'Iron fertilization' is the intentional introduction of
iron to the upper
ocean to increase the marine
food chain and to sequester
carbon dioxide from the atmosphere
[1]. It involves encouraging the growth of marine
phytoplankton blooms by physically distributing microscopic iron particles in otherwise nutrient rich, but iron deficient blue ocean waters. An increasing number of ocean labs, scientists and businesses are exploring it as a means to revive declining plankton populations, restore healthy levels of
marine productivity and/or
sequester millions of tons of CO
2 to slow down
global warming. Since 1993, ten international research teams have completed relatively small-scale ocean trials demonstrating the effect.
History
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.
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 micronutrient that was limiting phytoplankton growth and overall productivity in these "desolate" regions, which came to be called "High Nutrient, Low Chlorophyll" (
HNLC) zones.
[2]
Martin's famous 1991 quip at
Woods Hole Oceanographic Institution, "Give me a half a tanker of iron and I will give you another ice age"
[3], 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. Martin hypothesized that increasing phytoplankton photosynthesis could slow or even reverse global warming by sequestering enormous volumes of CO
2 in the sea. He died shortly thereafter during preparations for Ironex I
[4], 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. Since then 9 other international ocean trials have confirmed the iron fertilization effect:
★ Ironex II , 1995
[5]
★ SOIREE (Southern Ocean Iron Release Experiment), 1999
[6]
★ EisenEx (Iron Experiment), 2000
[7]
★ SEEDS (Subarctic Pacific Iron Experiment for Ecosystem Dynamics Study), 2001
[8]
★ SOFeX (Southern Ocean Iron Experiments - North & South), 2002
[9][10]
★ SERIES (Subarctic Ecosystem Response to Iron Enrichment Study), 2002
[11]
★ SEEDS-II, 2004
[12]
★ EIFEX (European Iron Fertilization Experiment), 2004
[13]
★ CROZEX (CROZet natural iron bloom and Export experiment), 2005
[14]
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
2 and a parallel pulsed increase in oxygen levels.
[15]
Science
The 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/or 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 wind-driven dust storms from arid lands. This
Aeolian dust contains 3~5% iron and its deposition has fallen nearly 25% in recent decades
[16] due to modern changes in land use and agricultural practices as well as increased greening of dry regions thanks to increasing levels of atmospheric CO
2. (Arid zone grasses and vegetation now lose less water vapor through their stomata to absorb the same amount of carbon dioxide, and thus stay greener longer, reducing dust storm frequency and the amount of iron reaching the deep seas. Increasing sand desertification does little to compensate for this shortfall since sand is primarily silica with relatively low iron content.)
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
2). 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
[17], 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 fixation ratio of nearly 300,000 to 1. Assuming that data is on a mass basis, then the normalized atomic ratio would be approximately: "380,000 C: 58,000 N: 3,600 P: 1 Fe".
In "desolate" HNLC zones, therefore, small amounts of iron (measured by mass parts per trillion) delivered by either by the wind or a planned restoration program can trigger large responsive 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 micrometre 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.
Carbon sequestration
Plankton that generate calcium or silica
carbonate skeletons, such as
diatoms,
coccolithophores and
foraminifera, account for most direct carbon sequestration. When these organisms die their carbonate skeletons sink relatively quickly and form a major component of the carbon-rich deep sea precipitation known as
marine snow. Marine snow also includes fish fecal pellets and other organic detritus, and can be seen steadily falling thousands of meters below active plankton blooms
[18].
Of the carbon-rich biomass generated by natural plankton blooms and fertilization events, half or more is generally consumed by grazing organisms (
zooplankton,
krill, small fish, etc.) but 20 to 30% sinks below 200 meters into the colder water strata below the
thermocline. Much of this fixed carbon continues falling into the abyss as marine snow, 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 or more. (The surface to
benthic depths cycling time for the entire ocean system is approximately 4000 years.)
Analysis and quantification: Evaluation of the biological effects and verification of the amount of carbon actually sequestered by any particular bloom requires a variety of sophisticated measurements. Methods currently in use include a combination of ship-borne and remote sampling, submarine filtration traps, tracking buoy
spectroscopy, and
satellite telemetry.
Dimethyl sulfide and clouds
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 ultimately clouds. This may increase the
albedo of the planet and so cause cooling.
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
2 uptake and that due to the ocean's albedo increase, however the amount of cooling by this particular effect is very uncertain.
[19]
Financial opportunities
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 sell for approximately €15~20/ton CO
2e and European analysts project these prices will nearly double by 2012
[20].
Since NASA scientists have reported a minimum 6~9% decline in global plankton production since 1980
[16] (and other scientists report 10~12% losses
[22]), this suggests that a full-scale international plankton restoration program could regenerate approximately 3~5 billion tons of carbon sequestration capacity worth €75 billion or more in carbon offset value. Iron fertilization is a relatively inexpensive
carbon sequestration technology compared to
scrubbing,
direct injection and other industrial approaches, and can theoretically generate these credits for less than €5/ton CO
2e.
[23]. Given this potential return on investment, some carbon traders and offset customers are watching the progress of this technology with interest
[24].
Debate
While many advocates of ocean iron fertilization see it as modern society's last best hope to slow global warming long enough to change our consumption patterns and energy systems, a number of critics have also arisen including some academics,
deep greens and proponents of competing technologies who cite a variety of concerns.
Precautionary Principle
Critics: We don’t know the possible side-effects of large scale iron fertilization. Not enough research has been done. We should not risk iron fertilization on the scale needed to affect global CO2 levels or animal populations. Creating blooms in naturally iron-poor areas of the ocean is like watering the desert; you're completely changing one type of ecosystem into another. Advocates argue that iron addition would help to reverse a supposed decline in phytoplankton, but this decline may not be real. While one study (Gregg and Conkright, 2002) reported a decline in ocean productivity between the period 1979-1986 and 1997-2000, another study (Antoine et al, 2005) found a 22% increase between 1979-1986 and 1998-2002. Gregg et al 2005 also reported a recent increase in phytoplankton.
Advocates: Similar blooms have occurred naturally for millions of years with no observed ill effects.
Not even trying to remedy these industrial impacts is far more irresponsible considering the known pace of increasing harm.
Inadequacies
According to certain ocean iron fertilization trial reports, this approach may actually sequester very little carbon per bloom, with most of the plankton being eaten rather than deposited on the ocean floor, and thus require too many seeding voyages to be practical.
[25]
The counter-argument to this is that the low sequestration estimates that emerged from some ocean trials are largely due to three factors:
#Timing: none of the ocean trials had enough boat time to monitor their blooms for more than 27 days, and all their measurements are confined to those early weeks. Blooms generally last 60~90 days with the heaviest precipitation occurring during the last two months.
#Scale: most trials used less than 1000 kg of iron and thus created small blooms that were quickly devoured by opportunistic
zooplankton,
krill and fish that swarmed into the seeded region.
#Academic conservatism: having an obviously limited data set and unique sequestration criteria (see Sequestration Definitions below), many peer-reviewed ocean researchers are understandably reluctant to project or speculate upon the results their experiments might have actually achieved during the full course of a bloom.
Some ocean trials did indeed report remarkable results. According to IronEx II reports, their thousand kilogram iron contribution to the equatorial Pacific generated a carbonaceous
biomass equivalent to one hundred full-grown
redwoods within the first two weeks. Researchers on Wegener Institute's 2004 Eifex experiment recorded carbon dioxide to iron fixation ratios of nearly 300,000 to 1.
Current estimates of the amount of iron required to restore all the lost plankton and sequester 3
gigatons/year of CO
2 range widely, from approximately two hundred thousand tons/year to over 4 million tons/year. Even in the latter worst case scenario, this only represents about 16
supertanker loads of iron and a projected cost of less than €20 billion (
$27 Billion). Considering EU penalties for Kyoto non-compliance will reach €100/ton CO
2e (
$135/ton CO
2e) in 2010 and the annual value of the global carbon credit market is projected to exceed €1 trillion by 2012, even the most conservative estimate still portrays a very feasible and inexpensive strategy to offset half of all industrial emissions.
Sequestration definitions
Critics: In ocean science, carbon is not considered removed from the system unless it settles to the ocean floor where it is truly sequestered for eons. Most of the organic and inorganic carbon that sinks beneath plankton blooms is dissolved and remineralized at great depths and will eventually be re-released to the atmosphere, negating the original effect.
Advocates: Ocean science does traditionally define "sequestration" in terms of sea floor sediment that is isolated from the atmosphere for millions of years. Modern climate scientists and
Kyoto Protocol policy makers, however, define sequestration in much shorter time frames and recognize trees and even 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 or thousands of years, whether it is remineralized or not. Since deep ocean currents take so long to resurface, their carbon content is effectively "sequestered" by any terrestrial criterion in use today.
Ecological issues
Harmful Algal Blooms (HAB)
Critics: Some plankton species cause
red tides and other toxic phenomena. How do we know what kind of plankton will bloom in these events? What will prevent toxic species from poisoning
lagoons,
tide pools and other sensitive ecosystems along our coasts?
Advocates: Most species of phytoplankton are entirely harmless, and indeed beneficial. Red tides and other harmful algal blooms are largely coastal phenomena and primarily affect creatures that eat contaminated coastal shellfish. Iron stimulated plankton blooms only work in the deep oceans where iron deficiency is the problem. Most coastal waters are replete with iron and adding more has no effect. Since all phytoplankton blooms last only 90~120 days at most, in the open ocean fertilized patches of any species will dissipate long before reaching any land.
Deep water oxygen depletion
Critics: When organic bloom detritus sinks into the abyss, a significant fraction will be devoured by
bacteria, other microorganisms and deep sea animals which also consume oxygen. A large bloom could, therefore, render certain regions of the sea deep beneath it anoxic and threaten other
benthic species.
Advocates: The largest plankton replenishment projects now being proposed are less than 10% the size of most natural wind-fed blooms. In the wake of major dust storms, many extremely vast natural blooms have been studied since the beginning of the 20th century and no such deep water dieoffs have ever been reported.
Ecosystem alterations
Critics: Depending upon the composition and timing of delivery, these iron infusions could preferentially favor certain species and alter surface ecosystems to unknown effect. Population explosions of
jellyfish, disturbance of the food chain with a huge impact on
whale populations or fisheries are cited as potential dangers.
Advocates: CO
2-induced surface water heating and rising carbonic acidity are already shifting population distributions for phytoplankton, zooplankton and many other creatures on a massive scale.
If certain infusions or space/time coordinates do show asymmetrical selective impacts in certain regions, the effect is inherently constrained by the limited size and 90-day lifespan of each bloom. Only larger scale research will show if this is really a problem, what factors tilt the playing field, and/or whether this issue can be effectively addressed.
Conclusion and further research
Advocates say that using this technique to restore ocean plankton to recent known levels of health would help solve half the climate change problem, revive major fisheries and
cetacean populations, and alleviate several other urgent ocean crises. Critics say global warming must be solved at the source, large scale iron fertilization experiments have never been attempted, the effects could be inadequate, and/or too little is known to press ahead.
Critics and advocates generally agree that most outstanding questions on the impact, safety and efficacy of ocean iron fertilization can only be answered by much larger studies. Several such large scale pilot projects (covering approximately 10,000 km²) are currently being organized for 2007 and 2008
[26] in collaboration with various ocean institutes and university laboratories. Initial reports on their findings should be available by winter 2007.
See also
★
Carbon dioxide sink
References
1. Engineering a large sustainable world fishery, , I.S.F., Jones, Environmental Conservation,
2. John Martin (1935-1993)
3. Ocean Iron Fertilization - Why Dump Iron into the Ocean
4. Ironex (Iron Experiment) I
5. Ironex II, 1995
6. SOIREE (Southern Ocean Iron Release Experiment), 1999
7. EisenEx (Iron Experiment), 2000
8. SEEDS (Subarctic Pacific Iron Experiment for Ecosystem Dynamics Study), 2001
9. SOFeX (Southern Ocean Iron Experiments - North & South), 2002
10.
11. SERIES (Subarctic Ecosystem Response to Iron Enrichment Study), 2002
12. SEEDS-II, 2004
13. EIFEX (European Iron Fertilization Experiment), 2004
14. CROZEX (CROZet natural iron bloom and Export experiment), 2005
15. Volcanic iron, CO2, ocean productivity and climate, , A.J., Watson, Nature,
16. Ocean Plant Life Slows Down and Absorbs less Carbon NASA Earth Observatory
17. Iron uptake and growth limitation in oceanic and coastal phytoplankton, Sunda, W. G., and S. A. Huntsman, 1995. Mar. Chem. 50: 189–206
18. 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
19. Changing concentrations of CO, CH4, C5H8, CH3Br, CH3I, and dimethyl sulfide during the Southern Ocean Iron Enrichment Experiments, , Oliver W., Wingenter, Proceedings of the National Academy of Sciences,
20. Feb 2007 Carbon Update, CO2 Australia
21. Ocean Plant Life Slows Down and Absorbs less Carbon NASA Earth Observatory
22. Plankton Found to Absorb Less Carbon Dioxide BBC, 8/30/06
23. Greening-up the Ocean, Scienceline
24. Recruiting Plankton to Fight Global Warming, New York Times, Business Section, page 1, 5/1/07
25. Goal of ocean 'iron fertilization' said still unproved
26. Scientists to fight global warming with plankton ecoearth.info
Changing ocean processes
★
Global Change and Oceanic Primary Productivity: Effects of Ocean-Atmosphere-Biological Feedbacks - A. J. Miller et al., 2003
★
The Processes of the Ocean's Biological Pump and CO2 Sequestration - Jun Nishioka, 2002
Micronutrient iron and ocean productivity
★
Open Ocean Iron Fertilization for Scientific Study and Carbon Sequestration - K. Coale, 2001
★
Ocean Fertilisation - V. Smetecek, 2004
★
Sequestration of CO2 by Ocean Fertilization - 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
★ A Massive Phytoplankton Bloom Induced by an Ecosystem-Scale Iron Fertilization Experiment in the Equatorial Pacific Ocean, K. Coale et al., October 1996, Nature, Vol. 383 No. 6600
★ Iron Seeding Creates Fleeting Carbon Sink in Southern Ocean, Quirin Schmiermeier, 2004 Nature, Vol. 428 No. 6985
★ Diatoms and the Ocean Carbon Cycle, Victor Smetecek, March 1999, Protist, Vol. 150 No. 1
★ Differential Response of Equatorial Pacific Phytoplankton to Iron Fertilization, Kent Cavender-Bares et al., March 1999, Limnology and Oceanography, Vol. 44 No. 2
★ Coale, K.H. et al. (1996) A massive phytoplankton bloom induced by an ecosystem-scale iron fertilization experiment in the equatorial Pacific Ocean. Nature, 383, 495-501.
Ocean biomass carbon sequestration
★ Oceanic Sinks for Atmospheric CO2, J.A. Raven and P.G. Falkowski, June 1999, Plant, Cell and Environment, Vol.22 No. 6
★ Zooplankton Fecal Pellets, Marine Snow and Sinking Phytoplankton Blooms, Jefferson T. Turner, February 2002, Aquatic Microbial Ecology, Vol. 27 No. 1
★ Phytoplankton and Their Role in Primary, New and Export Production, Paul Falkowski et al., 2003, Ocean Biogeochemistry, Chapter 4, Ed. Michael J.R. Fasham, Springer 2003
★ Markels, M and R T Barber (2001) Sequestration of CO2 by Ocean Fertilization. Proc 1st Nat. Conf. on Carbon Sequestration, Washington, DC.
Ocean carbon cycle modeling
★ Carbon Dioxide Fluxes in the Global Ocean, Andrew Watson and James Orr, 2003, Ocean Biogeochemistry, Chapter 5, Ed. Michael J.R. Fasham, Springer 2003
★ Three-Dimensional Simulations of the Impact of Southern Ocean Nutrient Depletion on Atmospheric CO2 and Ocean Chemistry, J.L. Sarmiento and J.C. Orr, December 1991, Limnology and Oceanography, Vol. 36 No. 8
External links
Technique
★
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- treehugger.com
★
''Dumping Iron'' - Wired News
Context
★
Global Impact of Ocean Nourishment - I.S.F. Jones, Berkeley
Debate
★
The Iron Shore Of Science Journalism
★
An Open Letter to the Marine Science Community: Has Personal Bias Derailed Science?
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