Iron fertilization

cyclopathic · Jun 8, 2011

[ame="http://en.wikipedia.org/wiki/Ocean_iron_fertilization"]Iron fertilization - Wikipedia, the free encyclopedia[/ame]

Iron fertilization is the intentional introduction of iron to the upper ocean to stimulate a phytoplankton bloom. This is intended to enhance biological productivity, which can benefit the marine food chain and remove carbon dioxide from the atmosphere. Iron is a trace element necessary for photosynthesis in all plants. It is highly insoluble in sea water and is often the limiting nutrient for phytoplankton growth. Large 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 in the deep ocean, and to increase marine biological productivity which is likely in decline as a result of climate change. Since 1993, thirteen international research teams have completed ocean trials demonstrating that phytoplankton blooms can be stimulated by iron addition. However, controversy remains over the effectiveness of atmospheric CO2 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.
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The role of iron

About 70% of the world's surface is covered in oceans, and the upper part of these (where light can penetrate) is inhabited by algae. In some oceans, the growth and reproduction of these algae is limited by the amount of iron in the seawater. Iron is a vital micronutrient for phytoplankton growth and photosynthesis that has historically been delivered to the pelagic sea by dust storms from arid lands. This Aeolian dust contains 3â€“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). 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,[25] 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".[26]

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 0.5â€“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.

Previous instances of biological carbon sequestration have triggered major climatic changes, such as the Azolla event. Plankton that generate calcium or silicon 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 plankton blooms, half (or more) is generally consumed by grazing organisms (zooplankton, krill, small fish, etc.) but 20 to 30% sinks below 200 meters (656 ft) into the colder water strata below the thermocline.[citation needed] 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.)
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icarus · Jun 8, 2011

When are going to learn the coss of unintended consequences?

We know what it causing climate change. Every mega project "solution" that I have read abou is fraught with potential disastrous unforeseen environmental consequences. Coming up with these kind of ideas, while they may be a useful execise, just let's us continue our profligate wasting ways.

Get a clue folks, we know how to cure this, and that is to use less fossil fuel,and encourage alternative.

Icarus

tochatihu · Jun 8, 2011

Like all things marine and meteorological, this is an area I understand incompletely.

If you want to go beyond wiki, this article is reasonably readable:

http://www.tos.org/oceanography/issues/issue_archive/issue_pdfs/22_3/22-3_strong.pdf

In short it suggests that the actual C removal (by sinking) looks like a small fraction of the total phytoplankton mass, and there are some indications of unintended consequences. I don't think it shows strong short-term benefits. Nevertheless, I expect the oceanographers to continue experiments. It's kinda what they do.

This article:

http://www.biogeosciences.net/7/1075/2010/bg-7-1075-2010.pdf

is more of a head exploder. Don't say I didn't warn you...

cyclopathic · Jun 9, 2011

icarus said: ↑

When are going to learn the coss of unintended consequences?

We know what it causing climate change. Every mega project "solution" that I have read abou is fraught with potential disastrous unforeseen environmental consequences. Coming up with these kind of ideas, while they may be a useful execise, just let's us continue our profligate wasting ways.

Get a clue folks, we know how to cure this, and that is to use less fossil fuel,and encourage alternative.

Icarus
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We know consequences and still burning up fossil fuels, right?

Yes agree 100% we should tackle the CO2 at source point, not the end result.

However we may be approaching the point that we cannot avoid, and solution to GW has to include some degree of geoengineering.

What is interesting that the Aeolian dust deposition had fallen nearly 25% in recent decades.With 3â€“5% iron content it had had to have effect on phytoplankton growth and CO2 balance.. Don't think models take it into consideration.

Also artic and glacial ice (and anthropogenic activity) contributes to iron balance, is it even in picture?

cyclopathic · Jun 9, 2011

here is some info from IPCC 11.2.2 Ocean fertilization and other geo-engineering options - AR4 WGIII Chapter 11: Mitigation from a cross-sectoral perspective

a body of literature has developed on alternative, geo-engineering techniques for mitigating climate change. This section focuses on apparently promising techniques: ocean fertilization, geo-engineering methods for capturing and safely sequestering CO2 and reducing the amount of sunlight absorbed by the earth’s atmospheric system. These options tend to be speculative and many of their environmental side-effects have yet to be assessed; detailed cost estimates have not been published; and they are without a clear institutional framework for implementation
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Iron fertilization of the oceans may be a strategy for removing CO2 from the atmosphere. The idea is that it stimulates the growth of phytoplankton and therefore sequesters CO2 in the form of particulate organic carbon (POC). There have been eleven field studies in different ocean regions with the primary aim of examining the impact of iron as a limiting nutrient for phytoplankton by the addition of small quantities (1–10 tonnes) of iron sulphate to the surface ocean. In addition, commercial tests are being pursued with the combined (and conflicting) aims of increasing ocean carbon sequestration and productivity. It should be noted, however, that iron addition will only stimulate phytoplankton growth in ~30% of the oceans (the Southern Ocean, the equatorial Pacific and the Sub-Arctic Pacific), where iron depletion prevails. Only two experiments to date (Buesseler and Boyd, 2003) have reported on the second phase, the sinking and vertical transport of the increased phytoplankton biomass to depths below the main thermocline (>120m). The efficiency of sequestration of the phytoplankton carbon is low (<10%), with the biomass being largely recycled back to CO2 in the upper water column (Boyd et al., 2004). This suggests that the field-study estimates of the actual carbon sequestered per unit iron (and per dollar) are over-estimates. The cost of large-scale and long-term fertilization will also be offset by CO2 release/emission during the acquisition, transportation and release of large volumes of iron in remote oceanic regions. Potential negative effects of iron fertilization include the increased production of methane and nitrous oxide, deoxygenation of intermediate waters and changes in phytoplankton community composition that may cause toxic blooms and/or promote changes further along the food chain. None of these effects have been directly identified in experiments to date, partly due to the time and space constraints.
Nitrogen fertilization is another option (Jones, 2004) with similar problems and consequences.
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Iron fertilization

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