Iron fertilization | Wikipedia audio article


Iron fertilization is the intentional introduction
of iron to iron-poor areas of the ocean surface to stimulate phytoplankton production. This is intended to enhance biological productivity
and/or accelerate carbon dioxide (CO2) sequestration from the atmosphere. Iron is a trace element necessary for photosynthesis
in plants. It is highly insoluble in sea water and in
a variety of locations is the limiting nutrient for phytoplankton growth. Large algal blooms can be created by supplying
iron to iron-deficient ocean waters. These blooms can nourish other organisms. Multiple ocean labs, scientists and businesses
have explored fertilization. Beginning in 1993, thirteen research teams
completed ocean trials demonstrating that phytoplankton blooms can be stimulated by
iron augmentation. Controversy remains over the effectiveness
of atmospheric CO2 sequestration and ecological effects. The most recent open ocean trials of ocean
iron fertilization were in 2009 (January to March) in the South Atlantic by project Lohafex,
and in July 2012 in the North Pacific off the coast of British Columbia, Canada, by
the Haida Salmon Restoration Corporation (HSRC).Fertilization occurs naturally when upwellings bring nutrient-rich
water to the surface, as occurs when ocean currents meet an ocean bank or a sea mount. This form of fertilization produces the world’s
largest marine habitats. Fertilization can also occur when weather
carries wind blown dust long distances over the ocean, or iron-rich minerals are carried
into the ocean by glaciers, rivers and icebergs.==History==
Consideration of iron’s importance to phytoplankton growth and photosynthesis dates 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
be iron-deficient. Little scientific discussion was recorded
until the 1980s, when oceanographer John Martin renewed controversy on the topic with his
marine water nutrient analyses. His studies supported Hart’s hypothesis. These “desolate” regions came to be called
“High Nutrient, Low Chlorophyll” (HNLC) zones.John Gribbin was the first scientist to publicly
suggest that climate change could be reduced by adding large amounts of soluble iron to
the oceans. Martin’s 1988 quip four months later at Woods
Hole Oceanographic Institution, “Give me a half a tanker of iron and I will give you
another ice age”, drove a decade of research. The findings suggested that iron deficiency
was limiting ocean productivity and offered an approach to mitigating climate change as
well. Perhaps the most dramatic support for Martin’s
hypothesis came with 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 oceans worldwide. This single fertilization event preceded an
easily observed global decline in atmospheric CO2 and a parallel pulsed increase in oxygen
levels.The parties to the London Dumping Convention adopted a non-binding resolution in 2008 on
fertilization (labeled LC-LP.1(2008)). The resolution states that ocean fertilization
activities, other than legitimate scientific research, “should be considered as contrary
to the aims of the Convention and Protocol and do not currently qualify for any exemption
from the definition of dumping”. 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).==Methods==
There are two ways of performing artificial iron fertilization: ship based direct into
the ocean and atmospheric deployment.===Ship based deployment===
Trials of ocean fertilization using iron sulphate added directly to the surface water from ships
are described in detail in the experiment section below.===Atmospheric sourcing===
Iron-rich dust rising into the atmosphere is a primary source of ocean iron fertilization. For example, wind blown dust from the Sahara
desert fertilizes the Atlantic Ocean and the Amazon rainforest. The naturally occurring iron oxide in atmospheric
dust reacts with hydrogen chloride from sea spray to produce iron chloride, which degrades
methane and other greenhouse gases, brightens clouds and eventually falls with the rain
in low concentration across a wide area of the globe. Unlike ship based deployment, no trials have
been performed of increasing the natural level of atmospheric iron. Expanding this atmospheric source of iron
could complement ship-based deployment.====Iron Salt Aerosol====
One proposed method to boost the atmospheric iron level is Iron Salt Aerosol. By adding Iron(III) chloride into the troposphere,
iron salt aerosol could increase natural cooling effects including methane removal, cloud brightening
and ocean fertilization, helping to prevent or reverse global warming.==Experiments==
Martin hypothesized that increasing phytoplankton photosynthesis could slow or even reverse
global warming by sequestering 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. Thereafter 12 international ocean studies
examined the phenomenon: 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), A successful experiment conducted in 2004
in a mesoscale ocean eddy in the South Atlantic resulted in a bloom of diatoms, a large portion
of which died and sank to the ocean floor when fertilization ended. In contrast to the LOHAFEX experiment, also
conducted in a mesoscale eddy, the ocean in the selected area contained enough dissolved
silicon for the diatoms to flourish. CROZEX (CROZet natural iron bloom and Export
experiment), 2005 A 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. LOHAFEX (Indian and German 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 which was likely to affect sequestration efficacy. A 900 square kilometers (350 sq mi) portion
of the southwest Atlantic was fertilized with iron sulfate. A large phytoplankton bloom was triggered. This bloom did not contain diatoms because
the site was depleted in silicic acid, 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 led to suggestions
that fertilization is not an effective carbon mitigation strategy in general. However, prior ocean fertilization experiments
in high silica locations revealed much higher carbon sequestration rates because of diatom
growth. LOHAFEX confirmed sequestration potential
depends strongly upon appropriate siting. Haida Salmon Restoration Corporation (HSRC),
2012 – funded by the Old Massett Haida band and managed by Russ George – dumped 100 tonnes
of iron sulphate into the Pacific into an eddy 200 nautical miles (370 km) west of the
islands of Haida Gwaii. This resulted in increased algae growth over
10,000 square miles (26,000 km2). Critics alleged George’s actions violated
the United Nations Convention on Biological Diversity (CBD) and the London convention
on the dumping of wastes at sea which prohibited such geoengineering experiments. On 15 July 2014, the resulting scientific
data was made available to the public.==Science==
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,
offsetting 1/6 of current levels of anthropogenic CO2 emissions. These benefits have been called into question
by research suggesting that fertilization with iron may deplete other essential nutrients
in the seawater causing reduced phytoplankton growth elsewhere — in other words, that
iron concentrations limit growth more locally than they do on a global scale.===Role of iron===
About 70% of the world’s surface is covered in oceans. The part of these where light can penetrate
is inhabited by algae (and other marine life). In some oceans, algae growth and reproduction
is limited by the amount of iron. Iron is a vital micronutrient for phytoplankton
growth and photosynthesis that has historically been delivered to the pelagic sea by dust
storms from arid lands. This Aeolian dust contains 3–5% iron and
its deposition has fallen nearly 25% in recent decades.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 CO2). Research 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 HNLC zones can trigger large phytoplankton blooms on the order of 100,000
kilograms of plankton per kilogram of iron. The size of the iron particles is critical. Particles of 0.5–1 micrometer or less seem
to be ideal both in terms of sink rate and bioavailability. Particles this small are easier for cyanobacteria
and other phytoplankton to incorporate and the churning of surface waters keeps them
in the euphotic or sunlit biologically active depths without sinking for long periods. Atmospheric deposition is an important iron
source. Satellite images and data (such as PODLER,
MODIS, MSIR) combined with back-trajectory analyses identified natural sources of iron–containing
dust. Iron-bearing dusts erode from soil and are
transported by wind. Although most dust sources are situated in
the Northern Hemisphere, the largest dust sources are located in northern and southern
Africa, North America, central Asia and Australia.Heterogeneous chemical reactions in the atmosphere modify
the speciation of iron in dust and may affect the bioavailability of deposited iron. The soluble form of iron is much higher in
aerosols than in soil (~0.5%). Several photo-chemical interactions with dissolved
organic acids increase iron solubility in aerosols. Among these, photochemical reduction of oxalate-bound
Fe(III) from iron-containing minerals is important. The organic ligand forms a surface complex
with the Fe (III) metal center of an iron-containing mineral (such as hematite or goethite). On exposure to solar radiation the complex
is converted to an excited energy state in which the ligand, acting as bridge and an
electron donor, supplies an electron to Fe(III) producing soluble Fe(II). Consistent with this, studies documented a
distinct diel variation in the concentrations of Fe (II) and Fe(III) in which daytime Fe(II)
concentrations exceed those of Fe(III).===Volcanic ash as an iron source===
Volcanic ash has a significant role in supplying the world’s oceans with iron. Volcanic ash is composed of glass shards,
pyrogenic minerals, lithic particles and other forms of ash that release nutrients at different
rates depending on structure and the type of reaction caused by contact with water.Increases
of biogenic opal in the sediment record are associated with increased iron accumulation
over the last million years. In August 2008, an eruption in the Aleutian
Islands deposited ash in the nutrient-limited Northeast Pacific. This ash and iron deposition resulted in one
of the largest phytoplankton blooms observed in the subarctic.===Carbon sequestration===Previous instances of biological carbon sequestration
triggered major climatic changes, lowering the temperature of the planet, such as the
Azolla event. Plankton that generate calcium or silicon
carbonate skeletons, such as diatoms, coccolithophores and foraminifera, account for most direct
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 steadily falls 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, krill, small fish, etc.) but 20 to 30% sinks
below 200 meters (660 ft) into the colder water strata below the thermocline. Much of this fixed carbon continues 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 involves a variety of measurements, combining ship-borne and
remote sampling, submarine filtration traps, tracking buoy spectroscopy and satellite telemetry. Unpredictable ocean currents can remove experimental
iron patches from the pelagic zone, invalidating the experiment. The potential of fertilization to tackle global
warming is illustrated by the following figures. If phytoplankton converted all the nitrate
and phosphate present in the surface mixed layer across the entire Antarctic circumpolar
current into organic carbon, the resulting carbon dioxide deficit could be compensated
by uptake from the atmosphere amounting to about 0.8 to 1.4 gigatonnes of carbon per
year. This quantity is comparable in magnitude to
annual anthropogenic fossil fuels combustion of approximately 6 gigatonnes. The Antarctic circumpolar current region is
one of several in which iron fertilization could be conducted—the Galapagos islands
area another potentially suitable location.===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 potentially increase cloud cover. This may increase the albedo of the planet
and so cause cooling—this proposed mechanism is central to the CLAW hypothesis. This is one of the examples used by James
Lovelock to illustrate his Gaia hypothesis.During 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 CO2
uptake and that due to the ocean’s albedo increase, however the amount of cooling by
this particular effect is very uncertain.==Financial opportunities==
Beginning with the Kyoto Protocol, several countries and the European Union established
carbon offset markets which trade certified emission reduction credits (CERs) and other
types of carbon credit instruments. In 2007 CERs sold for approximately €15–20/ton
COe2. Iron fertilization is relatively inexpensive
compared to scrubbing, direct injection and other industrial approaches, and can theoretically
sequester for less than €5/ton CO2, 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 6–12% decline
in global plankton production since 1980. A full-scale plankton restoration program
could regenerate approximately 3–5 billion tons of sequestration capacity worth €50-100
billion in carbon offset value. However, a 2013 study indicates the cost versus
benefits of iron fertilization puts it behind carbon capture and storage and carbon taxes.==Sequestration definitions==
Carbon is not considered “sequestered” unless it settles to the ocean floor where it may
remain for millions of years. Most of the carbon that sinks beneath plankton
blooms is dissolved and remineralized well above the seafloor and eventually (days to
centuries) returns to the atmosphere, negating the original benefit.Advocates argue that
modern climate scientists and Kyoto Protocol policy makers define sequestration over much
shorter time frames. For example, trees and grasslands are viewed
as important carbon sinks. Forest biomass sequesters carbon for decades,
but carbon that sinks below the marine thermocline (100–200 meters) is 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 ocean iron fertilization could represent a potent means to slow global warming current
debate raises 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, 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 quantified. Creating phytoplankton blooms in iron-poor
areas is like watering the desert: in effect it changes one type of ecosystem into another. The argument can be applied in reverse, by
considering emissions to be the action and remediation an attempt to partially offset
the damage. Fertilization advocates respond that algal
blooms have occurred naturally for millions of years with no observed ill effects. The Azolla event occurred around 49 million
years ago and accomplished what fertilization is intended to achieve (but on a larger scale).===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. A 2010 study of oceanic transparency since
1899 and in situ chlorophyll measurements concluded that oceanic phytoplankton medians
decreased by ~1% per year over that century.===Ecological issues=======
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 tides 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 open oceans (far from shore) where iron deficiency is substantial. 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
diatom spp., which are generally nontoxic in the open ocean, began producing toxic levels
of domoic acid. Even short-lived blooms containing such toxins
could have detrimental effects on marine food webs.====Deep water oxygen levels====
When organic bloom detritus sinks into the abyss, a significant fraction is devoured
by bacteria, other microorganisms and deep sea animals that also consume oxygen. A large enough bloom could render certain
regions beneath it anoxic and threaten other benthic species. However this would entail the removal of oxygen
from thousands of cubic km of benthic water beneath a bloom and so seems unlikely. 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, that disturb
the food chain impacting whale populations or fisheries is unlikely as iron fertilization
experiments that are conducted in high-nutrient, low-chlorophyll waters favor the growth of
larger diatoms over small flagellates. This has been shown to lead to increased abundance
of fish and whales over jellyfish. A 2010 study showed that iron enrichment stimulates
toxic diatom production in high-nitrate, low-chlorophyll areas which, the authors argue, raises “serious
concerns over the net benefit and sustainability of large-scale iron fertilizations”. Nitrogen released by cetaceans and iron chelate
are a significant benefit to the marine food chain in addition to sequestering carbon for
long periods of time.However, CO2-induced surface water heating and rising carbonic
acidity are shifting population distributions for phytoplankton, zooplankton and many other
populations. Optimal fertilization could potentially help
restore lost/threatened ecosystem services.====Ocean Acidification====
A 2009 study tested the potential of iron fertilization to reduce both atmospheric CO2
and ocean acidity using a global ocean carbon model. The study showed that an optimized regime
of micronutrient introduction would reduce the predicted increase of atmospheric CO2
by more than 20 percent. Unfortunately, the impact on ocean acidification
would be split, with a decrease in acidification in surface waters but an increase in acidification
in the deep ocean.==See also==
Carbon dioxide sink Iron chelate
Ocean pipes Liebig’s law of the minimum
Iron cycle

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