20para%20presentaciones_escoger/Boyce_etal_2011%20comments.pdf.

McQuatters-Gollop, Abigail, Philip Reid, Martin Edwards, Peter Burkhill, Claudia Castellani, Sonia Batten, Winfried Gieskes, et al. 2011. “Is there a decline in marine phytoplankton?” Nature 472. https://www.nature.com/articles/nature09950.

Roxy, Mathew Koll, Aditi Modi, Raghu Murtugudde, Vinu Valsala, Swapna Panickal, S. Kumar, M. Ravichandran, M. Vichi, and M. Levy. 2016. “A reduction in marine primary productivity driven by rapid warming over the tropical Indian Ocean.” Geophysical Research Letters 43 (2): 826-833. http://onlinelibrary.wiley.com/doi/10.1002/2015GL066979/full.

Rykaczewski, Ryan, and John Dunne. 2011. “A measured look at ocean chlorophyll trends.” Nature 472. http://imedea.uib-csic.es/master/cambioglobal/Modulo_V_cod101612/articulos%20para%20presentaciones_escoger/Boyce_etal_2011%20comments.pdf.

Siegel, David, and Bryan Franz. 2010. “Oceanography: Century of phytoplankton change.” Nature 466: 569-571. https://www.nature.com/articles/466569a.

Woods Hole Oceanographic. 2018. “Phytoplankton.” Know your Ocean. http://www.whoi.edu/main/topic/phytoplankton.

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85 thoughts on “The phytoplankton decline, is there anything to it?

      • Perhaps I’m just reading it wrong but…

        “Boyce et al. compiled a chlorophyll index by combining in situ chlorophyll and Secchi disk depth measurements that spanned a more than 100-year time period and showed a decrease in marine phytoplankton biomass of approximately 1% of the global median per year over the past century.

        Doesn’t 1% per year for 100 years equate to a 100% reduction?
        I guess we’re already dead but just don’t know it yet

      • -1% corresponds to x0.99
        -1% over 100 years corresponds to x (0.99)^100 = x0.37
        -1% over 100 years corresponds to -63%.
        But the -1%/year is all junk from junk science by junk scientist anyway.

    • I think all science majors should be required to take two years of statistical math – in their first two years of university. It’s apparent that a great number of “scientists” have no significant capability in the area. Further, it might be appropriate to require these studies to have an independent statistician to analyze the data – similar to what is required in many drug studies.

      • I think journalists should be required to take statistics. And if they report on science, at least one science class (with lab).
        I believe high school students should be taught to read statistics and understand probabilities and uncertainties and sources of error. They should also be taught to recognize propaganda and manipulation, and how to debate while taking the opposing view, how to discuss heated issues rationally and civilly…many of the things that adults never learned in a formal setting. I didn’t, anyway.
        Two years of stats at the beginning of college? Lots of people haven’t decided their major by then. And college calculus needs to come first. Some scientific fields use more stats than others, or different ones.
        A course in ethics would be good for all students.

  1. Andy May ==> Gads, you’re as bad as I am…giving the readers the straight-scoop with enough (and more…) information to actually understand the issue. Keep up the good work.
    PS: As usual, the overriding reality is “We Don’t Really Know….”

  2. Andy,
    59% vs 27% of the variation in one measurement can be explained in terms of the variation in the other measurement if one looks at the coefficient of determination, r2 rather than r. Logarithmic vs straight line. This is a very large difference and explains why a logarithmic curve fit was done if one is trying to push a point, or an agenda, unless one can explain why there should be a logarithmic relationship. This also shows why r2 should be used many times, rather than r, when considering the results of regression analysis as r2 actually has a meaning in terms of what % one variable’s variation explains of the other variable’s variation. I tried to explain this to another poster here on wuwt to no avail.
    Good article.
    Regards,
    JimG1

    • Perhaps the logarithmic curve fit was done to take into account Beer-Lambert Law for the water clouded by phytoplankton. Not much of a hidden agenda, IMHO.

      • You have, indeed, shown a potential reason for use of the logarithmic per Beer’s law. (I looked it up!) But my point regarding use of r2 vs r still stands. Square root of those fractional values gives much higher numbers than their squares and does not explain what percent variation in one variable explains of the other.

      • Perhaps the logarithmic curve fit was done to take into account Beer-Lambert Law

        That was my initial thought as well, but no.
        Two reasons:
        1) Both data sets are expressed as mg/m^3, so the logarithmic factor would have already been applied when calculating the concentration from the Absorbance reading.
        2) They took the log of *both* data sets, creating a log-log plot. This is not a log-linear plot as you would make in photometry.
        As an aside:
        When you make a standard Beer-Lambert Absorbance vs. concentration plot, what you are really plotting is the Log10 of 1/T vs. conc. (if you want to look at it this way) So it is really a log-linear plot.

  3. Since Blue Whales have a very direct food chain to phytoplankton, can their status be considered a bellwether?
    Blue Whales consume Krill
    Krill consume phytoplankton
    phytoplankton consume CO2

    • Also, thank you for this statement:
      “Phytoplankton is the base of the ocean food chain and it accounts for about half of global primary productivity or organic matter creation (Boyce, Lewis and Worm 2010). Phytoplankton is the major consumer of carbon dioxide, the dreaded demon trace gas, and the major producer of oxygen.”
      My one question would be about the ‘major producer of oxygen’, I don’t know of any other source for oxygen, but there is 500 times as much oxygen (20%) in the atmosphere as there is CO2 (.04%). All that oxygen came from CO2?

      • Thomas Homer ==> The overreaching understanding on atmospheric creation in geological time is that PLANTS, (starting with single-cells and up) which consumed CO2 and ‘exhale’ O2, are responsible for the high concentration of Oxygen in the atmosphere and that plants made it possible for ANIMAL life, which consumed O2 and exhales CO2.

      • All that oxygen came from CO2?

        On the early Earth, the atmosphere was largely CO2, methane and ammonia. Chemically, this is a strongly reducing atmosphere. All life forms at the time were chemosynthetic, and to them Oxygen was highly toxic. Then the first cyanobacteria came along, having learned the trick of photosynthesis. They reduced almost all the CO2 to hydrocarbons and liberated the O2, which was lethal to their chemosynthetic competitors. In relatively short order, they converted the atmosphere to largely Nitrogen/Oxygen which is strongly oxidizing, and took over the planet. In doing so, they nearly exterminated the chemosynthetic crowd.
        This is the first known example of chemical warfare on the planet.

      • Thank you Kip Hansen, Andy May and TonyL –
        This confirms my thoughts when looking at the atmospheres of three sister planets:
        – Venus … 95% CO2
        – Earth … 0.04% CO2
        – Mars … 95% CO2
        and knowing that:
        – Life consumes CO2
        … the conclusion is _________________

  4. Maybe they’re hiding from researchers like those Adélie penguins?
    https://www.nasa.gov/centers/goddard/news/topstory/chlorophyll.html

    Phytoplankton amounts have increased by 10.4 percent along global coast regions, where the ocean floor is less than 200 meters (656 feet) deep. Ocean plant life has greened the most in the Patagonian Shelf and the Bering Sea, and along the coasts of the Eastern Pacific Ocean, Southwest Africa, and near Somalia. Both the Patagonian Shelf and the California/Mexican Shelf showed large increases in phytoplankton concentrations of over 60 percent.

  5. Now you are in my realm. Early in my career we used Secchi disks. At the time it was assumed they were measurements of two parameters phytoplankton and turbidity. Some time in the 1970s several studies were done that indicated that Secchi measurements were very subjective, e.g., two trained technicians got different readings, they were poor measurements of phytoplankton but were OK measuring turbidity. When good submersible light meters came out we began to use those for turbidity. I “played” mainly in the tropical oceans with large pelagic fish. I had been taught in school that the tropical oceans were near deserts compared with temperate oceans. Yet varies species travel to tropical oceans to spawn, e.g., swordfish, sailfish, marlin, blue fin tuna and there are species that live primarily in tropical oceans that grow extremely fast, e.g. mahi-mahi (dolphin fish), yellow fin tuna. So primary productivity had to have been grossly underestimated in the past. I debated this issue for years with world phytoplankton expert. Finally someone decided to try and solve this paradox. They pulled plankton nets or samplers with much smaller mesh. They discovered micro-phytoplankton and hypothesized they were the basis of the tropical oceans food chain.

    • Edwin ==> ” I “played” mainly in the tropical oceans” — me too — sometimes in unrecomended ways. while my wife focused the underwater camera, I poked a sleeping six-foot nurse shark with a shark bit of coral debris so it would come out and have its picture taken with me…..

      • Kip, while I did actually play in the tropical oceans and had since I was eight years old also did research on large pelagic fish for the better part of 20 years. Today I say “play” because the research was often fun and usually exciting; sometimes frightened so. I had fallen in love with marine science by the age of 12.

      • you don’t have to spend too much time around the marine environment to fall in love with it edwin. i once turned down a job that came with a 30% pay increase as i would have to live just about as far from the sea as is possible in the uk.

    • Ah! Edwin, how interesting. That doesn’t surprise me, considering the vast diversity of filter-feeders in the tropics. Say, I was wondering if it’s true that there are more plankton in shallower areas – continental shelves, for instance? Or generally more along coastal areas? I suppose that would be where nutrients are high, where there is upwelling?
      Any opinion on the coral reef “debate”? Is bleaching a problem, potential problem, or nothing to worry about?
      There’s been talk that climate change and CO2 fertilization (and agricultural runoff due to flooding I suppose) could worsen red tides.
      I stumbled on a couple intriguing graphs the other day. “These lines indicate the average change in latitude and depth for 105 marine fish and invertebrate centers of abundance in the U.S., 1982 to 2013…..When combined with information on changing temperatures in the oceans around North America, these data suggest that climate may be driving many marine fish and invertebrates to shift north and deeper. These shifts affect fisheries by changing where, when and which species can be caught.”
      http://oceanadapt.rutgers.edu/national_data/

      • “if it’s true that there are more plankton in shallower areas – continental shelves, for instance? Or generally more along coastal areas?”

        Is there a difference?
        Then, consider that plankton are relegated to shallow depths. What difference does it make, if the total depth of plankton is around 200m? Or ranging from 100m to 300m?

        “Any opinion on the coral reef “debate”? Is bleaching a problem, potential problem, or nothing to worry about?”

        Classic red herring distraction fallacy. No relation to the topic.

        “There’s been talk that climate change and CO2 fertilization (and agricultural runoff due to flooding I suppose) could worsen red tides.”

        A) Another red herring distraction.
        B) Talk is cheap, as are rumors, innuendos and unsupported claims. List facts.

        “I stumbled on a couple intriguing graphs the other day.”

        A) read Willis’s excellent article “Data in Bondage”
        – – Massively lumped together data masks any underlying value and information.

        “U.S., 1982 to 2013”

        Which roughly matches the Atlantic Multi-decadal Oscillation (AMO).
        Which makes the statement “climate may be driving many marine fish and invertebrates to shift north and deeper” true. Only that climate effect is well known, absolutely natural and changes frequently each thousand years.

      • “if it’s true that there are more plankton in shallower areas – continental shelves, for instance? Or generally more along coastal areas?”
        Is there a difference?
        >>>To me there is
        Then, consider that plankton are relegated to shallow depths. What difference does it make, if the total depth of plankton is around 200m? Or ranging from 100m to 300m?
        “Any opinion on the coral reef “debate”? Is bleaching a problem, potential problem, or nothing to worry about?”
        Classic red herring distraction fallacy. No relation to the topic.
        >>>>Wasn’t talking to you, I was asking Edwin a question.
        “There’s been talk that climate change and CO2 fertilization (and agricultural runoff due to flooding I suppose) could worsen red tides.”
        A) Another red herring distraction.
        >>>>Hey, look over there!! That one’s blue!
        B) Talk is cheap, as are rumors, innuendos and unsupported claims. List facts.
        >>>>It is fact.
        “I stumbled on a couple intriguing graphs the other day.”
        A) read Willis’s excellent article “Data in Bondage”
        – – Massively lumped together data masks any underlying value and information.
        >>>>Then look at each region or species for more detail.
        “U.S., 1982 to 2013”
        Which roughly matches the Atlantic Multi-decadal Oscillation (AMO).
        >>>>Does that explain the pattern on the Pacific side?
        Which makes the statement “climate may be driving many marine fish and invertebrates to shift north and deeper” true. Only that climate effect is well known, absolutely natural and changes frequently each thousand years.
        >>>>This is reason in bondage.

  6. I simply don’t udnerstand how anybody can look at the photo and come to the conclusion that the data points to anything “unequivocally”?
    I came across a marvelous quote today that seems apt for much of this sort of stuff:
    “The model only reflects whatever spurious assumptions are put into it. Starting with the opposite assumptions would generate the opposite result. This is no route to a scientific finding.” Prof Peter Hajek
    The model was about e-cigarettes and generated 120 million young people in the UK who took up smoking because of e-cigarettes, despite our total population being only around 65 million.

    • “… I simply don’t udnerstand how anybody can look at the photo and come to the conclusion that the data points to anything “unequivocally”? …”
      —-
      It’s because your funding doesn’t depend on seeing what”s not there. 😉

    • …The model was about e-cigarettes and generated 120 million young people in the UK who took up smoking because of e-cigarettes, despite our total population being only around 65 million….
      Easily explained. Individuals are taking up smoking multiple times. I understand that people can perform the opposite exercise – giving up smoking – several times per day….

  7. I have repeatedly said that so much of our science is in its infancy, that we should not make conclusions and especially policies based upon it, until proof confirms it Yet, that is just what many scientist do with their data and then politicians do with it.

    • johchi7 – It doesn’t matter if “most” science is in its infancy (it that is even true). There is still quite a lot that is well-established. That is what should be used by policy makers, but when it comes to climate even the best-established science has been obscured by baseless assertions that it’s still too uncertain, the focus of scientific debate, etc.
      What do you want for “proof”? Who will you trust to give it to you? If you don’t trust scientists then you will never be satisfied until you can see for yourself whatever finally will convince you, and then it will be too late to mitigate. Ah, well. I don’t really care anymore. It’s already too late. Trump is taking us back to FF dependency and scrapping research into renewables – the science is immaterial.
      When the public loses faith in science it is truly a waste of money. So lets scrap all climate science! Someone else will deal with the future.

      • Proof requires something better than.
        It has gotten warmer.
        CO2 has gone up.
        Therefore CO2 caused the warming.
        Especially since proxy records going back millions of years show absolutely no correlation between CO2 and temperature.

      • Kristi Silber, Your comments actually support what I said, more than you my think. Just as Mark W pointed out in his comment. We could go back in history to point out all the debunked science that the rulers of governments used to create political stances on to govern their people and control them. All because that is what they believed at that time.
        First World Governments of today base most of their policies upon the CO2 being the cause of nearly every problem that mankind has today. That has increased the cost of everything because of increasing taxes on FF that every product produced has either been made from them, is dependent upon them for energy to grow, harvest, mine, process or deliver them. As that cost increases, their cost it increases and the taxes that governments get from them increases. The more the governments can demonize CO2 it increases their funding. All because they took the scientist stand that demonized CO2, for doing things that they had no proof of what it does, but based upon hypothetical “what ifs” they have distorted the whole world economy that has made some countries rich and kept other countries poor.
        What was the very first “scare tactic” that the demonized CO2 was to cause? Global Flooding, causing all the world glaciers to melt. Governments saw that as property losses of their coastlines, increasing rivers and lakes in-land that they couldn’t tax their citizens for if that land was under water and islands would lose most of their land masses. Other countries that had mountain glaciers may have gained land from the melting of them,but their lower lands would be flooded and that’s where the people lived, that had settled there after the Last Glacial Maximum ended and those mountains couldn’t grow crops. That one single scare tactic ideology of “Global Warming” scared the heck out of every countries governments. Taxes went up in every country on Fossil Fuels and to do it they created the “Fuel Shortage” scare and limited how much you could buy. While the “Smog Pollution” was being used to war on coal and gasoline Carbon Monoxide and dust pollution – that only affected small areas of the planet – it affected the whole planet economically.
        What we are now learning more and more, is that Carbon Dioxide has much less to do with Global Warming than it was hyped up to be causing. All while many were screaming that it never had any significant role in global temperatures in earth’s history. I’ll be extremely generous in saying that humans contributions of CO2 is only 1% of what nature and natural sources contribute. That 1% is not going to make any noticeable changes if every human on earth stopped every form of contribution this second, to the future climate, but it will cause the death of millions of people a year by exposure to the climate and food shortages.

      • Mark W:
        “Proof requires something better than.
        It has gotten warmer.
        CO2 has gone up.
        Therefore CO2 caused the warming.
        Especially since proxy records going back millions of years show absolutely no correlation between CO2 and temperature.”
        That is not an informative answer to, “What proof do you require?” “something better than” is just a bit too open-ended.
        Don’t forget there’s theory and prediction backing “It has gotten warmer”.and “CO2 has gone up”.from around 1900, growing confidence in the theory by the 1970s, including by Big Oil researchers. Not long after, the partisan split begins. Why? What would cause a political split in belief about a scientific question in the early 80s?

  8. Kudos on the excellent article — particularly its tone which is level headed and polite and avoids emotionally charged language. I wish all the posts here were like this one in that respect.

  9. I notice that they did not bother to find out whether there had been any changes in ocean temperature in the places whey the phyto plankton are allegedly declining.

    • Current temps have nothing to do with it….plankton is cultured within a ~40 degree range….lower temps they reproduce slower but live longer…..higher temps they reproduce faster but don’t live as long….end result like for like…current temps are about dead center on their range

  10. Having been trained long ago to use a Secchi disk, I can say that at best it’s an imprecise instrument. Determination of the disappearance depth is affected by the smoothness of the water surface, angle of sunlight, and the operator’s experience. Mixing Secchi data with data determined by other modern methods degrades the final result.

    • i have to say it sounds a bit like mixing ships bucket data with that of the intake systems. seems we may have been here before.

    • 2 days later and I agree. It is at best an imprecise instrument and when I was trained to use it–it was described as an OBSERVATIONAL tool, not a scientific instrument because of it’s inherent variability.
      What I don’t get is why the shallow depths? And at what time of day? Same time for each sample? What about vertical migration…that seems to be largely ignored.

  11. Anything in Nature is fake-science & has been for many yrs.
    Hey, I like that — fake-science. Describes most of it these days except for rare, obscure topics that haven’t been politicized yet.

  12. Baleen whale populations are reduced by hunting, and so could hardly act as plankton bellwethers. Conversely, plankton populations are influenced by consumer populations, which case probably renders negligible any climatic affect on plankton. In fact the claimed squid explosion in the Western Pacific may be due to a reduction of other plankton feeders. –AGF

  13. I was going to add some extra criticisms, such as phyto-plankton varying in size, mass, and probably optical properties, with varying CO2 concentrations. But there are already so many unanswered criticisms it hardly seems worth the time.

  14. Even if it were true there is a simple fix. Iron fertilization has been proven to dramatically increase phytoplankton production and biological activity. Anti life eco-fascists oppose an increase in food supply to the worlds creatures so this common sense solution has been blocked.

    • I was just reading about this. It would be costly and logistically unfeasible. Last-ditch measure.
      Anti life eco-fascists. That’s a new one for me, I think. Anti life?

      • There is a sub-set of environmentalists who would like to reduce the earth’s population of humans. A few have mentioned that as low as 100 million would be optimal.
        None of the alarmists have expressed any concern about the elderly who have died because they couldn’t afford to both heat their houses and eat.

      • “There is a sub-set of environmentalists who would like to reduce the earth’s population of humans. A few have mentioned that as low as 100 million would be optimal.”
        – What does that have to do with plankton?
        – I don’t know who you refer to. If one of them is Paul Ehrlich, I’ve no patience for treating his ideas from the 1970s as relevant today or reflective of any current ideas. So who says we should reduce the planet’s population to 100 million? Are they such a large and influential group that they are worth attention? Plenty of groups have radical ideas. So what?
        – There is also a subset of skeptics who assume that all scientists who think problems will arise from AGW are corrupt and/or dumb. I try to remember not all skeptics make such foolish assumptions; there are those who pursue truth.
        – Population increase is a problem for many reasons. Education, income and development are associated with birthrate declines,so they will come naturally at some point. Some people support advocacy and education to decrease birthrate, but this is tied to showing people the financial benefits of a small family – it’s not just an environmental matter, it’s a social and economic one.
        – There is still enough debate around the effectiveness, cost, and most importantly about the unforeseen consequences of adding iron to the ocean that it’s not appropriate to do so now. Does this opinion make me an anti-life eco-fascist?
        “None of the alarmists have expressed any concern about the elderly who have died because they couldn’t afford to both heat their houses and eat.”
        – I wasn’t aware that alarmists were obligated to share every concern with the public. Would that make you take them more seriously? What else would be necessary for you to be able to engage in discussion without making broad, erroneous assumptions about others’ ideas?

        • Kristi, John Holder, an Ehrlich associate and co-author, was Obama’s science advisor. Those views are still relevant, and still held by influential greens.

  15. 1% per year decline over 100 years would mean that phytoplankton is now about 1/3 of what it was in 1918. Should not such a drop be seen in krill and whales numbers and other sea life apart from fishing removals? Another 100 years and there will hardly be any phytoplankton at all. This is indeed an extraordinary claim. Its not just a big deal, its the biggest deal of all which would lead to the greatest of all extinctions probably including ourselves.

  16. Andy, presumably an increase in TSI (total solar irradiance), which occurred during the latter half of the period Boyce at al studied, could have sent main plankton activity to greater depths in the most recent portion of their time period. Also, the Secchi disk most certainly will have bigger error bars since the measurements depend on the visual acuity of the reader of th3 disk. For an ocean wide study of this kind, particularly using two differently designed instruments for parts of the study, error bars of greater than 20% should be expected. Now that they have redone the study changing annual mean decline from 1% to 0.23%/yr, it’s safe to say the change lacks significance. Correlation coefficient of 0.52 between methods speaks loudly.

    • Okay, since you begged for another 2 cents worth, wouldn’t higher CO2 tend to increase plankton photosynthesis and even some warming do the same? I’ve heard the story about low abundance of iron and calcium in seawater limiting growth, but as a geologist I don’t buy this. Oxidized sediments carrying abundant iron and calcium enter the sea carried by rivers, windblown dust, volcanic dust from land volcanoes and sub sea volcanoes and white and black seafloor “smokers”, meteoric dust, iron ships, billions of tons of iron ore a year , rusting cars, bridges, buildings…Solubilities of iron oxide and calcium carbonate are low to be sure, but when removed by plankton they are replaced by desolving more. We’ve learned that such creatures have the capability of changing pH locally.
      The Cretaceous White Cliffs of Dover are made entirely from the carbonate shells of coccolithiphores – skeletons of plankton – and the sea was warmer and had more abundant CO2 in the atmosphere. The climate had changed away beyond its temperature and CO2 regime of today. QED.

  17. Andy, thank you for going to so much effort and doing such a thorough job to SCIENTIFICALLY critique the literature on this subject, and PROVE that this subject, like EARTH’S CLIMATE SYSTEMS, ATMOSPHERIC OZONE, CORAL ETC, are NOT UNDERSTOOD YET, even remotely. I skipped straight to your conclusions because I knew they would be as you stated, and you BACKED UP YOUR CONCLUSIONS WITH A THOROUGH SCIENTIFIC INVESTIGATION OF WHAT IS IN THE SCIENTIFIC LITERATURE REGARDING PHYTOPLANKTON. THANK YOU:)))

  18. Thanks for this summary Andy!
    Well done.
    I am putting together a local talk on ocean acidification and how the biological pump has been able to fix increasing atmospheric carbon and pump it down to the oceans depths where it does not affect ecosystems for centuries and millennia. Most paper report increased phytoplankton and increased plankton deposits on the ocean floors. Only a few minority papers, specifically the Boyce paper, suggest phytoplankton declines but it is outweighed by evidence of increased photosynthesis around the world from other scientists resulting in increased pumping of CO2 to harmless depths.

  19. How did we get from cyanobacteria at the beginning of the discussion to red algae “. . .all contain plastids of the original red algae and are descended from it.” at the end of the discussion?

    • Sharp eye! But, cyanobacteria are an ancient form of phytoplankton. The sentence you refer to, says “modern phytoplankton” are descended from red algae, which is true. It is a little vague, but I think understandable. I could have written it better,

  20. another great wuwt essay,along with the recent essay by kip and work by willis it has been a great place to visit lately. it always is, but you know what i mean.
    one of the points andy raised that stuck out to me was the relatively shallow depths the study took place over .now unless there was very careful timing applied to all the measurements surely the diurnal cycle alone could cause massive swings in readings ?
    would the cpr data be subject to sample depth sensitivity of this nature? along with the fluctuation in phtyoplankton depth occurrence as a result of changing conditions, from seasonal variation to longer term changes.
    oh ,and a long shot. if anyone knows where i can find cpr data for calanus finmarchicus from the year 2000 until present day i would be eternally grateful. this species abundance is apparently closely correlated with the success or failure of many fish species in the north east and north west atlantic . the slight warming of the shelf waters around the uk and in particular the north sea is a reason i have read for the decline in this species in the area. i would like to know if the resurgence of cod, herring etc in recent years in the north sea is a result of an increase in calanus finmarchicus .

  21. If you look at all the fish skeletons on Google Earth you would think the problem was too much plankton production. I still have a Secchi Disk and never thought/taught that it would be usable for phytoplankton (even after the wonderful discovery of the tiny) except in offshore waters and where there was some kind of connection established. Similar estimates from satellites have also puzzled me, but never looked into the technical details. This measures chlorophyll which introduces the productivity/biomass difficulty present at all levels.
    Good article, too much to read, too little time. My small but over a long period experience with log stat uses, unless justified, is with papers trying to hide something.

  22. Andy – Very nice review! Well-written. You explain the biological background, have cool images of the organisms, cover the literature, and come to a great, reasoned conclusion! How I love to see people saying they don’t know – WE don’t know. There is much we don’t know, but on the other hand it’s absolutely extraordinary how much we are learning – it’s all a process, the accumulation of evidence in little bits and pieces that is usually so gradual that important breakthroughs may be recognized as such only years later. Even Boyce’s data could turn out to be an important part of the puzzle.
    I’ve heard that one threat to plankton is acidification. In fact, this is one of my own favorite little worries: what will happen if the plankton crash? If it were bad, it would be catastrophic for the oceanic food web, and affect the many many humans who get their protein from the sea. Researchers are concerned that they won’t be able to build and maintain their shells. One group has found in situ evidence of shell weakness that wasn’t present in the past (so to speak). If warn top water makes them go deeper that would affect their energy balance through decreased photosynthesis. The problem for shell-building may come from lack of materials or from the extra energy needed to move H+ up a steeper concentration gradient to the surrounding sea water
    pH has already been an economic problem:
    “By 2008, the oyster harvest at Whiskey Creek, a major Oregon supplier to the majority of West Coast oyster farmers, plummeted 80 percent….In fact, the chemistry of the ocean is changing at least 30 times faster than at any time during the 800,000 years prior to the industrial era.”
    http://c-can.info/2011/03/29/like-headlights-on-a-car/
    People are now breeding oysters tolerant of lower pH.
    The low pH that is a problem in the Pacific Northwest isn’t constant, it comes and goes, so they avoid the problem through monitoring. I read more about it awhile ago, have forgotten the details.

    • There has yet to be a measurable change in ocean pH.
      The problem the oyster men are having are they are in an area which has historically had huge swings in pH.
      All these little critters survived just fine with CO2 levels over 5000ppm. The tiny swings we are seeing now won’t impact them.

  23. Thank you for an interesting article, Andy. Given what we know of the trophic chains in the oceans, a large global decrease in phytoplankton is contrary to evidence.
    I think that the core of this controversy is not so much the Biology, but the carbon budget accounting. Carbon sinks have been a traditional source of [negative] surprises for the CO₂-hypothesis of global warming. From the “missing sink” of the 90’s, to the decrease in CO₂ airborne fraction with time. As every part of the CO₂-hypothesis must do its contribution to raise the level of alarm, specially after the Pause was identified, it became fashionable (i.e. good for publishing) to say that carbon sinks were about to saturate. For example Canadell et al., 2007 proposed that land sinks were approaching saturation, and Schuster et al., 2007 found that ocean sinks were saturating. In reality carbon sinks are accelerating (Keenan et al., 2016), as they have been doing since emissions started.
    It is within this context that the dispute about phytoplankton has to be viewed. Boyce et al., 2010 has already been incorporated to “common knowledge” despite being heavily contested within the field. NASA’s page about the carbon cycle states:
    “Warmer oceans—a product of the greenhouse effect—could also decrease the abundance of phytoplankton, which grow better in cool, nutrient-rich waters. This could limit the ocean’s ability to take carbon from the atmosphere through the fast carbon cycle.”
    https://earthobservatory.nasa.gov/Features/CarbonCycle/page5.php
    However the carbon cycle budget is just a fiction as well as the sea level rise budget. Just an accounting matching of numbers based on guessing, as our knowledge is insufficient to put real numbers there.
    For example in the budget, phytoplankton (as the main part of marine biota) hasn’t responded to the purported 2% increase in surface ocean carbon. Why would phytoplankton responded differently to land vegetation and not do its bit to reduce the airborne fraction? I can only guess that the rationale is that changes in temperature counteract the enhanced availability of CO₂. But this is difficult to believe, first because the changes in temperature for the 0-200 m ocean are much smaller than for land, and second because the changes in temperature for land have been positive for plants, not negative.
    https://scied.ucar.edu/sites/default/files/images/large_image_for_image_content/carbon_cycle_diagram_ipcc_900x543.jpg
    Carbon Cycle Diagram from the IPCC AR4
    https://scied.ucar.edu/imagecontent/carbon-cycle-diagram-ipcc
    As usual the climate wars are distorting every scientific field they touch.

  24. If phytoplankton was declining at an alarming rate, oxygen levels in the atmosphere would also be declining at an alarming rate. What more evidence is needed?

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