Iron fertilization

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Iron fertilization is a method to encourage 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 CO₂ to slow down global warming. Since 1993, ten international research teams have completed relatively small-scale ocean trials demonstrating the effect, and substantially larger pilot projects are planned for 2006.

Contents 1 History 2 Motivations 2.1 Ecological Issues 2.2 Climatic Effects 2.3 Financial Opportunities 3 Science 3.1 DMS (Dimethyl sulfide) 4 Debate 4.1 Precautionary Principle 4.2 Inadequacies 4.3 Sequestration Definitions 4.4 Ecological Issues 4.4.1 Harmful Algal Blooms (HAB) 4.4.2 Deep water oxygen depletion 4.4.3 Ecosystem Alterations 4.5 Conclusion and Further Research 5 References 5.1 Background on Climate Change and the Oceans 5.2 Changing Ocean Processes 5.3 Declining Ocean Productivity 5.4 Micronutrient Iron and Ocean Productivity 5.5 Ocean Biomass Carbon Sequestration 5.6 Ocean Carbon Cycle Modeling 6 External links 6.1 Technique 6.2 Context

[edit] 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.

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," vernacularized a decade of research findings that suggested iron deficiency was not merely impacting ocean ecosystems, it also offered a key to mitigating climate change as well. Martin hypothesized that restoring high levels of plankton photosynthesis could slow or even reverse global warming by sequestering enormous volumes of CO₂ in the sea. He died shortly thereafter during preparations for Ironex I, 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 (Iron Experiment) II, '95; SOIREE (Southern Ocean Iron Release Experiment), '99; EisenEx (Eisen Experiment), '00; SEEDS (Subarctic Pacific Iron Experiment for Ecosystem Dynamics Study), '01; SOFeX (Southern Ocean Iron Experiments - North & South), '02; SERIES (Subarctic Ecosystem Response to Iron Enrichment Study), '02; SEEDS-II, '04; EIFEX (European Iron Fertilization Experiment); '04; and CROZEX (CROZet natural iron bloom and Export experiment), '05.

Perhaps the most dramatic vindication of 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 CO₂ and a parallel pulsed increase in oxygen levels. (See Watson, A.J. "Volcanic iron, CO₂, ocean productivity and climate." Nature, 385, 587-588, 1997)

[edit] Motivations

There are several key issues fueling interest in this technology, including ecological, climatic and financial concerns.

[edit] Ecological Issues

NASA and NOAA recently reported that since the early 1980s marine phytoplankton populations have declined by over 20% in the Pacific Ocean and 6~9% globally. Since these plankton constitute the base of the entire marine food pyramid, their declining numbers mean less nourishment for all other marine species. This relationship was dramatized by the great plankton dieoff along America's Pacific Coast in the summer of 2005 that littered California beaches with thousands of fish and seabirds that had starved to death.

Most concerning, the southern ocean krill populations that feed directly on phytoplankton have plummeted nearly 80% over the same period. These small crustaceans are the primary food for penguins, other seabirds, many commercially important fisheries, and the most endangered whale species. Ocean scientists from Germany's Alfred Wegener Institute have in fact suggested that a large scale plankton restoration program in the cetacean nursery zones of the southern ocean could help return the krill-dependent great baleen whales (blue, humpback, gray, right, etc.) to healthy levels again in 10~20 years.

Besides recharging the marine food chain, iron-catalyzed plankton restoration could help reduce ocean surface acidification that has increased tenfold in the last two decades threatening the integrity of diatoms, foraminifera, coral and other creatures with acid-vulnerable carbonate skeletons. (Rising levels of atmospheric carbon dioxide increase concentrations of carbonic acid in surface waters, but phytoplankton blooms absorb large volumes of CO₂ during photosynthesis and help buffer the acidity.)

[edit] Climatic Effects

As John Martin envisioned from his water research and the paleoclimatological record, increasing plankton photosynthesis and primary productivity could have profound impacts on atmospheric CO₂ and global temperature.

Historically marine phytoplankton have annually absorbed and fixed nearly half of all planetary CO₂ emissions or approximately 50 billion tons. NASA and NOAA's most conservative estimate of global plankton decline in the last 25 years is at least 6%. Simply returning these populations to known 1980 levels of health and activity could therefore annually sequester 2~3 billion more tons of CO₂ than are being removed today or a third to one half of all current industrial and automotive emissions.

[edit] 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 2006 CERs sell for approximately €25/ton CO₂e, which suggests that a full-scale plankton restoration program could generate up to €75 billion 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. Given this potential return on investment, some carbon traders and offset customers are watching the progress of this technology with interest.

[edit] Science

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 due to modern changes in land use and agricultural practices as well as increased greening of dry regions thanks to increasing levels of atmospheric CO₂. (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 molecular concentrations of critical nutrients in plankton biomass and is conventionally written "106 C: 16 N: 1 P." This expresses the fact that one molecule of phosphorous and 16 of nitrogen are required to fix 106 carbon molecules. Recent research has expanded this constant to "106 C: 16 N: 1 P: .001 Fe" signifying that in iron deficient conditions each molecular unit of iron can fix over 100,000 units of carbon or 367,000 units of CO₂.

In "desolate" HNLC zones, therefore, small amounts of iron (measured in parts per trillion) delivered by either by the wind or a planned restoration program can trigger large responsive phytoplankton blooms. Recent marine trials confirm that one kilogram of fine iron particles can reliably generate well over 100,000 kilograms of plankton biomass. The size of the iron particles is critical, however, and particles of several micrometres 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.

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.

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.

[edit] DMS (Dimethyl sulfide)

Some species of plankton produce DMS, a portion of which enters the atmosphere where it is oxidized by hydroxy (HO), atomic chlorine (Cl)and bromine monoxide (BrO) to form sulfate particles and ultimately clouds. 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 would lead to substainal cooling well beyond increased CO₂ uptake (http://www.pnas.org/cgi/content/abstract/101/23/8537).

[edit] 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.

[edit] 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.

Advocates: Similar blooms have occurred naturally for millions of years with no observed ill effects. The precautionary principle provides a legitimate brake on this technique once plankton populations are restored to their known levels in 1980. Up to that point, however, plankton revival is simply eco-healing and little different from remedially treating superfund sites, oil spills or contaminated mothers milk.

Not even trying to remedy these industrial impacts is far more irresponsible considering the known pace of increasing harm.

[edit] Inadequacies

Critics: 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.[[1]]

Advocates: 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.

Nevertheless, 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 of CO₂ 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 the €20 billion. Considering EU penalties for Kyoto non-compliance will reach €100/ton CO₂e 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. ^{[citation needed]}

[edit] 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.

[edit] Ecological Issues

[edit] 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.^{[citation needed]}

[edit] Deep water oxygen depletion

Critics^{[citation needed]}: 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^{[citation needed]}: 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.

[edit] Ecosystem Alterations

Critics^{[citation needed]}: Depending upon the composition and timing of delivery, these iron infusions could preferentially favor certain species and alter surface ecosystems to unknown effect.

Advocates^{[citation needed]}: CO₂-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.

[edit] 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^{[citation needed]}. 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.^{[citation needed]}

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 2006 and 2007 in collaboration with various ocean institutes and university laboratories. Initial reports on their findings should be available by autumn 2006.

[edit] References

[edit] Background on Climate Change and the Oceans

• Biodiversity and Climate Change- UN Environment Programme
• Climate Change and Marine Plankton- Trends in Ecology and Evolution, Vol.20 No.6

[edit] 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
• Global Garden Grows Greener - NASA
• Recent trends in global ocean chlorophyll, Watson Gregg et al., February 2005, Geophysical Research Letters, Vol. 32

[edit] Declining Ocean Productivity

• Ocean Plant Life Slows Down and Absorbs Less Carbon - NASA
• Massive Decline in Plankton Stocks - Study - J. Lovell, 2005
• Decline of the Marine Ecosystem Caused by a Reduction in the Atlantic Overturning Circulation, Andreas Schmittner, March 2005, Nature, Vol. 434 No. 7033
• Slowing of the Atlantic Meridional Overturning Circulation at 25ºN, Harry Brydon et al., December 2005, Nature, Vol. 438 No. 7068

[edit] 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

[edit] Ocean Biomass Carbon Sequestration

• Antarctic Krill Provide Carbon Sink in Southern Ocean - British Antarctic Survey
• 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

[edit] 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

[edit] External links

[edit] 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

[edit] Context

• Ocean Plant Life Slows Down and Absorbs Less Carbon - NASA
• Global Garden Grows Greener - NASA
• Whales and Food Webs- Cool Antarctica
• Global Impact of Ocean Nourishment - I.S.F. Jones, Berkeley
• Thousands of Seabirds Dying along BC Coast - Vancouver Sun 2/24/06
• American global warming gas emissions accelerate to a record high - UK Guardian 12/22/05