World Library  
Flag as Inappropriate
Email this Article

Iron fertilization

Article Id: WHEBN0004145551
Reproduction Date:

Title: Iron fertilization  
Author: World Heritage Encyclopedia
Language: English
Subject: Climate engineering, Phytoplankton, Plankton, Algal bloom, Bio-geoengineering
Collection: Aquatic Ecology, Geoengineering, Planetary Engineering
Publisher: World Heritage Encyclopedia

Iron fertilization

An oceanic phytoplankton bloom in the South Atlantic Ocean, off the coast of Argentina covering an area about 300 miles (480 km) by 50 miles

Iron fertilization is the intentional introduction of iron to the upper ocean to stimulate a phytoplankton bloom. This is intended to enhance biological productivity, which can benefit the marine food chain and is under investigation in hopes of increasing carbon dioxide removal from the atmosphere. Iron is a trace element necessary for photosynthesis in all plants. It is highly insoluble in sea water and is often the limiting nutrient for phytoplankton growth. Large algal blooms can be created by supplying iron to iron-deficient ocean waters.

A number of ocean labs, scientists and businesses are exploring fertilization as a means to sequester atmospheric carbon dioxide in the deep ocean, and to increase marine biological productivity which is likely in decline as a result of climate change. Since 1993, thirteen international research teams have completed ocean trials demonstrating that phytoplankton blooms can be stimulated by iron addition.[1] However, controversy remains over the effectiveness of atmospheric CO
sequestration and ecological effects.[2] The most recent open ocean trials of ocean iron fertilization were in 2009 (January to March) in the South Atlantic by project Lohafex, and in July 2012 in the North Pacific off the coast of British Columbia, Canada, by the Haida Salmon Restoration Corporation (HSRC).[3]

Fertilization also occurs naturally when upwellings bring nutrient-rich water to the surface, as occurs when ocean currents meet an ocean bank or a sea mount. This form of fertilization produces the world's largest marine habitats. Fertilization can also occur when weather carries wind blown dust long distances over the ocean, or iron-rich minerals are carried into the ocean by glaciers,[4] rivers and icebergs.[5]


  • History 1
  • Experiments 2
  • Science 3
    • Role of iron 3.1
    • Volcanic ash as a source of iron 3.2
    • Carbon sequestration 3.3
      • Analysis and quantification 3.3.1
    • Dimethyl sulfide and clouds 3.4
  • Financial opportunities 4
  • Multilateral reaction 5
  • Sequestration definitions 6
  • Debate 7
    • Precautionary principle 7.1
    • 20th-century phytoplankton decline 7.2
    • Comparison to prior phytoplankton cycles 7.3
    • Sequestration efficiency 7.4
    • Ecological issues 7.5
      • Algal blooms 7.5.1
      • Deep water oxygen levels 7.5.2
      • Ecosystem effects 7.5.3
    • Conclusion and further research 7.6
  • See also 8
  • References 9
    • Changing ocean processes 9.1
    • Micronutrient iron and ocean productivity 9.2
    • Ocean biomass carbon sequestration 9.3
    • Ocean carbon cycle modeling 9.4
  • Further reading 10
    • Technique 10.1
    • Context 10.2
    • Debate 10.3


Consideration of iron's importance to phytoplankton growth and photosynthesis dates back to the 1930s when English biologist Joseph Hart speculated that the ocean's great "desolate zones" (areas apparently rich in nutrients, but lacking in plankton activity or other sea life) might simply be iron deficient.[6] Little further scientific discussion of this issue was recorded until the 1980s, when oceanographer John Martin renewed controversy on the topic with his marine water nutrient analyses. His studies indicated it was indeed a scarcity of iron micronutrients that was limiting phytoplankton growth and overall productivity in these "desolate" regions, which came to be called "High Nutrient, Low Chlorophyll" (HNLC) zones.[6]

In an article in the scientific journal Nature (February 1988; 331 (6157): 570ff.), John Gribbin was the first scientist to publicly suggest that the upcoming greenhouse effect might be reduced by adding large amounts of soluble iron compounds to the oceans of the world as a fertilizer for the aquatic plants.

Martin's famous 1988 quip four months later at Woods Hole Oceanographic Institution, "Give me a half a tanker of iron and I will give you another ice age",[6][7] drove a decade of research whose findings suggested that iron deficiency was not merely impacting ocean ecosystems, it also offered a key to mitigating climate change as well.

Perhaps the most dramatic support for Martin's hypothesis was seen in the aftermath of the 1991 eruption of Mount Pinatubo in the Philippines. Environmental scientist Andrew Watson analyzed global data from that eruption and calculated that it deposited approximately 40,000 tons of iron dust into the oceans worldwide. This single fertilization event generated an easily observed global decline in atmospheric CO
and a parallel pulsed increase in oxygen levels.[8]


Martin hypothesized that increasing phytoplankton photosynthesis could slow or even reverse global warming by sequestering enormous volumes of CO
in the sea. He died shortly thereafter during preparations for Ironex I,[9] a proof of concept research voyage, which was successfully carried out near the Galapagos Islands in 1993 by his colleagues at Moss Landing Marine Laboratories.[6] Since then 9 international ocean studies have examined the fertilization effects of iron:

  • LOHAFEX (Indian and German Iron Fertilization Experiment), 2009 [26][27][28] Despite widespread opposition to LOHAFEX, on 26 January 2009 the German Federal Ministry of Education and Research (BMBF) gave clearance for this fertilization experiment to commence. The experiment was carried out in waters low in silicic acid which is likely to affect the efficacy of carbon sequestration.[29] A 900 square kilometers (350 sq mi) portion of the southwest Atlantic Ocean was fertilized with iron sulfate. A large phytoplankton bloom was triggered, however this bloom did not contain diatoms because the fertilized location was already depleted in silicic acid, an essential nutrient for diatom growth.[29] In the absence of diatoms, a relatively small amount of carbon was sequestered, because other phytoplankton are vulnerable to predation by zooplankton and do not sink rapidly upon death.[29] These poor sequestration results have caused some to suggest that ocean iron fertilization is not an effective carbon mitigation strategy in general. However, prior ocean fertilization experiments in high silica locations have observed much higher carbon sequestration rates because of diatom growth. LOHAFEX has just confirmed that the carbon sequestration potential depends strongly upon careful choice of location.[29]
  • Convention on Biological Diversity (CBD) and the London convention on the dumping of wastes at sea which according to them contain moratoriums on geoengineering experiments.[30][31] On 15 July 2014, all gathered scientific data was made available to the public to support further scientific research.[32]


The maximum possible result from iron fertilization, assuming the most favourable conditions and disregarding practical considerations, is 0.29W/m2 of globally averaged negative forcing,[33] which is almost sufficient to reverse the warming effect of about 1/6 of current levels of anthropogenic CO
emissions. It is notable, however, that the addition of silicic acid or choosing the proper location could, at least theoretically, eliminate and exceed all man-made CO

Role of iron

About 70% of the world's surface is covered in oceans, and the upper part of these (where light can penetrate) is inhabited by algae. In some oceans, the growth and reproduction of these algae is limited by the amount of iron in the seawater. Iron is a vital micronutrient for phytoplankton growth and photosynthesis that has historically been delivered to the pelagic sea by dust storms from arid lands. This Aeolian dust contains 3–5% iron and its deposition has fallen nearly 25% in recent decades.[34]

The Redfield ratio describes the relative atomic concentrations of critical nutrients in plankton biomass and is conventionally written "106 C: 16 N: 1 P." This expresses the fact that one atom of phosphorus and 16 of nitrogen are required to "fix" 106 carbon atoms (or 106 molecules of CO
). Recent research has expanded this constant to "106 C: 16 N: 1 P: .001 Fe" signifying that in iron deficient conditions each atom of iron can fix 106,000 atoms of carbon,[35] or on a mass basis, each kilogram of iron can fix 83,000 kg of carbon dioxide. The 2004 EIFEX experiment reported a carbon dioxide to iron export ratio of nearly 3000 to 1. The atomic ratio would be approximately: "3000 C: 58,000 N: 3,600 P: 1 Fe".[36]

Therefore small amounts of iron (measured by mass parts per trillion) in "desolate" HNLC zones can trigger large phytoplankton blooms. Recent marine trials suggest that one kilogram of fine iron particles may generate well over 100,000 kilograms of plankton biomass. The size of the iron particles is critical, however, and particles of 0.5–1 micrometer or less seem to be ideal both in terms of sink rate and bioavailability. Particles this small are not only easier for cyanobacteria and other phytoplankton to incorporate, the churning of surface waters keeps them in the euphotic or sunlit biologically active depths without sinking for long periods of time.

Volcanic ash as a source of iron

Large amounts of eolian (wind deposited) sediment are deposited annually in the world’s oceans. These deposits have long been thought to be the main source of iron to the surface ocean, and therefore the main source of iron for biological productivity. Recent studies suggest that volcanic ash has a significant role in supplying the world’s oceans with iron as well.[37] Volcanic ash is composed of glass shards, pyrogenic minerals, lithic particles, and other forms of ash which release nutrients at different rates depending on structure and the type of reaction caused by contact with water.[38]

Murray et al. recently assessed the relationship between increases of biogenic opal in the sediment record with increased iron accumulation over the last million years.[39] In August 2008, an eruption in the Aleutian Islands, Alaska deposited ash in the nutrient-limited Northeast Pacific. There is strong evidence that this ash and iron deposition resulted in one of the largest phytoplankton blooms observed in the subarctic.[40]

Carbon sequestration

Air-sea exchange of CO

Previous instances of biological carbon sequestration have triggered major climatic changes in which the temperature of the planet was lowered, such as the

  • Oschlies, A., W. Koeve, W. Rickels, and K. Rehdanz (2010). "Side effects and accounting aspects of hypothetical large-scale southern ocean iron fertilization". Biogeosciences Discuss. 7 (2): 2949–2995.  
  • The Iron Shore Of Science Journalism
  • An Open Letter to the Marine Science Community: Has Personal Bias Derailed Science?
  • Canadian Fishing at the Grand Banks, Zebra Mussels,and Iron's Effect on Plankton: an example of plausible connections -Chris Yukna (Ecole des Mines, France)
  • Basu, Sourish (September 2007). "Oceangoing Iron: A venture to profit from a C02-eating algae bloom riles scientists". Scientific American 297 (4) (Scientific American, Inc., published October 2007). pp. 23–24. Retrieved 2008-08-04.  Note: Only first two paragraphs are available free on-line


  • Global Impact of Ocean Nourishment - I.S.F. Jones, Berkeley
  • Fertilizing the Ocean with Iron - First article in a six-part series from Woods Hole Oceanographic Institution's Oceanus magazine


  • Ocean Gardening Using Iron Fertilizer
  • Iron 'Fertilization' Causes Plankton Bloom - National Science Foundation
  • Ocean Carbon Sequestration Abstracts - US Department of Energy
  • After the SOIREE: Testing the Limits of Iron Fertilization - NASA
  • The Geritol Effect - University of Southern California
  • Seeds of Iron to Mitigate Climate Change-
  • Dumping Iron - Wired News


Montreal, Technical Series No. 45, 53 pagesScientific Synthesis of the Impacts of Ocean Fertilization on Marine Biodiversity.Secretariat of the Convention on Biological Diversity (2009).

Further reading

  • Andrew Watson, James Orr (2003). "5. Carbon Dioxide Fluxes in the Global Ocean". In Fasham, M. J. R. Ocean Biogeochemistry. Berlin: Springer.  
  • J.L. Sarmiento and J.C. Orr (December 1991). "Three-Dimensional Simulations of the Impact of Southern Ocean Nutrient Depletion on Atmospheric CO2 and Ocean Chemistry". Limnology and Oceanography 36 (8): 1928–50.  

Ocean carbon cycle modeling

  • J.A. Raven and  
  • Jefferson T. Turner (February 2002). "Zooplankton Fecal Pellets, Marine Snow and Sinking Phytoplankton Blooms". Aquatic Microbial Ecology 27 (1): 57–102.  
  • Paul Falkowski, et al. (2003). "4. Phytoplankton and Their Role in Primary, New and Export Production". In Fasham, M. J. R. Ocean Biogeochemistry. Berlin: Springer.  
  • Markels, M and R T Barber (2001). "Proc 1st Nat. Conf. on Carbon Sequestration". Washington, DC. 

Ocean biomass carbon sequestration

  • Open Ocean Iron Fertilization for Scientific Study and Carbon Sequestration - K. Coale, 2001.
  • Ocean Fertilisation - V. Smetecek, 2004.
  • by Ocean Fertilization2Sequestration of CO - M. Markels and R. Barber, 2001.
  • Effect of In-Situ Fertilization on Phytoplankton Growth and Biological Carbon Fixation In the Ocean - T. Yoshimura and D. Tsumune, 2005.
  • Stimulating the Ocean Biological Carbon Pump by Iron Fertilization - Jun Nishioka, 2003.
  • Iron Fertilization of the Oceans: Reconciliing Commercial Claims with Published Models - P. Lam & S. Chisholm, 2002.
  • Coale KH, Johnson KS, Fitzwater SE, et al. (October 1996). "A massive phytoplankton bloom induced by an ecosystem-scale iron fertilization experiment in the equatorial Pacific Ocean". Nature 383 (6600): 495–501.  
  • Schiermeier Q (April 2004). "Iron seeding creates fleeting carbon sink in Southern Ocean". Nature 428 (6985): 788.  
  • Victor Smetecek (March 1999). "Diatoms and the Ocean Carbon Cycle". Protist 150 (1): 25–32.  
  • Kent Cavender-Bares, et al. (March 1999). "Differential Response of Equatorial Pacific Phytoplankton to Iron Fertilization". Limnology and Oceanography 44 (2): 237–246.  

Micronutrient iron and ocean productivity

  • Global Change and Oceanic Primary Productivity: Effects of Ocean-Atmosphere-Biological Feedbacks - A. J. Miller et al., 2003.
  • Sequestration2The Processes of the Ocean's Biological Pump and CO - Jun Nishioka, 2002.

Changing ocean processes

  1. ^ Boyd, P.W., et al.; Jickells, T; Law, CS; Blain, S; Boyle, EA; Buesseler, KO; Coale, KH; Cullen, JJ; De Baar, HJ; Follows, M; Harvey, M.; Lancelot, C.; Levasseur, M.; Owens, N. P. J.; Pollard, R.; Rivkin, R. B.; Sarmiento, J.; Schoemann, V.; Smetacek, V.; Takeda, S.; Tsuda, A.; Turner, S.; Watson, A. J. (2007). "Mesoscale Iron Enrichment Experiments 1993-2005: Synthesis and Future Directions". Science 315 (5812): 612–7.  
  2. ^ Buesseler, K.O., et al.; Doney, SC; Karl, DM; Boyd, PW; Caldeira, K; Chai, F; Coale, KH; De Baar, HJ; Falkowski, PG; Johnson, KS; Lampitt, R. S.; Michaels, A. F.; Naqvi, S. W. A.; Smetacek, V.; Takeda, S.; Watson, A. J. (2008). "ENVIRONMENT: Ocean Iron Fertilization—Moving Forward in a Sea of Uncertainty". Science 319 (5860): 162.  
  3. ^ Tollefson, Jeff (2012-10-25). "Ocean-fertilization project off Canada sparks furore". Nature 490 (7421): 458–459.  
  4. ^  
  5. ^ "Cold Carbon Sink: Slowing Global Warming with Antarctic Iron - SPIEGEL ONLINE". 2008-12-18. Retrieved 2012-04-17. 
  6. ^ a b c d Weier, John. "John Martin (1935-1993)". On the Shoulders of Giants.  
  7. ^ "Ocean Iron Fertilization – Why Dump Iron into the Ocean". Café Thorium.  
  8. ^ Watson, A.J. (1997-02-13). , ocean productivity and climate"2"Volcanic iron, CO (PDF). Nature 385 (6617): 587–588.  
  9. ^ Ironex (Iron Experiment) I
  10. ^ Ironex II, 1995
  11. ^ SOIREE (Southern Ocean Iron Release Experiment), 1999
  12. ^ EisenEx (Iron Experiment), 2000
  13. ^ SEEDS (Subarctic Pacific Iron Experiment for Ecosystem Dynamics Study), 2001
  14. ^ SOFeX (Southern Ocean Iron Experiments - North & South), 2002
  15. ^ a b "Effects of Ocean Fertilization with Iron To Remove Carbon Dioxide from the Atmosphere Reported" (Press release). Retrieved 2007-03-31. 
  16. ^ SERIES (Subarctic Ecosystem Response to Iron Enrichment Study), 2002
  17. ^ SEEDS-II, 2004
  18. ^ EIFEX (European Iron Fertilization Experiment), 2004
  19. ^ Smetacek, Victor; Christine Klaas, Volker H. Strass, Philipp Assmy, Marina Montresor, Boris Cisewski, Nicolas Savoye, Adrian Webb, Francesco d’Ovidio, Jesús M. Arrieta, Ulrich Bathmann, Richard Bellerby, Gry Mine Berg, Peter Croot, Santiago Gonzalez, Joachim Henjes, Gerhard J. Herndl, Linn J. Hoffmann, Harry Leach, Martin Losch, Matthew M. Mills, Craig Neill, Ilka Peeken, Rüdiger Röttgers, Oliver Sachs, et al. (18 July 2012). "Deep carbon export from a Southern Ocean iron-fertilized diatom bloom" (Abstract).  
  20. ^ David Biello (July 18, 2012). "Controversial Spewed Iron Experiment Succeeds as Carbon Sink". Scientific American. Retrieved July 19, 2012. 
  21. ^ Field test stashes climate-warming carbon in deep ocean; Strategically dumping metal puts greenhouse gas away, possibly for good July 18th, 2012 Science News
  22. ^ CROZEX (CROZet natural iron bloom and Export experiment), 2005
  23. ^ Scientists to fight global warming with plankton 2007-05-21
  24. ^ Planktos kills iron fertilization project due to environmental opposition 2008-02-19
  25. ^ Venture to Use Sea to Fight Warming Runs Out of Cash New York Times 2008-02-14
  26. ^ "LOHAFEX: An Indo-German iron fertilization experiment". Retrieved 2012-04-17. 
  27. ^ Bhattacharya, Amit (2009-01-06). "Tossing iron powder into ocean to fight global warming". The Times Of India. 
  28. ^ Climate fix' ship sets sail with plan to dump iron - environment - 09 January 2009"'". New Scientist. Retrieved 2012-04-17. 
  29. ^ a b c d "Lohafex provides new insights on plankton ecology". Retrieved 2012-04-17. 
  30. ^ Martin Lukacs (October 15, 2012). "World's biggest geoengineering experiment 'violates' UN rules: Controversial US businessman's iron fertilisation off west coast of Canada contravenes two UN conventions". The Guardian. Retrieved October 16, 2012. 
  31. ^ Henry Fountain (October 18, 2012). "A Rogue Climate Experiment Outrages Scientists". The New York Times. Retrieved October 19, 2012. 
  32. ^
  33. ^ Lenton, T. M., Vaughan, N. E. (2009). "The radiative forcing potential of different climate geoengineering options". Atmos. Chem. Phys. Discuss. 9: 2559–2608.  
  34. ^ a b Ocean Plant Life Slows Down and Absorbs less Carbon NASA Earth Observatory
  35. ^ Sunda, W. G., and S. A. Huntsman (1995). "Iron uptake and growth limitation in oceanic and coastal phytoplankton". Mar. Chem. 50: 189–206.  
  36. ^ de Baar H . J. W., Gerringa, L. J. A., Laan, P., Timmermans, K. R (2008). "Efficiency of carbon removal per added iron in ocean iron fertilization". Mar Ecol Prog Ser. 364: 269–282.  
  37. ^ Duggen, S. et al. 2007. Subduction zone volcanic ash can fertilize the surface ocean and stimulate phytoplankton growth: Evidence from biogeochemical experiments and satellite data. Geophysical Research Letters, Vol. 34.
  38. ^ Olgun, N. et al. 2011. Surface Ocean Iron Fertilization: The role of airborne volcanic ash from subduction zone and hot spot volcanoes and related iron fluxes into the Pacific Ocean. Global Biogeochemical Cycles, Vol. 25.
  39. ^ Murray, Richard W., Margaret Leinen and Christopher W. Knowlton. 2012. Links between iron input and opal deposition in the Pleistocene equatorial Pacific Ocean. Nature Geoscience 5: 270–274.
  40. ^ Hemme, R. et al. 2010. Volcanic ash fuels anomalous plankton bloom in subarctic northeast Pacific. Geophysical Research Letters, Vol. 37.
  41. ^ Video of extremely heavy amounts of "marine snow" in the Charlie-Gibbs Fracture Zone in the Mid-Atlantic Ridge. Michael Vecchione, NOAA Fisheries Systematics Lab. Published at Census of Marine Life website
  42. ^ Schiermeier Q (January 2003). "Climate change: The oresmen". Nature 421 (6919): 109–10.  
  43. ^ a b Charlson, R. J.,  
  44. ^ Lovelock, J.E. (2000) [1979]. Gaia: A New Look at Life on Earth (3rd ed.). Oxford University Press.  
  45. ^ Wingenter, Oliver W.; Karl B. Haase, Peter Strutton, Gernot Friederich, Simone Meinardi, Donald R. Blake and  
  46. ^ Australia2Feb 2007 Carbon Update, CO
  47. ^ the Ocean, Scienceline
  48. ^ Russia sets minimum carbon offset price
  49. ^ Plankton Found to Absorb Less Carbon Dioxide BBC, 8/30/06
  50. ^ Recruiting Plankton to Fight Global Warming, New York Times, Business Section, page 1, 5/1/07
  51. ^ Iron fertilisation sunk as an ocean carbon storage solution University of Sydney press release 12 December 2012 and Harrison, D P IJGW (2013)
  52. ^ RESOLUTION LC-LP.1 (2008) ON THE REGULATION OF OCEAN FERTILIZATION. London Dumping Convention. 31 October 2008. Retrieved 9 August 2012. 
  53. ^ "Assessment Framework for scientific research involving ocean fertilization agreed".  
  54. ^ Gregg WW, Conkright ME, O'Reilly JE, et al. (March 2002). "NOAA-NASA Coastal Zone Color Scanner reanalysis effort". Appl Opt 41 (9): 1615–28.  
  55. ^ (Antoine et al.., 2005)
  56. ^ Gregg et al.. 2005
  57. ^ Basgall, Monte (2004-02-13). "Goal of ocean 'iron fertilization' said still unproved". Retrieved 2006-11-27. 
  58. ^ "The Sietch Blog » Ocean Iron Fertilization In Southern Ocean Fails To Capture Significant Carbon". Retrieved 2012-04-17. 
  59. ^ Tricka, Charles G., Brian D. Bill, William P. Cochlan, Mark L. Wells, Vera L. Trainer, and Lisa D. Pickell (2010). "Iron enrichment stimulates toxic diatom production in high-nitrate, low-chlorophyll areas".  
  60. ^ Parsons, T.R.; Lalli, C.M. (2002). "Jellyfish Population Explosions:Revisiting a Hypothesis of Possible Causes". La Mer 40: 111–121. Retrieved July 20, 2012. 
  61. ^ Trick, Charles G.; Brian D. Billb,c, William P. Cochlanb, Mark L. Wellsd, Vera L. Trainerc, and Lisa D. Pickelld (2010). "Iron enrichment stimulates toxic diatom production in high-nitrate, low-chlorophyll areas". Proceedings of the National Academy of Sciences of the United States of America 107 (13): 5887–5892.  
  62. ^ Buesseler, KO; Doney, SC; Karl, DM; Boyd, PW; Caldeira, K; Chai, F; Coale, KH; de Baar, HJ; Falkowski, PG; Johnson, KS; Lampitt, RS; Michaels, AF; Naqvi, SW; Smetacek, V; Takeda, S; and Watson, AJ (11 January 2008). "Ocean Iron Fertilization -- Moving Forward in a Sea of Uncertainty". Science 319 (5860): 162.  


See also

premature to sell carbon offsets from the first generation of commercial-scale OIF experiments unless there is better demonstration that OIF effectively removes CO2, retains that carbon in the ocean for a quantifiable amount of time, and has acceptable and predictable environmental impacts.[62]
in 2008 maintained that it would be ScienceA statement published in

Critics and advocates generally agree that most questions on the impact, safety and efficacy of ocean iron fertilization can only be answered by much larger studies.

Conclusion and further research

However, CO
-induced surface water heating and rising carbonic acidity are already shifting population distributions for phytoplankton, zooplankton and many other creatures. Optimal fertilization could potentially help restore lost/threatened ecosystem services.

Depending upon the composition and timing of delivery, iron infusions could preferentially favor certain species and alter surface ecosystems to unknown effect. Population explosions of jellyfish, that disturb the food chain impacting whale populations or fisheries is unlikely as iron fertilization experiments that are conducted in high-nutrient, low-chlorophyll waters favor the growth of larger diatoms over small flagellates. This has been shown to lead to increased abundance of fish and whales over jellyfish[60] A 2010 study shows that iron enrichment stimulates toxic diatom production in high-nitrate, low-chlorophyll areas [61] which, the authors argue, raises "serious concerns over the net benefit and sustainability of large-scale iron fertilizations".

Ecosystem effects

The largest plankton replenishment projects under consideration are less than 10% the size of most natural wind-fed blooms. In the wake of major dust storms, natural blooms have been studied since the beginning of the 20th century and no such deep water dieoffs have been reported.

When organic bloom detritus sinks into the abyss, a significant fraction will be devoured by anoxic and threaten other benthic species.However this would entail the removal of oxygen from thousands of cubic km of benthic water beneath a bloom and so this seems unlikely.

Deep water oxygen levels

A 2010 study of iron fertilization in an oceanic high-nitrate, low-chlorophyll environment, however, found that fertilized Pseudo-nitzschia diatom spp., which are generally nontoxic in the open ocean, began producing toxic levels of domoic acid. Even short-lived blooms containing such toxins could have detrimental effects on marine food webs.[59]

Most species of phytoplankton are harmless or beneficial, given that they constitute the base of the marine food chain. Fertilization increases phytoplankton only in the deep oceans (far from shore) where iron deficiency is the problem. Most coastal waters are replete with iron and adding more has no useful effect.

Critics are concerned that fertilization will create harmful algal blooms (HAB). The species that respond most strongly to fertilization vary by location and other factors and could possibly include species that cause red tides and other toxic phenomena. These factors affect only near-shore waters, although they show that increased phytoplankton populations are not universally benign.

A "red tide" off the coast of La Jolla, San Diego, California.

Algal blooms

Ecological issues

Current estimates of the amount of iron required to restore all the lost plankton and sequester 3 gigatons/year of CO
range widely, from approximately 2 hundred thousand tons/year to over 4 million tons/year. The latter scenario involves 16 supertanker loads of iron and a projected cost of approximately €20 billion ($27 billion).

Some ocean trials reported positive results. IronEx II reported conversion of 1,000 kilograms (2,200 lb) to carbonaceous biomass equivalent to one hundred full-grown redwoods within two weeks. Eifex recorded fixation ratios of nearly 300,000 to 1.

  1. Data: none of the ocean trials had enough boat time to monitor their blooms for more than five weeks, confining their measurements to that period. Blooms generally last 60–90 days with the heaviest "precipitation" occurring during the last two months.
  2. Scale: most trials used less than 1,000 kilograms (2,200 lb) of iron and thus created small blooms that were quickly devoured by opportunistic zooplankton, krill, and fish that swarmed into the seeded region.

The counter-argument to this is that the low sequestration estimates that emerged from some ocean trials are largely due to these factors:

Fertilization may sequester too little carbon per bloom, supporting the food chain rather than raining on the ocean floor, and thus require too many seeding voyages to be practical.[15][57] A 2009 Indo-German team of scientists examined the potential of the south-western Atlantic to sequester significant amounts of carbon dioxide, but found few positive results.[58]

Sequestration efficiency

Fertilization advocates respond that similar algal blooms have occurred naturally for millions of years with no observed ill effects. The Azolla event occurred around 49 million years ago and accomplished what fertilization is intended to achieve (but on a larger scale).

Comparison to prior phytoplankton cycles

While advocates argue that iron addition would help to reverse a supposed decline in phytoplankton, this decline may not be real. One study reported a decline in ocean productivity comparing the 1979–1986 and 1997–2000 periods,[54] but two others found increases in phytoplankton.[55][56]

20th-century phytoplankton decline

The argument can be applied in reverse, by considering emissions to be the action and remediation an attempt to partially offset the damage.

The precautionary principle (PP) states that if an action or policy has a suspected risk of causing harm, in the absence of scientific consensus, the burden of proof that it is not harmful falls on those who would take the action. The side effects of large-scale iron fertilization are not yet known. Creating phytoplankton blooms in naturally iron-poor areas of the ocean is like watering the desert: in effect it changes one type of ecosystem into another.

Precautionary principle

While ocean iron fertilization could represent a potent means to slow global warming current debate raises a variety of concerns.


Advocates argue that modern climate scientists and Kyoto Protocol policy makers define sequestration in much shorter time frames. For example, they recognize trees and grasslands as important carbon sinks. Forest biomass only sequesters carbon for decades, but carbon that sinks below the marine thermocline (100–200 meters) is effectively removed from the atmosphere for hundreds of years, whether it is remineralized or not. Since deep ocean currents take so long to resurface, their carbon content is effectively sequestered by the criterion in use today.

Carbon is not considered "sequestered" unless it settles to the ocean floor where it may remain for millions of years. Most of the carbon that sinks beneath plankton blooms is dissolved and remineralized well above the seafloor and will eventually (days to centuries) return to the atmosphere, negating the original effect.

Sequestration definitions

An Assessment Framework for Scientific Research Involving Ocean Fertilization, regulating the dumping of wastes at sea (labeled LC-LP.2(2010)) was adopted by the Contracting Parties to the Convention in October 2010 (LC 32/LP 5).[53]

The parties to the London Dumping Convention adopted a non-binding resolution in 2008 on fertilization (labeled LC-LP.1(2008)). The resolution states that ocean fertilization activities, other than legitimate scientific research, "should be considered as contrary to the aims of the Convention and Protocol and do not currently qualify for any exemption from the definition of dumping".[52]

Multilateral reaction

Since the advent of the Kyoto Protocol, several countries and the European Union have established carbon offset markets which trade certified emission reduction credits (CERs) and other types of carbon credit instruments internationally. In 2007 CERs sold for approximately €15–20/ton CO
.[46] Iron fertilization is relatively inexpensive compared to scrubbing, direct injection and other industrial approaches, and can theoretically sequester for less than €5/ton CO
, creating a substantial return.[47] In August, 2010, Russia established a minimum price of €10/ton for offsets to reduce uncertainty for offset providers.[48] Scientists have reported a minimum 6–12% decline in global plankton production since 1980,[34][49] A full-scale international plankton restoration program could regenerate approximately 3–5 billion tons of sequestration capacity worth €50-100 billion in carbon offset value. Given this potential return on investment, carbon traders and offset customers are watching the progress of this technology with interest.[50] However, a recent study indicates the cost versus benefits of iron fertilization puts it behind carbon capture and storage and carbon taxes.[51]

Financial opportunities

During the Southern Ocean Iron Enrichment Experiments (SOFeX), DMS concentrations increased by a factor of four inside the fertilized patch. Widescale iron fertilization of the Southern Ocean could lead to significant sulfur-triggered cooling in addition to that due to the increased CO
uptake and that due to the ocean's albedo increase, however the amount of cooling by this particular effect is very uncertain.[45]

Some species of plankton produce dimethyl sulfide (DMS), a portion of which enters the atmosphere where it is oxidized by hydroxyl radicals (OH), atomic chlorine (Cl) and bromine monoxide (BrO) to form sulfate particles, and potentially increase the cloud cover. This may increase the albedo of the planet and so cause cooling - this proposed mechanism is central to the CLAW hypothesis.[43] This is one of the examples used by James Lovelock to illustrate his Gaia hypothesis.[44]

Schematic diagram of the CLAW hypothesis (Charlson et al., 1987)[43]

Dimethyl sulfide and clouds

The potential of iron fertilization as a atmosphere amounting to about 0.8 to 1.4 gigatonnes of carbon per year.[42] This quantity is comparable in magnitude to annual anthropogenic fossil fuels combustion of approximately 6 gigatonnes. It should be noted that the Antarctic circumpolar current region is only one of several in which iron fertilization could be conducted—the Galapagos islands area being another potentially suitable location.

Evaluation of the biological effects and verification of the amount of carbon actually sequestered by any particular bloom requires a variety of measurements, including a combination of ship-borne and remote sampling, submarine filtration traps, tracking buoy spectroscopy and satellite telemetry. Unpredictable ocean currents have been known to remove experimental iron patches from the pelagic zone, invalidating the experiment.

Analysis and quantification

Of the carbon-rich biomass generated by plankton blooms, half (or more) is generally consumed by grazing organisms (zooplankton, krill, small fish, etc.) but 20 to 30% sinks below 200 meters (660 ft) into the colder water strata below the thermocline. Much of this fixed carbon continues falling into the abyss, but a substantial percentage is redissolved and remineralized. At this depth, however, this carbon is now suspended in deep currents and effectively isolated from the atmosphere for centuries. (The surface to benthic cycling time for the ocean is approximately 4,000 years.)


This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.

Copyright © World Library Foundation. All rights reserved. eBooks from World eBook Library are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.