Background

Global warming is a growing issue of concern to policy makers and scientists alike. Scientists around the world are investigating options to abate global warming while policy makers are attempting to regulate greenhouse gas emissions without hurting the global economy. As a result of these efforts, cleaner energy technologies have been developed, more energy efficient products have entered the market, and public awareness of energy conservation is increasing. However, atmospheric concentrations of greenhouse gases continue to rise.

Scientists are now investigating the possibilities for enhancing the natural CO₂ sequestration capacity of the earth. CO₂ is sequestered out of the atmosphere through assimilation by plants during photosynthesis. Eventually most of this carbon enters into the global sinks, soil or the deep ocean, in the form of dead or fecal matter.

One method for enhancing CO₂ sequestration in the oceans is by stimulating phytoplankton growth through iron fertilization. Iron fertilization is based on the hypothesis that iron is the limiting nutrient in phytoplankton growth. This is true in the equatorial Pacific Ocean and the Southern Ocean, whereas in other regions different nutrients are limiting. Like adding fertilizer to a garden to help crops grow, iron can be added to the ocean to help phytoplankton grow. By increasing phytoplankton growth, we increase the capacity of the ocean to absorb CO₂, and thus reduce CO₂ concentrations in the atmosphere.

The main proponent of iron fertilization was John Martin of Moss Landing Marine Lab.
Martin carried out a series of in vivo experiments to prove that iron was the limiting nutrient to phytoplankton growth. He and his team filled bottle with water from high-nutrient low-chlorophyll (HNLC) regions and incubated them at light and temperature similar to natural conditions. To half of the bottles iron was added and the other half were used as controls. Phytoplankton abundance and nutrient content were monitored in order to see if the additional iron helped the phytoplankton assimilate the other nutrients. In the end, the iron-enriched bottles had more phytoplankton growth, and decreased nutrient concentrations over repeated experiments, relative to the control bottles.
 

Experiments
Iron Ex. I
Iron Ex. II
SOIREE
Ocean Farming Inc.

Iron Ex. I
Martin believed these experiments proved the iron-hypothesis, and proceeded to design experiments to test the theory of iron fertilization in the open ocean. He calculated that enough iron could easily be added to stimulate phytoplankton growth in a 100 kilometer-squared patch of ocean, dependant on their being enough nitrogen and phosphorous available. Because of the logistical difficulty associated with carrying out such an experiment in the Southern Ocean (due to unpredictable amounts of sunlight), Martin proposed a location in the equatorial pacific as the site for his study. He applied, and received funding for his first experiment, Iron Ex. I, from the National Science Foundation.

Iron Ex. I was done in April of 1993 in order to test if a patch of iron-fertilized ocean could be created and followed. This would be necessary in order to determine if the fertilization was successful. Iron Ex. I was carried out in the equatorial Pacific Ocean, near the Galapagos Islands. During the experiment 7,800 moles of iron (II) sulfate was mixed with 15, 600 liters of seawater and spread over a 64 square kilometer area. It was mixed by natural convection down to 35 meters. Because iron is extremely insoluble, hydrochloric acid was also added to decrease the pH of the water to 2. In order to trace the patch, a tracer chemical was added and 5 buoys equipped with Global Positioning System devices were deployed at the four corners and middle of the patch. The goal was to fertilize this patch of ocean and increase iron concentrations from 1nM to 4 mM.

Iron concentrations in the fertilized patch initially increased to 3.6mM, caused a doubling in the amount of phytoplankton, and a quadrupling in their growth rate. However, after only one day, phytoplankton activity leveled off and iron concentrations steadily decreased, reflecting an apparent net loss of available iron from the system. In addition, only about ten percent of the carbon dioxide was removed from the air compared to what was expected. The experiment was ended prematurely when a less dense low salinity front moved in a pushed the patch down 20-40 meters below the surface.

There are many possible explanations for the unexpected results of this experiment. First of all, along with the increase in phytoplankton was an increase in zooplankton, which consumed the phytoplankton. This would limit phytoplankton activity and the sequestration of CO2. A reason for the decreased concentrations of iron after the first day is that possibly the iron combined with organic material and sunk to the bottom. Other scientists also suspect that other nutrients, such as zinc, may have been limiting phytoplankton growth.

Iron Ex II
A second experiment, Iron Ex II, designed by John Martin was performed in 1995. The same location was chosen for Iron Ex. II as for Iron Ex I. Due to Dr. Martin’s untimely death in 1993, this expedition was lead by his colleague Kenneth Coale, also of MLML. A group of 37 scientists from 13 different institutions in the U.S., Great Britain and Mexico participated in this experiment.

The main improvement of Iron Ex. II over Iron Ex I, is that in this experiment iron was continuously added over a weeks time (on days 1, 3, and 7). This helped maintain a concentration of 2nM, and eliminated the problem of iron depletion. In this experiment, a fertilized patch of 72 square kilometers was created using approximately 1,000 pound of iron. Tracer and hydrochloric acid were also added as in Iron Ex. I. Two additional (24 square kilometer) “control” patches were also created. One  was seeded with tracer and hydrochloric acid only in order to determine the effects of decreased pH on phytoplankton growth. The second patch was fertilized with iron only.

The results of this experiment showed that phytoplankton growth doubled, resulting in two million additional pounds of biomass. Because of the subsequent increase in chlorophyll, the water turned green. Zooplankton grazing also increased, however this only affected the amount of smaller phytoplankton present, as much of the phytoplankton grew very large very fast. CO2 concentrations in the air above the patch decrease 60%, corresponding to the assimilation of 2.3 million kilograms by the phytoplankton.  Nitrate (another nutrient necessary to phytoplankton growth) concentrations also decreased 50% as a result of the increase in phytoplankton activity.

Southern Ocean Iron Release Experiment (SOIREE)
A third experiment, called SOIREE (Southern Ocean Iron Release Experiment) was carried out in 1999. This experiment was sponsored by the National Institute of Water and Atmospheric Research in New Zealand. SOIREE was carried out in the polar Southern Ocean. Like the Iron Ex experiments, iron was used to fertilize a patch of approximately 50 square kilometers. Iron was added 4 times over a 13 day period in order to maintain raised iron concentrations. The response of the system was slow in comparison to the Iron Ex experiments. Not until 5 days after the initial release were increased levels of phytoplankton observed. It was also observed that dissolved nutrient and CO2 concentrations decreased.

Ocean Farming Inc.
Ocean Farming Inc. (OFI) was established by a group of private investors and the chemical engineer and entrepreneur Michael Markels in 1995. Markels ideas for ocean farming were the first of their kind to ever apply for a patent and were therefore approved in 1994. OFI has leased the rights to 800,000 square miles of the exclusive economic zone of the Marshall Islands, a small pacific island nation, for $3 million a year in order to carry out ocean farming experiments.

Inspired by the Iron Ex. experiments, Markels designed a system for automatic slow release of iron and other nutrients into the oceans photic zone. The system consists of buoyant chemically protective containers full of nutrients, which are released slowly over time. Like the Iron Ex. experiments, It is expected that by increasing the amount of necessary available nutrients, phytoplankton growth will be stimulated. OFI hopes this increased growth of phytoplankton will not only sequester more CO2 from the atmosphere, but also stimulate  increased production throughout the food chain.

Markels has estimated that farming just 100,000 square miles could sequester up to one-third of the carbon dioxide released by the U.S. into the atmosphere. Markels estimates that if ocean farming were conducted within the  U.S. 200 mile exclusive economic zone in the Gulf Stream along the Atlantic coast, fish production could be increased from 125,000 to 5 million tons per year. This increase would be worth $40 billion (with an initial cost of only $100 million per year) and provide half a million jobs to the U.S. economy. It would also revitalize our declining fishing industry, generate increased supplies of a high-protein food, and decrease atmospheric CO2.
 

Concerns about Iron Fertilization
Biological concerns
Chemical concerns
Ocean circulation
Climate
“Natural” fertilization
Ethical Issues

Because so few experiments on iron fertilization have been conducted, there are still many uncertainties associated with the long-term effects. While the short term effects on phytoplankton growth and carbon sequestration seem positive, little is known about how the entire ecosystem would be affected by iron fertilization. Many hypotheses seem to overlook the true complexity of the ecosystem. Before large-scale iron fertilization projects can be pursued, many questions about the long term chemical and biological impacts must be answered and details of the actual cost effectiveness should be investigated.

Biological concerns

• Effects of increased iron concentrations (and the associated decrease in pH) on other organisms

We cannot say with any certainty what the effects of increased iron concentrations (and the associated decrease in pH) would have on other organisms. Some organisms are highly intolerant of such changes in their environment and therefore would not be able to survive. This would also effect the overall biodiversity and continuity of the food chain.

• Decreased productivity of deeper algal growth

Increased phytoplankton mass in the surface waters would decrease the depth to which light penetrates, upsetting deeper algal growth and productivity.

• Inhibition of zooplankton productivity

During Iron Ex II it was observed that zooplankton feeding was inhibited because iron fertilization caused larger species of phytoplankton to become dominant. This effect would therefore alter the food chain by promoting the growth of larger phytoplankton and inhibiting zooplankton production.

•  Decreased overall biodiversity

It has been observed in the past that there is a correlation between algal blooms and decreased biodiversity, and it has been hypothesized that prolonged increased phytoplankton growth may have the same effects. Many of the above factors could contribute to decreased biodiversity by selecting for the stronger species.

•  Impact on the food web

Any changes to biodiversity or species abundance will have tremendous effects on the food web. Iron fertilization will most likely cause changes in phytoplankton species composition. By decreasing the  availability of some organisms, other organisms that use them as a food resource will also suffer.

Chemical concerns

• Depletion of other nutrients

Increased phytoplankton productivity may deplete other essential nutrients and cause them to become limiting to phytoplankton growth. This in turn would cause a decline in the rate of Carbon Dioxide sequestration

• Changes in elemental cycling

As more nutrients are consumed, large quantities of them will enter into circulation, possibly overwhelming other aspects of the cycle. For example, there might be an increased cycling of nitrogen and evolution of N2O (a byproduct of denitrification) because of increased microbial activity in the deep ocean.

• Anoxic deep ocean/Methane production

There are concerns about the added biomass in the deep ocean consuming all available oxygen and creating anoxic conditions in the deep ocean. This would also stimulate the production of methane, which is a potent greenhouse gas.

• Dimethyl Sulfide

Another concern is increased atmospheric concentrations of dimethyl sulfide, which is released from phytoplankton growth. In the atmosphere, dimethyl sulfide oxidizes to form sulfate aerosols, which after the greenhouse gases, exert the next largest influence on climate. The sulfate aerosols can cause an increase in cloud cover when present in significant quantities in the atmosphere. This in turn affects the amount of radiation absorbed by the atmosphere and can cause a cooling in the earth’s mean temperature.

Ocean Circulation

• Carbon possibly only temporarily sequestered

It is possible that the observed sequestration during the Iron Ex. experiments was only temporary, because long-term observations were not made. The carbon may not have been effectively removed, but only absorbed temporarily and the re-released later. Therefore, as dissolved carbon levels increased in the ocean mixed layer, the carbon would largely be returned to the atmosphere.

• Upwelling of stored carbon

Carbon stored in the deep ocean will eventually re-circulate and, through upwelling to the surface, be released to the atmosphere.

• Upwelling/Downwelling of patch

Ocean circulation patterns may affect the size and integrity of the fertilized patch, as up-and down-welling cause mixing and sinking.

Climate

• Change in planetary albedo

An increase in phytoplankton biomass could affect the planetary albedo, because phytoplankton have a different reflectivity than water. This could cause additional effects on climate by causing more or less reflection the sun’s rays.

• Change in mean oceanic temperatures

Changes in mean oceanic temperature could also affect the effectiveness of fertilization. The ocean-atmosphere interface is highly temperature dependent for absorbing Co2. A rise in mean ocean temperature might offset the effectiveness of fertilization because it would decrease the amount of CO2 that could be dissolved.

• Changes in net flux of greenhouse gases

Because iron fertilization would only be effective in certain regions, other parts of the ocean may experience different changes in the flux of greenhouse gases. Possibly, this could also lead to anoxia in some regions.

“Natural” fertilization

• Deep Sea Volcanic activity

There are also potential natural sources of iron fertilization.  One of these is undersea volcanic activity. Deep ocean hydrothermal vents pump large quantities of iron rich water into the ocean. If shifts in hydrothermal activity deep within the ocean occur, this iron may be introduced into the portions of the ocean that are iron deficient and a natural bloom may take place.

• Changes to desert area

If significant changes occur to the area of earth’s deserts they could contribute a higher concentration of iron dust to the atmosphere, which would similarly act to naturally fertilize the ocean.

• Deep ocean iron beds

There is also concern about the natural feedback mechanisms by which the effects of iron fertilization may be amplified. Altering phytoplankton growth might also alter algae growth, which might in turn affect deep ocean iron beds, causing an increase in  concentrations of iron and further amplifying phytoplankton growth. Such a unstable scenario could possibly send us back to an ice age.

Ethical Issues
Finally there are also ethical issues surrounding the topic of iron fertilization. Much of the damage that has been done to our environment is a result of numerous technological advances and industrial expansion in the last century. It was inevitable that at some point man would try and counteract some of the damage we have inflicted on our environment via more technology. Whether or not iron fertilization is ethically correct is an important question for scientists and policymakers alike to consider. Hopefully the answer will become clearer as the true risks of this technology are revealed.
 

Policy Issues
Need for Policy
Experiment Evaluation
Current Policy
Policy Evaluation Criteria

The rate of technological advances in iron fertilization exceeds the rate of policy development. Because of this,  it is necessary for the current issues and uncertainties to be evaluated so that regulations on iron fertilization practices can be put into effect. Without some kind of regulations from government, independent research and experimentation has free reign over the oceans, which are a common resource for all.

Need for Policy
Iron fertilization is a proposal with very high economic risks. If the long-term effects of iron fertilization were bad, it could have a horrible impact on the global economy. Many concerns have been raised about:

• Intergenerational rights and stakeholder equity with respect to common marine resources.
• Who is legally liable? Because the oceans are a common resource (outside of each country’s exclusive economic zone), who (individual, country, etc.) is legally responsible for protecting the oceans or for prosecuting those who abuse it?
• Potential costs and benefits are possibly not accurately represented in proposals, because of insufficient data to make such estimates.
• Media represents the prospect as overly optimistic and selectively reports peer-reviewed facts, contributing to premature legitimization of iron fertilization
• Governments of poorer countries are unaware or willfully ignorant of the potential negative impacts.

• Is the experiment designed with full and appropriate consideration of existing scientific knowledge?
• Is the scale, both in regards to area and duration, appropriate for the experiment?
• Does the experiment lend itself to “life cycle” accounting of all the components involved in the fertilization?
• What should be measured and how well?

In the future, it is possible that International governments will establish a system of Carbon taxes and credits in order to regulate worldwide CO₂ emissions. Therefore, the question arises of whether or not sequestration could count against a country’s used credits. The Lazio Bill, under legislative review in the U.S., could set a precedent for such domestic carbon management guidelines and standards. This bill supports actions that lead to “actual reductions in greenhouse gas emissions or actual increase in net carbon sequestration.” This bill would also grant a reduction in the amount of carbon credits claimed equal to the amount of CO₂ sequestered. However, in order to qualify for such reductions, adequate scientific monitoring must be completed to prove the amount of carbon sequestered. Much more scientific research on the effectiveness of iron fertilization would be needed in order to meet these criteria.

Policy Evaluation Criteria
In order to evaluate whether or not policy will effectively regulate iron fertilization, the following questions must be considered:

• Who are the stakeholders?
• How should the costs and benefits be determined?
• Do we have enough scientific evidence to make a decision?
• Have all sides of the issue been considered?
• How should uncertainties be treated?
• What is the role of “expert” judgement in decision making on this issue?
• What kind of monitoring standards should be required once a policy is implemented?