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Overview
Tiny Organisms Provide Power To Move Oceans
The microscopic plants that form the foundation of the ocean's food web are declining, reports a study published July 29 in Nature.
The tiny organisms, known as phytoplankton, also gobble up carbon dioxide to produce half the world's oxygen output—equaling that of trees and plants on land.
But their numbers have dwindled since the dawn of the 20th century, with unknown consequences for ocean ecosystems and the planet's carbon cycle.
Researchers at Canada's Dalhousie University say the global population of phytoplankton has fallen about 40 percent since 1950. That translates to an annual drop of about 1 percent of the average plankton population between 1899 and 2008.
The scientists believe that rising sea surface temperatures are to blame.
"It's very disturbing to think about the potential implications of a century-long decline of the base of the food chain," said lead author Daniel Boyce, a marine ecologist.
They include disruption to the marine food web and effects on the world's carbon cycle. In addition to consuming CO2, phytoplankton can influence how much heat is absorbed by the world's oceans, and some species emit sulfate molecules that promote cloud formation.
A continuing mystery story
"In some respect, these findings are the beginning of the story, not the end," Boyce said. "The first question is what will happen in the future. We looked at these trends over the past century but don't know what will happen 10 years down the road."
The study "makes a sorely needed contribution to our knowledge of historical changes in the ocean biosphere," said David Siegel of the University of California, Santa Barbara, and Bryan Franz of NASA in an essay, also published in Nature.
"Their identification of a connection between long-term global declines in phytoplankton biomass and increasing ocean temperatures does not portend well for [ocean] ecosystems in a world that is likely to be warmer," they wrote. "Phytoplankton productivity is the base of the food web, and all life in the sea depends on it."
Boyce said he and his co-authors began their study in an attempt to get a clearer picture of how phytoplankton were faring, given that earlier studies that relied on satellite measurements produced conflicting results.
Biggest declines at the poles
The scientists dug back into the historical record, well past 1997, the year continuous satellite measurements began. They examined a half-million data points collected using a tool called a Secchi disk, as well as measurements of chlorophyll—a pigment produced by the plankton.
The Secchi disk was developed in the 19th century by a Jesuit astronomer, Father Pietro Angelo Secchi, when the Papal navy asked him to map the transparency of the Mediterranean Sea.
What Secchi produced was a dinner plate-sized white disk that is lowered into ocean water until it cannot be seen anymore. The depth it reaches before disappearing gives a measure of water clarity.
That can be used as a proxy for phytoplankton population in a given area, since the tiny organisms live close to the ocean's surface, where they are exposed to sunlight they use to produce energy.
Data gathered with a Secchi disk are roughly as accurate as observations collected by satellites, Boyce said, although satellites have greater global reach.
The researchers found the most notable phytoplankton declines in waters near the poles and in the tropics, as well as the open ocean.
They believe that rising sea temperatures are driving the decline. As surface water warms, it tends to form a distinct layer that does not mix well with cooler, nutrient-rich water below, depriving phytoplankton of some of the materials they need to turn CO2 and sunlight into energy.
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49 Comments
Add CommentThe way I read this article they used a Secchi disk to compare a half million satellite points. If thats all they did then how did they determine plankton levels pre-satillite days, mathmatical interpretation won't do that. I find the Secchi disk to require a lot of personal interpretation because there are far more factors than just plankton affecting it's visibility. maybe the original report explains all that and this article is just way to abridged to convince me of it's decline. Is there a link to the original findings.
Reply | Report Abuse | Link to thisI tried the Nature article this is based on, but there's a paywall so couldn't find references or links available.
Reply | Report Abuse | Link to thisdrafter - They used Secchi disk records since the late 1800s until satellite measurements became available. In other words, they have satellite measurements since the 1990s and used recorded Secchi disk records to fill the gap back to the late 1800s. The article also stated that it has been shown that Secchi disk measurements are roughly as accurate as satellite measurements.
Reply | Report Abuse | Link to thisdrafter - They used Secchi disk records since the late 1800s until satellite measurements became available. In other words, they have satellite measurements since the 1990s and used recorded Secchi disk records to fill the gap back to the late 1800s. The article also stated that it has been shown that Secchi disk measurements are roughly as accurate as satellite measurements.
Reply | Report Abuse | Link to thisYou are not considering the impact of fishing.
Reply | Report Abuse | Link to thisPhytoplankton are eaten by other larger micro-organisms, which in turn are eaten by fish, which are eaten by larger fish. We take the large fish, the population of the small fish sky-rockets, they eat all the food available lower down the chain. Take out the top predator and everything down the food chain goes extinct - no population control.
Same rules apply to us. The bees are also going, whose going to fertilise every flower to get a grain of wheat or whatever.
There were times the oceans were warmer than now, and life on this planet was thriving, plentiful and evolving. Why is it more of a problem now, as it seems to be,
Reply | Report Abuse | Link to thisI'm a little skeptical of the proposed explanation. Ocean temperatures have risen by what, 1C? If the plankton are so delicately fine-tuned for a particular temperature, how come seasonal temperature variations don't wipe them out? And what happened to their population during other times of seasonal flux (e.g. the so-called "Little Ice Age"?)
Reply | Report Abuse | Link to thisCould it be something else that people are doing to the ocean (everyone's favorite Pacific garbage patch, or agricultural runoff) instead? Other poorly-understood ocean cycles?
(Not trying to grind an axe here; explanations as to why my understanding and instincts on the matter are wrong would be welcome.)
fffff, doesn't the 1 C rise refer to average ocean temperatures worldwide? So seasonal variations are subsumed within the average rise.
Reply | Report Abuse | Link to thisDidn't the Little Ice Age affect only the north Atlantic, the North Sea, and maybe the Baltic Sea and western continental Europe? Maybe plankton populations did drop in those areas then.
eogord, fffff - I'm also skeptical about ocean temperature being the principle cause here. While the average temperature may have risen slightly, that change probably doesn't approach the normal daily and seasonal variability around the Earth. Are there regular summertime plankton die-offs as a result of rising temperatures?
Reply | Report Abuse | Link to thisCuriously, the article states:
"Researchers at Canada's Dalhousie University say the global population of phytoplankton has fallen about 40 percent since 1950. That translates to an annual drop of about 1 percent of the average plankton population between 1899 and 2008."
By what method of 'translation' does a 40% population reduction since 1950 infer an annual drop of 'about 1 percent' since 1899 - straight line interpolation, rounded to the nearest percent annualized? Why not simply determine the actual population decline since 1899 from the data?
@jtdwyer
Reply | Report Abuse | Link to thisIf you have a 1% annual drop, you have the sequence 100%, 99%, 98.1%, 97.1% etc. So, even though you have a small, annual decline of 1%, over the years it builds up. If you do the math, the figures are quite right.
scientific earthling - so much wrong with that post- we dont need bees for most of the staple crops. we arent going to die out just because the bees die. same goes for fish. of course the small fish population would explode, but it would die down again and restabilise.
Reply | Report Abuse | Link to thisIt appears that there is only speculation and no actual data to support the conclusion that the drop is due to warmer oceans. The drop is alarming, but could easily be due to other human caused conditions unrelated to warming.
Reply | Report Abuse | Link to thisOceanic iron levels also play a huge role in aiding with the regulation of plankton populations, as iron is a critical marine micronutrient. Some have suggested ocean 'fertilizing,' whereby (excess) fixed iron is literally implanted onto the ocean surface in order to help reinvigorate plankton populations, but plankton blooms are a very likely result of such a move.
Reply | Report Abuse | Link to thisOcean temperature change on the minutest scale really is one of the most credible causes to dropping plankton populations (along with, as was mentioned before, overfishing of critical marine baitfish that feed on the larger zooplankton). Phyto and zooplankton thrive in cold salty water especially in higher latitudes since there salt water is closer to the surface allowing for viable photosynthesis, as is shown in this SEAWIFS image of global plankton distribution (red showing the highest concentrations).
http://www.nasaimages.org/luna/servlet/detail/NSVS~3~3~9486~109486:Decadal-Comparison-of-Plankton-Leve
While 1C degree change doesn't seem like much, it's important to remember the incredible heat capacity water (especially salt water) is known for. Of the two types of ocean water - high v. low salinity - saltier ocean water is denser and more capable of storing carbon, which the (primarily phyto) plankton then store. Anyone who has taken a basic physics course or waited for a pot of water to boil knows it takes a while for the water to actually heat up, and the ocean is no different. As the oceans warm, salt water sinks, leaving fresher (warmer) water behind. Also contributing to the influx of fresh water is melting ice sheets/glaciers and mountain snowmelt. All of this is undoubtedly plausible as a result of a 1C degree change and makes perfect sense. After all, would the same rate in temperature change in a human not warrant the same concern?
As for studying previous plankton population levels, geographers are able to accurately measure past plankton levels by studying thousands of different ocean cores taken off different shores from all around the world. Crustacean shells and fossilized plankton are a highly accurate indicator of paleoclimate regimes, historical nutrient levels, and O16/O18 ratios (used as a means of determining past precipitation temperatures), all of which are capable of measuring fluctuating marine plant, animal and plankton populations.
Is anybody else out there as horrified to hear about this as I am? Whatever the cause I am very, very worried. After all, those tiny little plankton are producing 50% of the oxygen you and I need to breathe.
Reply | Report Abuse | Link to thisI also think that when you are seeing a population crash, by the time you see 40% of the population gone, you are in the vertical part of the curve and the loss of the remaining 40% is due very quickly. I am looking to see the Nature article in full and to find out what that curve actually looks like if they published it.
As for iron being a critical nutrient for plankton, yes it is in some large areas of the oceans, but not all.
I guess I too am skeptical the root cause is global warming. I could buy the global warming explanation if the drop in plankton growth was limited to the tropics, but also in the polar regions? Have there already been major changes in the ocean currents due to global warming destroying currents that used to send nutrients into surface waters where plankton grow? Or are we looking at increases in strange toxins dumped into the oceans affecting plankton growth globally? We already see numerous large and spreading dead zones. Is there any linkage between dead zones and the global loss of plankton growth?
I dont think the populations of plankton will necessarily stabilize. In many cases where you see population crashes of 40% or more you see the species involved go extinct along with all the other species dependent on it.
Looking at the bees, will we as humans go extinct without bees? Our staple food crops rice, wheat, and corn do not need bee fertilization. But many of the other plants, responsible for producing all the other foods we eat and a lot of that other 50% of the oxygen we breathe, may all go extinct too if the bees go.
Does anyone at Scientific America have a degree a in Marine Sciences? I do and I could have saved you a lot of embarrassment before you posted this over dramatized article based on work done by some crack pots in the middle of no where Canada.
Reply | Report Abuse | Link to thisSechi Disk, is not a reliable or accurate instrument. More carbon in the marine system is good for them (until it changes the water PH too drastically), so is more light and other nutrients they need to replicate themselves.
Very misleading Scientific America. Very misleading.
They say the plankton are responsible for soaking up a lot of CO2 in the atmosphere. Is anyone else concerned about the implications of a positive feedback loop of the CO2 build-up that is acidifying the oceans?
Reply | Report Abuse | Link to thisJT, and others,
Reply | Report Abuse | Link to thisI was going to say what Dimitris said, but he beat me to it.
I had similar thoughts with regard to the sensitivity of phytoplankton to temperature, but here is a synopsis.
http://dalnews.dal.ca/2010/07/28/photoplank.html
A warmer surface layer reduces the amount of turnover, and with reduced turnover come less nutrients.
Dimitris, Chris G - Sorry, but if the net decrease in phytoplankton populations in the 60 years since 1950 is 40% (as estimated by this crew), no matter how you figure it, the annualized reduction is less than 1%. Of course, you could round 0.0666~% up to 1%, but that would be extremely sloppy. I hate math, but if I calculate correctly a 1% annual reduction compounded over 60 years produces a 55% net reduction, not the stated 40% net reduction.
Reply | Report Abuse | Link to thisI don't know why they derive the (1% annual) decrease since 1899 from the estimate for the period of 1950-2008 rather than rely on their data.
Sorry, Chris G, but your link didn't provide any access to data, and I won't be paying $32 to access the Nature article, thank you. Perhaps it's all just a misunderstanding that the data would immediately clarify...
They do seem to be a swell bunch of folks, though.
What is the temperature variability throughout the world's oceans throughout the year? What's this variability's impact on phytoplankton population? Is a 1C degree average ocean temperature increase truly significant, or do local seasonal variations render this change insignificant? If so there must be some other explanation for the reported phytoplankton population decrease, which this study seems to assert has now reached nearly 100% in the past 110 years!!!
Perhaps I just misunderstand.
Sorry I hate math: they could have rounded 0.6667% up to 1%...
Reply | Report Abuse | Link to thisThere seems to be a great deal of confusion between seasonal, and indeed diurnal temperature range and 'climate'. The literature is full of examples of habitat boundaries changing as a result of less than one degree of climate change. One dramatically illustrated terrestrial example can be found at the website of the National Arbor Day Foundation
Reply | Report Abuse | Link to thishttp://www.arborday.org/media/mapchanges.cfm
Mean temperatures in the US have risen only marginally in the past 20 years, but the Northward movement of 'hardiness' zones for trees in line with climate change has been profound, despite the fact that these same trees cope with annual temperature ranges in excess of 30 degrees Celsius. The difference is the plants have adapted to cope with certain levels and durations of frost. Climate changes affect the overall length and timing of critical growing conditions.
Climate change in Australia has been much more significant, with >20% change in rainfall patterns and between 1 and 2.5 degrees of mean temperature rise. Winemakers here move their harvest date to coincide with the optimum development of grapes, sugar levels, etc. The 'harvest date' has been moved forward 30 days in the last 30 years!
watson - Thanks for the additional insight. I think no one can reasonably deny that global warming has and will have negative impact on floral populations. However, it's difficult to isolate the effect of a specific variable, such as increasing temperatures in a range of seasonal temperature variations, from other factors, such as predator population variations, environmental toxins and in the case of generally stationary terrestrial species, encroachment by humans.
Reply | Report Abuse | Link to thisIn the case of highly mobile populations of plankton, the article states:
"The scientists dug back into the historical record, well past 1997, the year continuous satellite measurements began. They examined a half-million data points collected using a tool called a Secchi disk, as well as measurements of chlorophylla pigment produced by the plankton."
"That can be used as a proxy for phytoplankton population in a given area, since the tiny organisms live close to the ocean's surface, where they are exposed to sunlight they use to produce energy."
The Secchi disk cannot distinguish between species of plankton or even other potential contributing factors to decreased local water visibility. Ancient sporadic samplings
of plankton populations that are highly mobile and locally variable due to many factors other than temperature change may provide indecisive evidence of variation due to annual average temperature changes. There are some valid reasons to question the methods and conclusions of this study in addition to the mathematical veracity of this report.
Just in case anyone missed it, if, as asserted in this study, the phytoplankton population has decreased by 1% annually for the past 109 years, there would be no phytoplankton population to be concerned about, since it would have become extinct already!!!!
Reply | Report Abuse | Link to thisAs far as agricultural runoff goes, this usually is a problem of "Causing" algal blooms due to high phosphate/fertilizer levels. does anyone know if algal populations are considered synonymous to phytoplankton? also, the runoff question is partly addressed when they say that all the areas that are not close to shore are showing this decrease.
Reply | Report Abuse | Link to thisI am interested in more information about this story. the non-mixing of water for instance means that while the oceans are increasing in temperature, perhaps the surface is getting even more warm than the 1 degree...
As far as agricultural runoff goes, this usually is a problem of "Causing" algal blooms due to high phosphate/fertilizer levels. does anyone know if algal populations are considered synonymous to phytoplankton? also, the runoff question is partly addressed when they say that all the areas that are not close to shore are showing this decrease.
Reply | Report Abuse | Link to thisI am interested in more information about this story. the non-mixing of water for instance means that while the oceans are increasing in temperature, perhaps the surface is getting even more warm than the 1 degree...
JT,
Reply | Report Abuse | Link to thisOK, I will show you the math.
A 1% reduction per year is the same as saying that every year has 99% of whatever the previous year had. From there it is simple.
0.99 ^ 60 = 0.547
Hmm, that would be about a 45.3% reduction.
Let's try
0.9912 ^ 58 = 0.5989
That's pretty close to a 40% reduction (1 - 0.5989 = 0.4011).
So, it looks like they rounded an annual decline of around 0.0088 to "about 1 percent".
It's not clear in the passage near this how the 1899 year factors in, but that is likely an issue with the write-up of this article rather than the original from which it is derived.
Why 58? Because the year 2008 was mentioned in a context that would indicate it was the last year for which data was collected. 2008-1950=58. By the time you do the write-up, submit for publication, and your paper goes through the review process; this sounds about the right amount of time for publication now.
Reply | Report Abuse | Link to thisNot to be derogatory JT, but if you are struggling with the math, what good is the data going to do you?
JT,
Reply | Report Abuse | Link to thisOK, I will show you the math.
A 1% reduction per year is the same as saying that every year has 99% of whatever the previous year had. From there it is simple.
0.99 ^ 60 = 0.547
Hmm, that would be about a 45.3% reduction.
Let's try
0.9912 ^ 58 = 0.5989
That's pretty close to a 40% reduction (1 - 0.5989 = 0.4011).
So, it looks like they rounded an annual decline of around 0.0088 to "about 1 percent".
It's not clear in the passage near this how the 1899 year factors in, but that is likely an issue with the write-up of this article rather than the original from which it is derived.
Ender beat me to my main comment (and a great summary by danniiikkaa), secchi disks are a pretty subjective means of measurement, ("I don't think I can see it anymore, how about you Mikey?") but the best part of this article is the mention that "secchi disks are as roughly accurate as satellite observations" and that "... researchers found the most notable phytoplankton declines in waters near the poles and in the tropics, as well as the open ocean."
Reply | Report Abuse | Link to this1) While satellite data has been verified by discrete measurements in many areas of the ocean, it is notoriously inaccurate in other areas such as along coastlines, the poles, and the Southern Ocean. This is due to a number of factors, including refraction from other particles in the water such riverine discharge (DOM, silicates), cloud cover, pass angle of the satellite, and accumulated spatial and temporal coverage (SeaWiFS especially is very biased to the northern hemisphere). These factors lead to an over or underestimate in chl-a, which can be a big issue when you're trying to calculate phytoplankton abundance, growth rate, and productivity. So yeah... satellite data can be just about as accurate as secchi disks.
2) These areas that they claim to have a decrease in phytoplankton numbers relate to "problem areas" in remote satellite sensing. Add in the fact the many open oceans are oligotrophic (meaning there's not a lot of primary productivity at the best of times) and I'm starting to get a wee bit skeptical on their conclusions.
3) Chlorophyll-a is just a proxy (and not the greatest proxy) for phytoplankton abundance... it does not sufficiently predict productivity (how much CO2 the phytoplankton are taking up) or growth rate on it's own.
4) They're just taking into account surface chl-a, studies have definitely shown that there are max chl-a values at depth (40-70 m in some cases) where phytoplankton thrive. It's very dependent on time of year and location, but surface chl-a values can vastly underestimate numbers and thus productivity.
Behrenfeld 1997 has a great overview on the limitations of satellite data as well as the follies of relying on chl-a for taking into account CO2 uptake and bloom dynamics.
I'm definitely a bit skeptical about this study and will have to find the real paper. In the meantime, I think the shift in the ocean's carbonate system is a much greater concern for phytoplankton than sea temperature changes.
*4) surface chl-a values can vastly underestimate total numbers throughout the water column
Reply | Report Abuse | Link to thisGreat Kate, I'm sure these researchers and their audience, the people who actually have a subscription to Nature, including other marine specialists, are unaware of the limitations of the disks and that is how this bit of shoddy work got published in one of the most well-regarded journals in the world. Thanks.
Reply | Report Abuse | Link to thisYou are countering a number of claims that I don't see being made.
Let us know when/where your research indicating that phytoplankton has not declined gets published.
Chris G: Do you work for Scientific American? Are you upset that I expressed professional criticism on a study that was paraphrased for the general public? I've read the actual paper in Nature because I do have a subscription and I will say first off that they could hire better writers to summarise the research.
Reply | Report Abuse | Link to thisThat being said, I am a researcher within the marine sciences and my research deals with phytoplankton uptake of CO2. I know first hand, not only by reading papers from the experts of the field, but by actually encountering issues within my research concerning the limitations of chl-a as a proxy for phytoplankton biomass as well as the verification of satellite data, hence why I shared my view.
But I could be a crackpot in front of a laptop for all you know, it doesn't really matter, so here's my main point. The likes of the "big" journals like Science and Nature often pick papers that are a) topical to global problems and b) are compilations of a large scale of work that are summarised for the general science audience. Most of the papers in these big journals would be the amalgamation of several papers for more specific journals. The point is that thousands of papers get submitted to these big journals and many get denied because they are too specific, but us scientists know that by possibly getting published in these types of journals our research gets wide recognition which leads to more discussion but also, more grant money!
But discussion is the main point... yes these papers go through rigorous review processes before print, but the reason that we scientists have journals and not publish all of our findings in the likes of Scientific American is that criticism and discussion are important building blocks for the progression of science and discovery.
Many people have the stereotype that science is all about feuding Tesla vs. Edison style, but if I met these researchers at a conference I would say the exact same thing I posted above, in which case we'd discuss their research (probably over a beer) and they'd try to convince me why their research is accurate. I would say that climate change over the past century probably does have an effect on phytoplankton population, but if they use a shoddy technique for doing so I'll call them out for it, as will the scientific community. But this leads to someone else saying "hey, that's a good idea, but I can do it better." And what better start for doing so than a Nature publication?
What are you thoughts Chris? Do you have a scientific view?
ChrisG: Also, be sure to send me your email address, because I'm publishing a paper on the verification and application of SeaWiFS and HICO chl-a values with in situ values sometime in the next few months, it probably isn't big enough for the likes of Nature, but I'm sure Marine Chemistry will give me a chance
Reply | Report Abuse | Link to thisLast one everyone... but in the comments section of the ACTUAL Nature paper, there is discussion and criticism (shock!horror!) concerning the authors' choice of sampling areas and data reduction: (Copy and pasted from Nature)
Reply | Report Abuse | Link to thisSteve Short says: In my view, it is highly unlikely this supposed trend is a valid finding for the following reasons:
(1) Much of the global 'standing crop' of cyanobacteria are to be found around the continental shelves where the supplies of critical nutrients such as nitrogen, iron and silica are to be found in greatest abundance. The waters off Eastern Patagonia are a well known textbook example of this where airborne dust from the Andean volcanos and glacial moraine runoff combines to increase the rate of nutrient export into that coastal shelf area. The study does not appear to have considered the very important coastal shelf regions at all.Yet ironically those are the very regions where the oceans have received, in recent centuries, the greatest input (and an increasing one) of such nutrients due to the expansion of the human race, much of which is concentrated around the continental margins and in great archipelagos such as Japan, Indonesia, the Phillipines etc.
2) It is well known from numerous sea-based microcosm experiments that cyanobacterial primary productivity rises with increasing partial pressure of CO2 (just as it does with increasing levels of key nutrients). It is highly likely that this effect far outweighs any temperature-based effect. Indeed I have shown on the Niche Modeling blog from satellite based sensing data (MODIS AQUA etc) that the NH oceans contain two great consortia of cyanobacteria which bloom in two different temperature bands of the annual cycle whereas the SH ocean has only one such consortium. Despite this, it is also possible to show that the rate at which the surface partial pressure of CO2 lags behind the global mean partial pressure over the Great Southern Ocean (SO) below 40 S has been actually slowly increasing since ~1980 not decreasing. This can only mean that the cyanobacterial primary productivity of the SO is increasing with increasing global partial pressure of CO2.
http://landshape.org/enm/oceanic-cayanobacteria-in-the-modern-global-cycle/
(Cont)
Reply | Report Abuse | Link to this(3) It is only in the last few decades that we have even approached a mature understanding of the major speciation of cyanobacterial species in the ocean and hence their often differing consortial/ecological relationships to 'traditional' gross parameters such as transparency and chlorophyll-a. Just a few decades ago, if one was to assert that seawater typically contained ~100,000 cells/mL of the picocyanobacterium Prochlorococcus and ~10,000 cells/mL of the 'normal' cyanobacterium Synecchococcus one would have been laughed at quite simply because few were aware the major species Prochlorococcus was even present!
Regrettably, I fear this is just yet another one of those naively earnest Nature papers which easily reveals its post-modernist origins in the current, globally dominant, socio-political movement of our times.
Chris G - I do hate math, but Excel delivers the series:
Reply | Report Abuse | Link to this100 99 98.01 97.0299 96.059601 95.09900499 94.14801494 93.20653479 92.27446944 91.35172475 90.4382075 89.53382543 88.63848717 87.7521023 86.87458128 86.00583546 85.14577711 84.29431934 83.45137615 82.61686238 81.79069376 80.97278682 80.16305895 79.36142836 78.56781408 77.78213594 77.00431458 76.23427143 75.47192872 74.71720943 73.97003734 73.23033697 72.4980336 71.77305326 71.05532273 70.3447695 69.6413218 68.94490859 68.2554595 67.57290491
66.89717586 66.2282041 65.56592206 64.91026284 64.26116021 63.61854861 62.98236312 62.35253949 61.72901409 61.11172395 60.50060671 59.89560065 59.29664464 58.70367819 58.11664141 57.535475 56.96012025 56.39051905 55.82661385 55.26834772
I'm sure I can rely on you to resolve this discrepancy.
Reply | Report Abuse | Link to thisLet's come to grips with losing a significant amount of a global source of oxygen over a short time period. In 2004 about half of the world's atmospheric oxygen was estimated to come from phytoplankton. Monitors of atmospheric oxygen have shown a slow steady decline over recent decades. We have a margin of safety , but we are within a few percentage points of the minimal oxygen needs for human species and other mammals and birds.
We humans don't/didn't control the causes of phytoplankton decline, regardless of what the causes are or how many causes there are.
But as a species, we passed "Peak Water" in the late 1980s. Peak Oxygen could be, well, it could be a real killer.
There is also the aspect of ocean acidification to consider. Our oceans are becoming rich in carbonic acid which is known to inversely effect plankton levels.The acidification, along with temperature increases could be contributing to phytoplankton declines.
Reply | Report Abuse | Link to thisAre there any calculations regarding the impact of increased UV upon phytoplankton populations?
Reply | Report Abuse | Link to thisMonday
Reply | Report Abuse | Link to thisAugust 9, 2010
First let me explain the numbers. If you have a drop of 40% in phytoplankton over 60 years you have 60% of the phytoplankton left. If you assume there is a constant percentage drop over the years rather than a constant quantity lost, you look first for the 60th root of 0.6. It looks like this on your calculator
0.6 ^(1/60) = 0.6 ^ 0.0166666666667 = 0.99152237902841734629062574836806
So that gives a yearly decrease of 1 - 0.99152237902841734629062574836806 =
0.00847762097158265370937425163194 =
or 0.8478 % which they rounded off to about 1%.
And a constant percentage decrease of 1% per year over 109 years leaves a level at 33.4% of the original level after 109 years. .99 ^109 = .334
I just read one of the SciAm articles that explains why global warming and increased sea surface temperatures lead to a decrease in phytoplankton besides just a limitation of mixing and decreased nutrients.
You can see the article at http://www.scientificamerican.com/article.cfm?id=how-will-warmer-oceans-affect-sea-life
Plankton consists basically of two types, phytoplankton, the green and blue green algae, mostly single cells, and the zooplankton, the small animals that eat the phytoplankton and each other.
There may be other effects besides just warmer water involved , too, such as toxins which kill phytoplankton or slow phytoplankton growth, and perhaps over fishing has some effects too. Unfortunately, increasing carbon dioxide levels may actually decrease the amount of carbon dioxide absorbed in the oceans as diatoms have a harder time making calcium carbonate in an ocean with a lower pH and higher carbon dioxide levels. This calcium carbonate may be a large component of the carbon dioxide uptake of the oceans.
Apparently, when the sea surface temperature warms slightly the phytoplankton grow faster but the zooplankton eat much faster which reduces the total amount of phytoplankton.
When the fish population is reduced, the predators that eat the zooplankton are reduced so there is more zooplankton available to eat the phytoplankton.
You can look at it like this. The phytoplankton are the primary producers like the rice, wheat, trees, grasses and bushes of the oceans. The zooplanktons are herbivores like the goats, deer, cows, sheep, elephants, and mice of the oceans. The fish are the wolves, foxes, and lions of the oceans. When you eliminate all the predators, the herbivores go crazy and eat all the vegetation eliminating it and end up starving to death.
That is a little simplistic but an easy way to visualize the interaction of the species.
What may happen is that the area, if high in nutrients with low mixing currents, grows phytoplankton fast enough to produce a eutrophic dead zone with seriously low oxygen levels in the waters and lots of hydrogen sulfide produced. If low in nutrients, it may produce an area with just very low phytoplankton growth.
I think, although I havent seen any marine biologists propounding this theory, the loss of the primary predatory fish, and I am including the fish down to the size of anchovies not just the larger fish, increases the number, size, and persistence of dead zones. The primary predatory fish swim into areas of high productivity, eat there and swim out exporting the nutrients into areas of the oceans with lower productivity.
guido - Very well done. Presuming the methodology you suggest (there's no counter evidence, anyway), their estimation of the change over 109 years includes a rounding error factor of nearly 16%. Personally, I hate math, but I'd expect precise mathematicians to object to such sloppy methods.
Reply | Report Abuse | Link to thisMoreover, the sporadic and inconsistent sampling of historical ocean visibility leads to the obvious question of how such assessments were normalized for entire oceans? These methods of evaluating historical global plankton populations appear to me to be highly inaccurate.
Please look again at KateJo83's comments on August 5 about science. Even flawed data can provide insights that lead to better data collection and analysis.
Reply | Report Abuse | Link to thisI haven't gone over the data myself, but I need to point out that with your estimate of 16% rounding error (and I haven't checked that out either) we could bracket the Nature article's report of a loss of 40% with your rounding error, and still see a shocking rate of loss of capacity in the planetary oxygen cycle.
If a human patient lost between 12% and 28% of lung capacity, within a relatively brief period of time, it would be cause for intense scrutiny and a course of action.
In this time of climate instability and intense resource demands, oxygen has been taken for granted. Check out publications by Ralph Keeling and others to better understand the sinks/sources of O2 and the trends.
TreeDiversity - "My" estimate was simply derived from guido's analysis of the method used to determine the annual change in phytoplankton population since 1899; "0.8478 % which they rounded off to about 1%." The error estimate was mathematically determined to be 1% - 0.8478% = about 16%.
Reply | Report Abuse | Link to thisStill hating math, I realized I should have determined the percentage of rounding as (1-0.8478)/08478 - nearly an 18% rounding error factor.
At any rate, I question this method of estimation, which I consider to be:
A. Determine the current global phytoplankton population (unspecified) based on satellite data.
B. Determine a proxy 1950 global phytoplankton population from sporadic Secchi disk samples taken somewhere around the globe.
C. The net change in phytoplankton population since 1950 = A-B = -40%.
D. The annual change since 1950 = -40% / (2008-1950) = 0.8478 % ~ 1%.
E. The net change since 1899 = (2009-1899) * 1% = 33.4%.
Check my representation of guido's methodology - it seems absurdly sloppy.
The weakest assumption, though, is that some number of sporadic Secchi disk estimates of phytoplankton population from ocean water visibility depth taken somewhere around the globe at some periods of time can be used to determine a proxy global phytoplankton population estimate.
I'm sure these issues would be resolved if we only shelled out $32 to read the research paper, aren't you? However, given the information available to me from this article I have little confidence in the methods described.
OK, OK, so there's still some errors in the damned math. I hate math and I happen to have been suffering from uncorrectable double vision for the past week: you kids do your own damned math.
Reply | Report Abuse | Link to thisForget the math, the main issue is the global extrapolations made from rudimentary samplings of not even plankton populations but ocean visibility!
I can tell you that in my living room its a nice and comfortable 71F degrees - do you conclude there's no global warming?
I don't deny that there are likely significant impacts to critical phytoplankton populations that have occurred globally since human industrialization, but this report reads like play science - if you accept its conclusions you are a naive, innocent child.
Wednesday
Reply | Report Abuse | Link to thisAugust 11. 2010
I was not trying to use the 1% figure to try and make a prediction of what the levels of the phytoplankton would be in 2069. I was using 109 years to point out that a constant percentage decline per year yielded much different results from a decline of a constant amount per year.
And if you do the math correctly
[(1-0.008478)^109] - [ (1-.01)^109]
you will find a difference between a 1% constant percentage decrease and a 0.8478% constant percentage decrease at about 6% not 16% after 109 years.
However this is a very rough, off the cuff estimate of what the numbers would look like then as I havent seen the numbers published in Nature yet as I am not working in the field, etc, etc.
I would not want to make any numerical estimate without looking at the published numbers and doing some more sophisticated curve fitting which I cant because I dont have the relevant curve fitting software up on this computer, my last one having been stolen along with the disks for the software and I dont even know if they make a version of the software I like that is compatible with this computer, excuse, excuse, excuse. If you want better numbers put your money where your questions are and give me a grant to do the curve fitting, etc., etc., and what do you expect for free even on a science blog?
guido - Thanks the help, despite all (LOL) - would a $2 grant help? On second thought, I don't really want any more numbers...
Reply | Report Abuse | Link to thisstevenstarr
Reply | Report Abuse | Link to thisSeveral researchers tackled UV and phytoplankton in the early 1990s (google scholar can find you some free .pdfs).
The Boyce et al data base on phytoplankton volume (the subject of the current review) might help further a global quantitative assessment.
Boyce and fellow researchers found the strongest correlation with phytoplankton decline globally to be sea surface temperatures (SST).
Reply | Report Abuse | Link to thisFiguring out what might drive the rest of the variability in phytoplankton (with UV-B and or acidification among the suspects) becomes more do-able research after land mark work like this one. The decline in phytoplankton in the Arctic, despite warming, would be an interesting place to to look at UV-B, as the loss of the ozone layer is more pronounced at the poles.
Boyce et al. is six page article and was well worth the bike ride to the local university to read it.
TreeDiversity - Sounds like a wonderful study. Can you by chance comment on how sporadic historical Secchi disk samples were used to produce a normalized proxy for annual global phytoplankton populations? Thanks.
Reply | Report Abuse | Link to thisRayleigh scattering is less now than it was during the last ice age. Rayleight scattering reduces sunlight and so it causes global cooling. Rayleigh scattering increases as the square of molecular polarizability, and so oxygen causes most Rayleigh scattering in the atmosphere. Oxygen concentration in the atmosphere is less now than during the last ice age, probably due to plankton change in the oceans. For example, a one percent increase in oxygen concentration in the atmosphere could lower Earths temperature by three degrees. As oceans warm, plankton will once again increase in concentration causing oxygen to increase back to a normal level, and return the Earth to its normal ice age state.
Reply | Report Abuse | Link to thisHopefully, if humans can burn enough fossil fuels, we can prevent oxygen from increasing in concentration, and thus we can prevent an ice age.