Iron fertilization

Iron fertilization

Overview
Iron fertilization is the intentional introduction of iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

 to the upper ocean
Ocean
An ocean is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas.More than half of this area is over 3,000...

 to stimulate a phytoplankton
Phytoplankton
Phytoplankton are the autotrophic component of the plankton community. The name comes from the Greek words φυτόν , meaning "plant", and πλαγκτός , meaning "wanderer" or "drifter". Most phytoplankton are too small to be individually seen with the unaided eye...

 bloom. This is intended to enhance biological productivity, which can benefit the marine food chain
Food chain
A food web depicts feeding connections in an ecological community. Ecologists can broadly lump all life forms into one of two categories called trophic levels: 1) the autotrophs, and 2) the heterotrophs...

 and remove carbon dioxide
Biological pump
In oceanic biogeochemistry, the biological pump is the sum of a suite of biologically-mediated processes that transport carbon from the surface euphotic zone to the ocean's interior.-Overview:...

 from the atmosphere. Iron is a trace element necessary for photosynthesis
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...

 in all plants. It is highly insoluble in sea water and is often the limiting nutrient
Nutrient
A nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment. They are used to build and repair tissues, regulate body processes and are converted to and used as energy...

 for phytoplankton growth. Large phytoplankton blooms can be created by supplying iron to iron-deficient ocean waters.
Discussion
Ask a question about 'Iron fertilization'
Start a new discussion about 'Iron fertilization'
Answer questions from other users
Full Discussion Forum
 
Recent Discussions
Encyclopedia
Iron fertilization is the intentional introduction of iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

 to the upper ocean
Ocean
An ocean is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas.More than half of this area is over 3,000...

 to stimulate a phytoplankton
Phytoplankton
Phytoplankton are the autotrophic component of the plankton community. The name comes from the Greek words φυτόν , meaning "plant", and πλαγκτός , meaning "wanderer" or "drifter". Most phytoplankton are too small to be individually seen with the unaided eye...

 bloom. This is intended to enhance biological productivity, which can benefit the marine food chain
Food chain
A food web depicts feeding connections in an ecological community. Ecologists can broadly lump all life forms into one of two categories called trophic levels: 1) the autotrophs, and 2) the heterotrophs...

 and remove carbon dioxide
Biological pump
In oceanic biogeochemistry, the biological pump is the sum of a suite of biologically-mediated processes that transport carbon from the surface euphotic zone to the ocean's interior.-Overview:...

 from the atmosphere. Iron is a trace element necessary for photosynthesis
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...

 in all plants. It is highly insoluble in sea water and is often the limiting nutrient
Nutrient
A nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment. They are used to build and repair tissues, regulate body processes and are converted to and used as energy...

 for phytoplankton growth. Large phytoplankton 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
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

 in the deep ocean, and to increase marine biological productivity which is likely in decline as a result of climate change
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...

. Since 1993, thirteen international research teams have completed ocean trials demonstrating that phytoplankton blooms can be stimulated by iron addition. However, controversy remains over the effectiveness of atmospheric sequestration and ecological effects. The most recent open ocean trial of ocean iron fertilization, dubbed LOHAFEX, was conducted from January to March 2009 in the South Atlantic.

Fertilization also occurs naturally when upwelling
Upwelling
Upwelling is an oceanographic phenomenon that involves wind-driven motion of dense, cooler, and usually nutrient-rich water towards the ocean surface, replacing the warmer, usually nutrient-depleted surface water. The increased availability in upwelling regions results in high levels of primary...

s bring nutrient-rich water to the surface, as occurs when ocean currents meet an ocean bank
Bank (topography)
A bank, sometimes referred to as a fishing bank, is an area on the continental shelf which is shallow compared to its surrounding area, such as a shoal or the top of an underwater hill. Somewhat like continental slopes, ocean banks slopes can upwell as tidal and other flows intercept them,...

 or a sea mount. This form of fertilization produces the world's largest marine habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...

s. 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 glacier
Glacier
A glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its ablation over many years, often centuries. At least 0.1 km² in area and 50 m thick, but often much larger, a glacier slowly deforms and flows due to stresses induced by its weight...

s, rivers and icebergs.

History


Consideration of iron's importance to phytoplankton growth and photosynthesis dates back to the 1930s when English biologist
Biologist
A biologist is a scientist devoted to and producing results in biology through the study of life. Typically biologists study organisms and their relationship to their environment. Biologists involved in basic research attempt to discover underlying mechanisms that govern how organisms work...

  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
John Martin (oceanographer)
John Martin , was an oceanographer.Born in Old Lyme, Connecticut, he is best known for his research on the role of iron as a phytoplankton micronutrient, and its significance for so-called "High-Nutrient, Low Chlorophyll" regions of the oceans...

 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
HNLC
HNLC stands for "high-nitrate, low-chlorophyll" - a term used in marine ecology to describe areas of the ocean where the number of phytoplankton are low and fairly constant in spite of high macro-nutrient concentrations...

) zones.

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 1991 quip three years later at Woods Hole Oceanographic Institution
Woods Hole Oceanographic Institution
The Woods Hole Oceanographic Institution is a private, nonprofit research and higher education facility dedicated to the study of all aspects of marine science and engineering and to the education of marine researchers. Established in 1930, it is the largest independent oceanographic research...

, "Give me a half a tanker of iron and I will give you another ice age
Ice age
An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...

", drove a decade of research whose findings suggested that iron deficiency was not merely impacting ocean ecosystem
Ecosystem
An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....

s, it also offered a key to mitigating climate change
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...

 as well.

Perhaps the most dramatic support for Martin's hypothesis was seen in the aftermath of the 1991 eruption of Mount Pinatubo
Mount Pinatubo
Mount Pinatubo is an active stratovolcano located on the island of Luzon, near the tripoint of the Philippine provinces of Zambales, Tarlac, and Pampanga. It is located in the Tri-Cabusilan Mountain range separating the west coast of Luzon from the central plains, and is west of the dormant and...

 in the Philippines
Philippines
The Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...

. Environmental scientist Andrew Watson
Andrew Watson (scientist)
Andrew James Watson FRS is a British marine and atmospheric scientist and an expert in processes affecting atmospheric carbon dioxide and oxygen concentrations...

 analyzed global data from that eruption and calculated that it deposited approximately 40,000 tons of iron dust
Dust
Dust consists of particles in the atmosphere that arise from various sources such as soil dust lifted up by wind , volcanic eruptions, and pollution...

 into the oceans worldwide. This single fertilization event generated an easily observed global decline in atmospheric  and a parallel pulsed increase in oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

 levels.

Experiments


Martin hypothesized that increasing phytoplankton photosynthesis could slow or even reverse global warming
Global warming
Global warming refers to the rising average temperature of Earth's atmosphere and oceans and its projected continuation. In the last 100 years, Earth's average surface temperature increased by about with about two thirds of the increase occurring over just the last three decades...

 by sequestering enormous volume
Volume
Volume is the quantity of three-dimensional space enclosed by some closed boundary, for example, the space that a substance or shape occupies or contains....

s of 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
Galápagos Islands
The Galápagos Islands are an archipelago of volcanic islands distributed around the equator in the Pacific Ocean, west of continental Ecuador, of which they are a part.The Galápagos Islands and its surrounding waters form an Ecuadorian province, a national park, and a...

 in 1993 by his colleagues at Moss Landing Marine Laboratories
Moss Landing Marine Laboratories
The Moss Landing Marine Laboratories is a multi-campus marine research consortium headquartered at Moss Landing, California.-Organization:...

. Since then 9 international ocean studies have examined the fertilization effects of iron:
  • Ironex II, 1995
  • SOIREE (Southern Ocean Iron Release Experiment), 1999
  • EisenEx (Iron Experiment), 2000
  • SEEDS (Subarctic Pacific Iron Experiment for Ecosystem Dynamics Study), 2001
  • SOFeX (Southern Ocean Iron Experiments - North & South), 2002
  • SERIES (Subarctic Ecosystem Response to Iron Enrichment Study), 2002
  • SEEDS-II, 2004
  • EIFEX (European Iron Fertilization Experiment), 2004
  • CROZEX (CROZet natural iron bloom and Export experiment), 2005
  • LOHAFEX (India
    India
    India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

    n and German
    Germany
    Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

     Iron Fertilization Experiment), 2009


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
Silicic acid
Silicic acid is a general name for a family of chemical compounds of the element silicon, hydrogen, and oxygen, with the general formula [SiOx4-2x]n...

 which is likely to affect the efficacy of carbon sequestration. A 900 square kilometres (347.5 sq mi) portion of the southwest Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...

 was fertilized with iron sulfate
Iron sulfate
Iron sulfate may refer to:*Ferrous sulphate, Iron sulfate, FeSO4*Ferric sulphate, Iron sulfate, Fe23...

. A large phytoplankton bloom was triggered, however this bloom did not contain diatom
Diatom
Diatoms are a major group of algae, and are one of the most common types of phytoplankton. Most diatoms are unicellular, although they can exist as colonies in the shape of filaments or ribbons , fans , zigzags , or stellate colonies . Diatoms are producers within the food chain...

s because the fertilized location was already depleted in silicic acid
Silicic acid
Silicic acid is a general name for a family of chemical compounds of the element silicon, hydrogen, and oxygen, with the general formula [SiOx4-2x]n...

, an essential nutrient for diatom growth. 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. 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.

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, which is almost sufficient to reverse the warming effect of about 1/6 of current levels of anthropogenic
Anthropogenic
Human impact on the environment or anthropogenic impact on the environment includes impacts on biophysical environments, biodiversity and other resources. The term anthropogenic designates an effect or object resulting from human activity. The term was first used in the technical sense by Russian...

  emissions. It is notable, however, that the addition of silicic acid or choosing the proper location could, at least mathematically, eliminate and exceed all man made CO2. Further tests and experiments are required to test this theory and observe potential negative impact.

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
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...

. 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
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...

 that has historically been delivered to the pelagic sea
Pelagic zone
Any water in a sea or lake that is not close to the bottom or near to the shore can be said to be in the pelagic zone. The word pelagic comes from the Greek πέλαγος or pélagos, which means "open sea". The pelagic zone can be thought of in terms of an imaginary cylinder or water column that goes...

 by dust storm
Dust storm
A dust / sand storm is a meteorological phenomenon common in arid and semi-arid regions. Dust storms arise when a gust front or other strong wind blows loose sand and dirt from a dry surface. Particles are transported by saltation and suspension, causing soil to move from one place and deposition...

s from arid lands. This Aeolian dust contains 3–5% iron and its deposition has fallen nearly 25% in recent decades.

The Redfield ratio
Redfield ratio
Redfield ratio or Redfield stoichiometry is the molecular ratio of carbon, nitrogen and phosphorus in plankton. This empirically developed stoichiometric ratio is found to be C:N:P = 106:16:1. This term is named after the American oceanographer Alfred C. Redfield, who first described this ratio in...

 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
Phosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...

 and 16 of nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

 are required to "fix
Carbon fixation
In biology, carbon fixation is the reduction of carbon dioxide to organic compounds by living organisms. The obvious example is photosynthesis. Carbon fixation requires both a source of energy such as sunlight, and an electron donor such as water. All life depends on fixed carbon. Organisms that...

" 106 carbon atoms (or 106 molecules of ). 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, 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".

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.

Carbon sequestration



Previous instances of biological carbon sequestration have triggered major climatic changes, such as the Azolla event
Azolla event
The Azolla event occurred in the middle Eocene period, around , when blooms of the freshwater fern Azolla are thought to have happened in the Arctic Ocean...

. Plankton that generate calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...

 or silicon
Silicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...

 carbonate
Carbonate
In chemistry, a carbonate is a salt of carbonic acid, characterized by the presence of the carbonate ion, . The name may also mean an ester of carbonic acid, an organic compound containing the carbonate group C2....

 skeletons, such as diatom
Diatom
Diatoms are a major group of algae, and are one of the most common types of phytoplankton. Most diatoms are unicellular, although they can exist as colonies in the shape of filaments or ribbons , fans , zigzags , or stellate colonies . Diatoms are producers within the food chain...

s, coccolithophore
Coccolithophore
Coccolithophores are single-celled algae, protists, and phytoplankton belonging to the division of haptophytes. They are distinguished by special calcium carbonate plates of uncertain function called coccoliths , which are important microfossils...

s and foraminifera
Foraminifera
The Foraminifera , or forams for short, are a large group of amoeboid protists which are among the commonest plankton species. They have reticulating pseudopods, fine strands of cytoplasm that branch and merge to form a dynamic net...

, 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
In the deep ocean, marine snow is a continuous shower of mostly organic detritus falling from the upper layers of the water column. It is a significant means of exporting energy from the light-rich photic zone to the aphotic zone below. The term was first coined by the explorer William Beebe as he...

. 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 plankton blooms, half (or more) is generally consumed by grazing organisms (zooplankton
Zooplankton
Zooplankton are heterotrophic plankton. Plankton are organisms drifting in oceans, seas, and bodies of fresh water. The word "zooplankton" is derived from the Greek zoon , meaning "animal", and , meaning "wanderer" or "drifter"...

, krill
Krill
Krill is the common name given to the order Euphausiacea of shrimp-like marine crustaceans. Also known as euphausiids, these small invertebrates are found in all oceans of the world...

, small fish, etc.) but 20 to 30% sinks below 200 metres (656.2 ft) into the colder water strata below the thermocline
Thermocline
A thermocline is a thin but distinct layer in a large body of fluid , in which temperature changes more rapidly with depth than it does in the layers above or below...

. 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.)

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 measurements, including a combination of ship-borne and remote sampling, submarine filtration traps, tracking buoy spectroscopy
Spectroscopy
Spectroscopy is the study of the interaction between matter and radiated energy. Historically, spectroscopy originated through the study of visible light dispersed according to its wavelength, e.g., by a prism. Later the concept was expanded greatly to comprise any interaction with radiative...

 and satellite telemetry. Unpredictable ocean currents have been known to remove experimental iron patches from the pelagic zone, invalidating the experiment.

The potential of iron fertilization as a geoengineering
Geoengineering
The concept of Geoengineering refers to the deliberate large-scale engineering and manipulation of the planetary environment to combat or counteract anthropogenic changes in atmospheric chemistry The Intergovernmental Panel on Climate Change concluded in 2007 that geoengineering options, such...

 technique to tackle global warming is illustrated by the following figures. If phytoplankton
Phytoplankton
Phytoplankton are the autotrophic component of the plankton community. The name comes from the Greek words φυτόν , meaning "plant", and πλαγκτός , meaning "wanderer" or "drifter". Most phytoplankton are too small to be individually seen with the unaided eye...

 converted all the nitrate
Nitrate
The nitrate ion is a polyatomic ion with the molecular formula NO and a molecular mass of 62.0049 g/mol. It is the conjugate base of nitric acid, consisting of one central nitrogen atom surrounded by three identically-bonded oxygen atoms in a trigonal planar arrangement. The nitrate ion carries a...

 and phosphate
Phosphate
A phosphate, an inorganic chemical, is a salt of phosphoric acid. In organic chemistry, a phosphate, or organophosphate, is an ester of phosphoric acid. Organic phosphates are important in biochemistry and biogeochemistry or ecology. Inorganic phosphates are mined to obtain phosphorus for use in...

 present in the surface mixed layer across the entire Antarctic circumpolar current
Antarctic Circumpolar Current
The Antarctic Circumpolar Current is an ocean current that flows from west to east around Antarctica. An alternative name for the ACC is the West Wind Drift. The ACC is the dominant circulation feature of the Southern Ocean and, at approximately 125 Sverdrups, the largest ocean current...

 into organic carbon, the resulting carbon dioxide deficit could be compensated by uptake from the atmosphere
Atmosphere
An atmosphere is a layer of gases that may surround a material body of sufficient mass, and that is held in place by the gravity of the body. An atmosphere may be retained for a longer duration, if the gravity is high and the atmosphere's temperature is low...

 amounting to about 0.8 to 1.4 gigatonnes of carbon per year. This quantity is comparable in magnitude to annual anthropogenic
Anthropogenic
Human impact on the environment or anthropogenic impact on the environment includes impacts on biophysical environments, biodiversity and other resources. The term anthropogenic designates an effect or object resulting from human activity. The term was first used in the technical sense by Russian...

 fossil fuels combustion of approximately 6 gigatonnes. It should be noted that the Antarctic circumpolar current
Antarctic Circumpolar Current
The Antarctic Circumpolar Current is an ocean current that flows from west to east around Antarctica. An alternative name for the ACC is the West Wind Drift. The ACC is the dominant circulation feature of the Southern Ocean and, at approximately 125 Sverdrups, the largest ocean current...

 region is only one of several in which iron fertilization could be conducted—the Galapagos islands area being another potentially suitable location.

Dimethyl sulfide and clouds


Some species of plankton produce dimethyl sulfide
Dimethyl sulfide
Dimethyl sulfide or methylthiomethane is an organosulfur compound with the formula 2S. Dimethyl sulfide is a water-insoluble flammable liquid that boils at and has a characteristic disagreeable odor. It is a component of the smell produced from cooking of certain vegetables, notably maize,...

 (DMS), a portion of which enters the atmosphere where it is oxidized by hydroxyl radical
Hydroxyl radical
The hydroxyl radical, •OH, is the neutral form of the hydroxide ion . Hydroxyl radicals are highly reactive and consequently short-lived; however, they form an important part of radical chemistry. Most notably hydroxyl radicals are produced from the decomposition of hydroperoxides or, in...

s (OH), atomic chlorine
Chlorine
Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...

 (Cl) and bromine
Bromine
Bromine ") is a chemical element with the symbol Br, an atomic number of 35, and an atomic mass of 79.904. It is in the halogen element group. The element was isolated independently by two chemists, Carl Jacob Löwig and Antoine Jerome Balard, in 1825–1826...

 monoxide (BrO) to form sulfate particles and ultimately clouds. This may increase the albedo
Albedo
Albedo , or reflection coefficient, is the diffuse reflectivity or reflecting power of a surface. It is defined as the ratio of reflected radiation from the surface to incident radiation upon it...

 of the planet and so cause cooling. This is the basic tenet of the Gaia hypothesis
Gaia hypothesis
The Gaia hypothesis, also known as Gaia theory or Gaia principle, proposes that all organisms and their inorganic surroundings on Earth are closely integrated to form a single and self-regulating complex system, maintaining the conditions for life on the planet.The scientific investigation of the...

 and was presented in James Lovelock
James Lovelock
James Lovelock, CH, CBE, FRS is an independent scientist, environmentalist and futurologist who lives in Devon, England. He is best known for proposing the Gaia hypothesis, which postulates that the biosphere is a self-regulating entity with the capacity to keep our planet healthy by controlling...

's first paper published on this topic.

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 uptake and that due to the ocean's albedo increase, however the amount of cooling by this particular effect is very uncertain.

Financial opportunities


Since the advent of the Kyoto Protocol
Kyoto Protocol
The Kyoto Protocol is a protocol to the United Nations Framework Convention on Climate Change , aimed at fighting global warming...

, several countries and the European Union
European Union
The European Union is an economic and political union of 27 independent member states which are located primarily in Europe. The EU traces its origins from the European Coal and Steel Community and the European Economic Community , formed by six countries in 1958...

 have established carbon offset markets which trade certified emission reduction credits
Emissions trading
Emissions trading is a market-based approach used to control pollution by providing economic incentives for achieving reductions in the emissions of pollutants....

 (CERs) and other types of carbon credit instruments internationally. In 2007 CERs sell for approximately €15–20/ton and European analysts project these prices will nearly double by 2012. Iron fertilization is relatively inexpensive compared to scrubbing
Scrubber
Scrubber systems are a diverse group of air pollution control devices that can be used to remove some particulates and/or gases from industrial exhaust streams. Traditionally, the term "scrubber" has referred to pollution control devices that use liquid to wash unwanted pollutants from a gas stream...

, direct injection and other industrial approaches, and can theoretically sequester for less than €5/ton , creating a substantial return. In August, 2010, Russia established a minimum price of €10/ton for offsets to reduce uncertainty for offset providers.
Scientists have reported a minimum 6–12% decline in global plankton production since 1980, 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.

Multilateral reaction


The parties to the London Dumping Convention (Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter 1972) 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".

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).

Sequestration definitions


Carbon is not considered "sequestered" unless it settles to the ocean floor where it remains for eons. 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.

Advocates argue that modern climate scientists and Kyoto Protocol
Kyoto Protocol
The Kyoto Protocol is a protocol to the United Nations Framework Convention on Climate Change , aimed at fighting global warming...

 policy makers define sequestration in much shorter time frames. For example, they recognize trees and grasslands as important carbon sinks. Forest biomass
Biomass
Biomass, as a renewable energy source, is biological material from living, or recently living organisms. As an energy source, biomass can either be used directly, or converted into other energy products such as biofuel....

 only sequesters carbon for decades, but carbon that sinks below the marine thermocline
Thermocline
A thermocline is a thin but distinct layer in a large body of fluid , in which temperature changes more rapidly with depth than it does in the layers above or below...

 (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.

Debate


While many advocates of ocean iron fertilization see it as modern society's last best hope to slow global warming, some academics, deep greens
Deep ecology
Deep ecology is a contemporary ecological philosophy that recognizes an inherent worth of all living beings, regardless of their instrumental utility to human needs. The philosophy emphasizes the interdependence of organisms within ecosystems and that of ecosystems with each other within the...

 and proponents of competing technologies cite a variety of concerns.

Precautionary principle


The precautionary principle (PP) states that if an action or policy has a suspected risk of causing harm, in the absence of scientific consensus
Scientific consensus
Scientific consensus is the collective judgment, position, and opinion of the community of scientists in a particular field of study. Consensus implies general agreement, though not necessarily unanimity. Scientific consensus is not by itself a scientific argument, and it is not part of the...

, 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. Such large and rapid conversions have no precedent.

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

20th century phytoplankton decline


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, but two others found increases in phytoplankton.


Comparison to prior phytoplankton cycles


Fertilization advocates respond that similar algal bloom
Algal bloom
An algal bloom is a rapid increase or accumulation in the population of algae in an aquatic system. Algal blooms may occur in freshwater as well as marine environments. Typically, only one or a small number of phytoplankton species are involved, and some blooms may be recognized by discoloration...

s have occurred naturally for millions of years with no observed ill effects. The Azolla event
Azolla event
The Azolla event occurred in the middle Eocene period, around , when blooms of the freshwater fern Azolla are thought to have happened in the Arctic Ocean...

 occurred around 49 million years ago and accomplished what fertilization is intended to achieve (but on a larger scale).

Sequestration efficiency


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. 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.

The counter-argument to this is that the low sequestration estimates that emerged from some ocean trials are largely due to these factors:
  1. Data: none of the ocean trials had enough boat time to monitor their blooms for more than 27 days, 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 1000 kilograms (2,204.6 lb) of iron and thus created small blooms that were quickly devoured by opportunistic zooplankton
    Zooplankton
    Zooplankton are heterotrophic plankton. Plankton are organisms drifting in oceans, seas, and bodies of fresh water. The word "zooplankton" is derived from the Greek zoon , meaning "animal", and , meaning "wanderer" or "drifter"...

    , krill
    Krill
    Krill is the common name given to the order Euphausiacea of shrimp-like marine crustaceans. Also known as euphausiids, these small invertebrates are found in all oceans of the world...

    , and fish that swarmed into the seeded region.


Some ocean trials reported positive results. IronEx II reported conversion of 1000 kilograms (2,204.6 lb) to carbonaceous biomass
Biomass
Biomass, as a renewable energy source, is biological material from living, or recently living organisms. As an energy source, biomass can either be used directly, or converted into other energy products such as biofuel....

 equivalent to one hundred full-grown redwood
Sequoiadendron
Sequoiadendron giganteum is the sole living species in the genus Sequoiadendron, and one of three species of coniferous trees known as redwoods, classified in the family Cupressaceae in the subfamily Sequoioideae, together with Sequoia sempervirens and...

s within two weeks. Eifex recorded 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 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).

Algal blooms




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 tide
Red tide
Red tide is a common name for a phenomenon also known as an algal bloom , an event in which estuarine, marine, or fresh water algae accumulate rapidly in the water column and results in discoloration of the surface water. It is usually found in coastal areas...

s and other toxic phenomena. These factors affect only near-shore waters, although they show that increased phytoplankton populations are not universally benign.

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.

A 2010 study of iron fertilization in an oceanic high-nitrate, low-chlorophyll environment, however, found that fertilized Pseudo-nitzschia
Pseudo-nitzschia
The genus Pseudo-nitzschia includes several species of diatoms known to produce the neurotoxin known as domoic acid, a toxin which is responsible for the human illness called amnesic shellfish poisoning...

diatom spp., which are generally nontoxic in the open ocean, began producing toxic levels of domoic acid
Domoic acid
Domoic acid , the neurotoxin that causes amnesic shellfish poisoning , also known as zombie acid, is a kainic acid analog, heterocyclic amino acid associated with certain harmful algal blooms.-Occurrence:...

. Even short-lived blooms containing such toxins could have detrimental effects on marine food webs.

Deep water oxygen levels


When organic bloom detritus sinks into the abyss, a significant fraction will be devoured by bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

, other microorganisms and deep sea animals which also consume oxygen. A large enough bloom could render certain regions of the sea deep beneath it anoxic and threaten other benthic species.

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.

Ecosystem effects


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
Jellyfish
Jellyfish are free-swimming members of the phylum Cnidaria. Medusa is another word for jellyfish, and refers to any free-swimming jellyfish stages in the phylum Cnidaria...

, disturbance of the food chain impacting whale
Whale
Whale is the common name for various marine mammals of the order Cetacea. The term whale sometimes refers to all cetaceans, but more often it excludes dolphins and porpoises, which belong to suborder Odontoceti . This suborder also includes the sperm whale, killer whale, pilot whale, and beluga...

 populations or fisheries are potential risks.

A 2010 study shows that iron enrichment stimulates toxic diatom
Diatom
Diatoms are a major group of algae, and are one of the most common types of phytoplankton. Most diatoms are unicellular, although they can exist as colonies in the shape of filaments or ribbons , fans , zigzags , or stellate colonies . Diatoms are producers within the food chain...

 production in high-nitrate, low-chlorophyll areas http://www.pnas.org/content/107/13/5887, which, the authors argue, raises "serious concerns over the net benefit and sustainability of large-scale iron fertilizations".

However, -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.

Conclusion and further research


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.

A statement published in Science in 2008 maintained that it would be

One pilot project planned by Planktos, a U.S. company, was cancelled in 2008 for lack of funding. The company blamed environmental organizations for the failure.

See also

  • Carbon dioxide sink
    Carbon dioxide sink
    A carbon sink is a natural or artificial reservoir that accumulates and stores some carbon-containing chemical compound for an indefinite period. The process by which carbon sinks remove carbon dioxide from the atmosphere is known as carbon sequestration...

  • Iron chelate
    Iron chelate
    Iron chelate, also known as chelated iron, is a soluble complex of iron, sodium and a chelating agent such as ethylenediaminetetraacetate , EDDHA, or others, used to make the iron soluble in water and, for the purposes of agriculture, accessible to plants.It is encountered as a dark brownish...

  • Iron Hypothesis
    Iron Hypothesis
    The Iron Hypothesis was formulated by oceanographer John Martin, based on theories by Joseph Hart and first tested in 1993. In 1988, Nature published the results of Martin's experiments as well as his speculations on climate change...

  • Ocean pipes
  • Liebig's law of the minimum
    Liebig's law of the minimum
    Liebig's Law of the Minimum, often simply called Liebig's Law or the Law of the Minimum, is a principle developed in agricultural science by Carl Sprengel and later popularized by Justus von Liebig...


Changing ocean processes


Micronutrient iron and ocean productivity


Technique


Context




Debate