Case Teaching Notes
for
“Is Iron Fertilization Good for the Sea?”

by
LeLeng To
Department of Biological Sciences
Goucher College

Introduction

This case would be appropriate for introductory biology, ecology, environmental biology, microbiology, and environmental microbiology classes, as well as courses dealing with environmental policy. Prior knowledge about greenhouse gases and global warming would be useful, although these concepts can be assigned along with readings for the case study.

Objectives

Specific objectives may include the following:

Classroom Management

This case was originally designed for classes of 12 to 18 students that meet for 50 minutes. This time constraint necessitates teaching the case study over two or more class meetings.

First Meeting

The first meeting is divided into:

If a debate is the venue for learning, then students are divided into groups that take the view of a specific stakeholder. The stakeholders include:

Members of the groups pick roles as timer-keeper, reporter, devil’s advocate, and group leader, who must take the view of the assigned stakeholder.

If task forces are created, then members of the group take on the roles of Luis Marbles, Kate Cheshire and scientists involved in the iron fertilization experiments, a scientist concerned about ecosystem-scale experiments, and a government/policy person.

You will notice that in either debate or task forces the groups consist of four members. For larger classes, task forces may have more members representing more stakeholders.

Second Meeting

For the task force format, each member of the task force comes prepared with an assigned reading and each group spends 20 minutes discussing issues. At the end of the 20 minutes, task force reporters take turns to state their groups’ policy and provide supporting scientific arguments. After hearing all presentations, students are asked to write a very short paragraph (5-minute paper) on what they have learned regarding greenhouse gases, iron fertilization experiments, etc., and how the discussions may have altered their position regarding iron fertilization and ocean farming. The results of the 5-minute papers are discussed in the following meeting, which will also be used to raise unanswered questions and anything else that needs further clarification.

For the debate format, each member of the debate group comes prepared with an assigned reading and each group spends 20 minutes discussing the best ways to present their viewpoint. At the end of 20 minutes, debate team representatives take turns to state their team’s policy and supporting arguments. After hearing all presentations, each debate team meets for another 10 minutes to discuss concessions or additional arguments. The remaining class meeting is used to present any alterations in positions or additional arguments. If time permits, each student writes a 5-minute paper on what he or she has learned from the group activities, which is a way to assess student learning and student perception of learning through group activities.

Blocks of Analysis

Greenhouse Gases and Effects

Greenhouse gases are atmospheric gases that trap heat. Some greenhouse gases, including water vapor, carbon dioxide, methane, nitrous oxide, and ozone, occur naturally. Human activities add to the level of these gases. In addition to respiration, the burning of fossil fuel and various land uses generate CO2. Deforestation, biomass burning, agricultural expansion, heating of homes and workplaces, electric power generation, transportation, urbanization, and industrial combustion all contribute to atmospheric carbon dioxide levels. At the present level of fuel use, approximately six billion tons of carbon dioxide per year are being added to the atmosphere. The shifts from forest to urban or suburban use have increased atmospheric CO2 directly as described above and indirectly by decreasing carbon dioxide fixation by plants. For three-quarters of a century, scientists have been aware of CO2 accumulation, which became dramatic after the industrial revolution. The overwhelming concern is that more carbon dioxide will trap more heat in the earth’s atmosphere. Since this heat retention is analogous to the glass panes of greenhouses, this is called the greenhouse effect. Like glass panes, CO2 lets sunlight in to warm the earth. At night, heat radiates away from the earth but CO2, just like greenhouse glass panes, retards the rate of heat radiation from the earth.

Methane is emitted during the production and transport of coal, natural gas, and oil; by the decomposition of organic wastes in landfills; and by the raising of livestock. Methane from livestock and landfills really comes from methanogenic bacteria. Dietary components can increase the methane gas emissions from cows. Methane also can be produced wherever there are anaerobic conditions such as flooded rice paddies. As a greenhouse gas, methane traps over 21 times more heat than carbon dioxide.

Nitrous oxide is released during agricultural and industrial activities, by the burning of solid wastes and fossil fuels, and by microbial activities. Nitrous oxides retain 270 times more heat than carbon dioxide.

Refrigeration, air conditioning, and the by-products of foam production contain non-natural greenhouse gases such as hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and chlorofluorocarbons (CFCs or Freon), which are also used as solvents and spray-can propellants. These substances are far more effective than CO2 at heat retention, with HFCs and PFCs being the most heat-absorbent. A rare manufacturing product, SF5CF3, represents the most potent greenhouse gas ever detected. Black soot from industrial smoke traps heat since black absorbs sunlight. Although black soot emissions have almost disappeared from Western industry, a great deal of soot is produced by unregulated industry and through the use of fires for cooking and heating in unelectrified homes in developing countries.

Although this is an uncomfortable issue for many, overpopulation is an increasingly significant factor. The geometric increase in population size and the resultant increase in human activities contribute to the greenhouse effect. This leads to carbon dioxide production faster than can be used by photoautotrophic organisms, such as phytoplankton and plants. Barring unforeseen volcanic activities that generate massive amounts of dust that reflect sunlight away from the earth, most scientists agree that there will be a gradual warming trend and the sea level will gradually rise.

The burgeoning human population has created a carbon imbalance. There can be no discussion of global warming without considering the human population problem. We are changing the chemical, biological, and physical structure of the earth. Since the beginning of the industrial revolution, atmospheric concentrations of carbon dioxide have increased by almost 30 percent, methane levels have doubled, and nitrous oxide concentrations have increased by about 15 percent. We have altered almost 50 percent of the earth’s surface by filling wetlands, converting tall grass prairies to cornfields, and converting forests to urban and suburban areas. We have doubled environmental nitrogen by excessive use of fertilizers and the burning of fossil fuel. We have accelerated extinction rates 1000-fold through human-induced planetary changes, primarily through habitat loss and crowding out of native species on land and through over-fishing. If we continue on this path, about one-third to two-thirds of animal and plant species will be lost by the second half of this century. Unlike natural mass extinctions, human-induced extinction is happening at a rapid rate, measured in hundreds of years, not hundreds of thousands or millions of years.

Global warming will exacerbate these effects as human activities continue to increase atmospheric concentrations of greenhouse gases. In the past century, the world has warmed by up to 1.1 degree Fahrenheit (0.6 degree Celsius) and the rate of warming has accelerated in the last quarter-century. Since scientists began recording about 150 years ago, the seven warmest years occurred in the past decade with 1998 as the warmest. Every month from January to August in 1998 broke the previous record for that month. At the rate of increase over the last few decades, by the year 2050, carbon dioxide levels will double that of pre-industrial times and cause a further warming of 1.8 to 6.3° F (1 to 3.5° C) over this century.

Global Warming and Its Detrimental Effects

Global warming is expected to melt more glacier ice, raise sea levels, and change regional climate conditions. With increasing frequencies and intensities, some areas will be affected by droughts while other areas will be affected by rainfall. Imagine the damage due to dry soil from droughts and landslides from heavy rainfall. Altering local climate could:

  1. alter crop yields, forest, and water supplies;
  2. pose potential health hazards to humans, other animals, and plants; and
  3. affect ecosystems and their distribution.

The landscape of some of our national parks may change irreversibly. Deserts may expand into rangelands. Changing the nature of habitats in such a short period of time could result in species extinction and decreased biological diversity.

Extant corals are very sensitive to warm temperatures. Although paleontonlogical evidence indicates that past corals survived temperature changes and evolved from warm-temperature forms to cold-adapted species, there is no way to predict the viability of present-day coral reefs if the water temperatures warm too fast. Although global warming does not cause El Niños, the effect of El Niño on coral bleaching serves to illustrate the potential dangers of global warming. El Niño is a disruption of the ocean-atmosphere system in the tropical Pacific having important consequences for weather and climate around the globe. This disruption increases rainfall across the southern tier of the United States and in Peru, causing destructive flooding, and drought in the West Pacific. Devastating brush fires in Australia have been attributed to El Niño. El Niño warms ocean waters, killing the dinoflagellate symbionts within corals. Calcium deposition in coral building is dependent on dinoflagellates. Without dinoflagellates, the corals are bleached, incapable of further growth.

El Niños have been around for hundreds if not millions of years. Some scientists suggest, however, that warmer global sea surface temperatures can enhance the El Niño phenomenon. In recent decades, El Niños have been more frequent and more intense. It has been suggested that the combined effects of warming, human activity, and pollution may be contributing to the recent rise in life-extinguishing disease outbreaks in aquatic ecosystems (Science September 3, 1999).

We cannot predict what other life forms will be endangered by global warming. And we do not know the effect of decreased diversity on our environmental health. There are compelling scientific and economic reasons to maintain biological diversity. All organisms are part of a community structure and food web. We do not have the knowledge to foresee far-reaching effects of the loss of a particular species or group of species. Microbes, plants, and animals provide us with drugs, food, and raw materials for industry. About a quarter of prescription drugs in the United States contain plant or microbial extracts that cannot be synthesized de novo. Aside from these pragmatic reasons, there are philosophical and moral arguments to consider. As a species, we are newcomers to the earth, yet we have the power to alter habitats, leading to the extinction of some species and undesirable proliferation of others (e.g., Zebra mussels, the killer alga Caulerpa taxifolia).

Another potential danger of global warming is the redistribution of the habitats of arthropod vectors of diseases, which in turn could contribute to the accelerated spread of infectious disease. Encephalitis, dengue, malaria, and yellow fever could become common in areas outside the tropics. Some scientists suggest that the faster rise in nighttime temperatures over daytime temperatures is heightening the spread of infectious diseases because the range of arthropod vectors is mainly limited by nighttime temperatures. In September 1999, three elderly people died in New York City from the St. Louis viral encephalitis, which is also transmitted by mosquitoes. Some scientists suggest that the incidence of the West Nile Virus encephalitis in the United States may be the result of global warming. The mild winter allowed more mosquitoes to survive in sewers, damp basements, and other sources of stagnant waters. The dry spring and summer in 1999 caused organic compounds to concentrate in evaporating water sources that then nourished mosquito larvae. The lack of rain killed frogs, lacewings, and ladybugs, which are the predators of mosquitoes. Whether the virus entered the U.S. via mosquitoes, birds, or people is not known. What is known is that the heat allowed rapid proliferation of the virus within mosquitoes. Birds congregating around dwindling water sources were bitten by mosquitoes and infected with the West Nile virus. These interactions amplified viral proliferation and increased the probability of the infection spreading to people. In 1999, seven people died of the West Nile virus. This July 2000, mosquitoes carrying the virus and birds with the disease were found again.

Global warming is expected to change the frequency, timing, intensity, and duration of extreme weather phenomena such as tornadoes, hurricanes, and extremely heavy rainfall. Direct results are injury and death. Flooding from hurricanes and the rise in sea level can contaminate drinking water. Globally, the mean sea level rose at a rate of about 1 to 2 mm/year, resulting in a 10 to 25 cm increase over the last century. This rate of increase is significantly greater than the rate averaged over the past thousand years. Diarrheal disease kills three million children annually. In developing countries, water-borne diseases account for 90 percent of deaths due to infectious diseases. In a warmer, more polluted, and crowded planet, these diseases will only become more prevalent. After examining hospital admissions of Peruvian children ages 10 or younger, scientists found a strong correlation between increased temperatures and the incidence of childhood diarrhea. In 1997–1998 when the El Niño weather condition resulted in mean temperatures 9°F (5°C) higher, the incidence of diarrheal disease was 200 percent higher in July, August, and September, the coldest months in Peru.

During 1995 and the El Niño year of 1997–1998, which some scientists link to global warming, heat waves caused thousands of additional deaths in India and hundreds in central Europe and the U.S. During the same period, extreme droughts caused forest fires in Florida, California, Central America, Mexico, the Mediterranean region, and Asia. In Southern Asia, the delayed monsoons, compounded by regional farming practices, resulted in prolonged fires, which led to extensive loss of wildlife and widespread respiratory diseases. Meanwhile, floods along the Pacific Coast and southern Brazil led to cholera outbreaks in parts of Latin America. In the wake of Hurricane Mitch, Central America experienced upsurges in cholera, dengue fever, and malaria. In 1997, flooding in Africa also resulted in increased incidence of cholera, malaria, and Rift Valley fever. In addition to health detriments, the increased growth of fungi during floods and increased populations of whiteflies, locusts, and rodents damaged agriculture.

Scientists do not agree about global warming. Some scientists attribute the melting of the North Pole and Antarctic ice caps to global warming. Comparing submarine data in the 1950s and 1960s with 1990s observations, NASA research scientists at the Goddard Space Science Institute found a 45 percent thinning of the ice cover over the entire Arctic basin. Satellite images revealed shrunken ice coverage. However, the lack of ice at the North Pole may not necessarily be related to global warming. The Arctic temperatures in the winter have risen 11°F in the last 30 years and the late 20th century was the warmest in four centuries. In recent decades, the ice pack over the entire Arctic Ocean shrunk in area and thickness but climatologists are still not sure whether declining polar ice stems from a short-natural cycle or represents possible drastic climatic consequences of an industrial civilization’s release of greenhouse gases. Comparing measurements of ice thickness between 1958 and 1976 with data from 1993 and 1997, Dr. Drew Rothrock at the Applied Physics Laboratory of the University of Washington in Seattle found that the thickness decreased from 10.2 ft to 5.9 ft. The decrease was widespread in the central Arctic Ocean. Dr. Claire Parksinson, a climatologist at Goddard Space Flight Center, examined satellite data since the 1970s and reported that Arctic ice cover had been retreating on an average of one-quarter percent per year. However, she is reluctant to make projections into the future based on only two to three decades of observations. There are fluctuations up and down. The retreat was striking in the 1980s but the ice rebounded in the 1990s. However, scientists on the July 2000 Yarmal expedition to the North Pole encountered an unusual amount of water all the way up and that is a reason for concern. In models of climate patterns, scientists suggested that the Arctic would be affected earlier and more seriously than the Antarctic region.

The Iron Hypothesis and Iron Fertilization Experiments

About 20 percent of the earth’s oceans have high macronutrient concentrations of nitrates, phosphates, and silicates, yet have lower than expected primary productivity. Such waters, called HNLC (for high in nitrate and low in chlorophyll), are found in the eastern equatorial Pacific, the subarctic Pacific, and the Southern oceans. For years, there was a controversy regarding the explanation for this low productivity. There were three schools of thought: (1) the iron hypothesis, (2) zooplankton grazing, and (3) the ecumenical hypothesis, which combined the two previous concepts.

Moss Landing Marine Laboratory’s (MLML) John Martin (now deceased) was the chief proponent of the iron hyposthesisthe notion that limiting quantities of iron reduces the primary productivity in the Eastern Equatorial Pacific, the Antarctic Pacific, and the Southern Ocean. This view is consistent with Liebig’s law, which holds that the rate of a chemical reaction is limited by the lowest concentration of any component of the reaction. In biological systems, iron is found in cytochromes and iron-sulfur proteins that mediate electron transfers during the light reactions of photosynthesis and during respiration. It is also a cofactor in other enzymes.

Martin was wont to say, “Give me half a tanker of iron and I’ll give you an ice age.” His development of super-clean collecting methods allowed his team of researchers to show that iron is limiting in these waters. In carbon studies of samples collected from these oceans, adding iron boosted productivity. However, these containment systems do not mimic natural conditions.

In 1993, IronEx I, headed by Martin, introduced iron sulfate into a 64-square-kilometer patch of ocean south of the Galapagos. This single addition of iron resulted in an increase of iron concentration from 0.4 nM to about 4 nM. Although the increase in iron resulted in a two-fold increase in phytoplankton biomass, a three-fold increase in chlorophyll content, and a four-fold increase in photosynthesis, there was a minimal (about 10 percent) decrease in surface CO2 content. The third day after iron infusion, there was little net export of carbon from the inorganic pool, indicating that after a brief disequilibrium, the ecosystem recycled carbon rapidly back into the inorganic form.

The ocean is a major absorber and contributor of atmospheric carbon dioxide. The direction of the gaseous flux is influenced by ocean CO2 concentrations. Photosynthesis, which results in carbon dioxide fixation, decreases atmospheric carbon dioxide. The single addition of iron did not persist in the photic zone of the ocean.

The experiment ended prematurely when less dense water flowing over the experimental patch sank the iron-amended layers to lower regions. What IronEx I provided clearly was support for the iron hypothesis—lack of iron impairs phytoplankton photosynthesis in HNLC waters, resulting in a marked reduction in the efficiency by which light is converted photochemically to stored chemical energy.

After Martin’s death, Kenneth Coale of MLML led a team of 37 scientists from 13 different institutions of the U.S., Great Britain, and Mexico in the 1995 IronEx II study of repeated iron infusions on primary productivity and CO2 levels. Iron sulfate was dispensed on days 1, 3, and 7 to attain and maintain iron concentrations of 2 nM. As in IronEx I, sulfur hexafluoride was used as a tracer. In addition to the experimental patch of 72 square kilometers, two patches—each 24 square kilometers in area—were seeded as controls. One control consisted of seeding with ocean water of the same acidity and the tracer minus the iron sulfate. This control was to determine any effects of transient lowering of pH, introducing the fairly inert hexafluoride, and the presence of a research vehicle on surface life forms. Patch 3 received a single low level iron (to 0.3 nM) and SF4 to mimic the equatorial undercurrent that upwells into surface waters. Repeated surveys of the experimental patches after iron additions showed the following results:

Michael Markels and Ocean Farming Inc. (OFI)

Inspired by the IronEx studies, the chemical engineer Michael Markels established Ocean Farming Inc. to profit commercially from iron-induced phytoplankton blooms. OFI has signed an agreement with the government of the Marshall Islands for private property rights to the 800,000 square miles of ocean around the archipelago. For a sliding yearly fee of $3 million or less, depending on the size of ocean area used, OFI will have the commercial rights to ocean products. OFI conducted studies in the Gulf of Mexico to determine the best way of delivering trace elements, but the results of these studies have not been published. Markels proposes to package iron, phosphate, and key trace elements in buoyant time-release capsules and seed the ocean continually. Through this approach, he hopes to mimic the iron upwelling off the coast of Peru and increase fish populations sufficiently for ocean farming. He estimates that the boost in primary productivity in a 100,000-square-mile area of iron-enriched ocean should fix enough CO2 to counteract the emissions of the U.S. by one-quarter to one-third.

None of the IronEx studies were of the magnitude and length suggested by Markels. Since phytoplankton species do not all bloom in a similar fashion with iron enrichment, it is difficult to predict with any certainty what species will bloom. In both IronEx I and IronEx II, the bloom consisted predominantly of pennate diatoms while a major component of the picophytoplankton, Prochlorococcus, actually decreased in numbers. The specter of 100,000 square miles of toxin-producing harmful algal blooms (HABs) concerns scientists. There is some evidence that diatoms may clog animal gills. Brood sizes of copepods on a diatom diet are actually smaller. Furthermore, surface algal blooms may cut off light and oxygen to subsurface layers. Anaerobic conditions can favor methanogenesis and methane is another greenhouse gas. Sallie Chisholm of the Department of Civil and Environmental Engineering at MIT has also pointed to the long evolutionary history of the upwelling systems. She is skeptical that the system can be easily mimicked.

One of the scientists central to IronEx I has now teamed up with Markels in the commercial venture.

Answer Key

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Supplemental Materials

  1. Biogeochemical Cycling of Carbon from “Unit 5: Fate of the Earth: The Balance of Nature,” in Planet Earth and the New Geosciences: The Web Textbook, V.A. Schmidt and W. Harbert, Dept. of Geology and Planetary Science, University of Pittsburgh.

    Figure 1. Biogeochemical Cycling of Carbon

  2. Greenhouse Gas Emissions from http://www.epa.gov/climatechange/index.html

    Figure 2. 1995 Greenhouse Gas Emissions per Capita

    Figure 3. 1997 Greenhouse Gas Emission by Gas

    Figure 4. Absolute Changes in Greenhouse Gas Emissions in the US

    Figure 5. Percent Annual Change in US Greenhouse Gas Emissions

    Figure 6. U.S. Greenhouse Gas Emission by Gas

    Figure 7. 1997 U.S. Greenhouse Gas Emissions by Sector

  3. The Greenhouse Effect from http://www.epa.gov/climatechange/index.html

    Figure 8. The Greenhouse Effect

  4. Global Temperature Changes from http://www.epa.gov/climatechange/index.html

    Figure 9. Global Temperature Changes

  5. Weather and the West Nile Virus

    See the diagram entitled “Weather and the West Nile Virus” originally published in the Aug. 2000 issue of Scientific American in “Is Global Warming Harmful to Health” by P.R. Epstein (p. 56). The diagram depicts a “possible explanation for how a warming trend and sequential weather extremes helped the West Nile virus to establish itself in the New York City area in 1999.” Although the diagram cannot be reproduced here because of copyright restrictions, it can be accessed online at http://www.sciam.com/article.cfm?colID=1&articleID=0008C7B2-E060-1C73-9B81809EC588EF21 (Also available on author’s website at http://chge.med.harvard.edu/about/faculty/journals/sciam.pdf.).

References

  1. Iron as a limiting factor for phytoplankton productivity

    Martin, J.H. and S.E. Fitzwater. 1988. Iron deficiency limits phytoplankton growth in north-east Pacific subarctic. Nature 331: 342–243.

    Martin, J.H. et al. 1989. VERTEX: phytoplankton studies in the Gulf of Alaska. Deep Sea Research 36: 649–680.

    Martin, J.H. et al. 1990. Iron deficiency limits phytoplankton growth in antarctic waters. Global Biogeochemical Cycles 4: 5–12.

    Martin, J.H. et al. 1990. Iron in Antarctic waters. Nature 345: 156–158.

    Banse, K. 1991. Iron availability, nitrate uptake, and explorable new production in the subarctic Pacific. Journal of Geophysical Research 96: 741–748 (This paper presents a reinterpretation of the data in the VERTEX paper).

    Gordon, R.M. et al. 1997. Iron distribution in the equatorial Pacific: implications for new production. Limnology and Oceanography 42: 419–431.

    LaRoche et al. 1995. Flavodoxin expression as an indicator of iron limitation in marine diatoms. J. Phycology 31: 520–530.

    McKay, R.M. et al. 1999. Accumulation of ferrodoxin and flavodoxin in a marine diatom in response to Fe. J Phycology 35: 510–519.

  2. Grazing control

    Miller, C.B. et al. 1991. Grazing control. Limnology and Oceanography 36: 1600–1615.

    Frost, B.W. 1991. The role of grazing in nutrient-rich areas of the open sea. Limnology and Oceanography 36: 1616–1630.

    Price, N.M. et al. 1994. The equatorial Pacific ocean: Grazer-controlled phytoplankton in an iron limited ecosystem. Limnology and Oceanography 35: 652–662.

  3. Iron-enrichment bottle experiments

    Martin, J.H. and S.E. Fitzwater. 1988. Iron deficiency limits phytoplankton growth in north-east Pacific subarctic. Nature 331: 342–243.

    Banse, K. 1990. Does iron really limit phytoplankton production in the offshore subarctic Pacific? Limnology and Oceanography 35: 772–775. (Banse questions the interpretations of the data reported in the Martin and Fitzwater paper, see reference immediately above)

    Martin, J.H. et al. 1990. Yes, it does: A reply to the comment by Banse. Limnology and Oceanography 35: 775–777.

    Zettler, E.R. et al. 1996. Iron-enrichment bottle experiments in the equatorial Pacific: responses of individual phytoplankton cells. Deep Sea Research II 43: 1017–1029.

  4. IronEx I

    The iron hypothesis: Basic research meets environmental policy, Sallie W. Chisolm, Department of Civil and Environmental Engineering, and Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts
    http://www.agu.org/revgeophys/chisho00/chisho00.html

    Banse, K. 1995. Community response to IRONEX. Nature 375: 112.

    Kolber, Z.S. et al. 1994. Iron limitation of phytoplankton photosynthesis in the equatorial pacific ocean. Nature 371: 145–149.

    Martin, J.H. et al. 1994. Testing the iron hypothesis in ecosystems of the equatorial Pacific ocean. Nature 371: 123–129.

    Watson, A.J. et al. 1994. Minimal effect of iron fertilization on sea-surface carbon dioxide concentrations. Nature 371: 143–149.

    Sakamoto, C.M. et al. 1998. Surface seawater distributions of inorganic carbon and nutrients around the Galapagos Islands: results from the PlumEx experiment using automated chemical trapping. Deep Sea Research II 45: 1055–1071.

  5. IronEx II

    The iron hypothesis: Basic research meets environmental policy, Sallie W. Chisolm, Department of Civil and Environmental Engineering, and Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts
    http://www.agu.org/revgeophys/chisho00/chisho00.html

    Frost, B.W. 1996. Phytoplankton bloom on iron rations. Nature 383: 475–476. (excellent summary of principal results from IRONEX II)

    Moanastersky, R. 1995. Iron surprise: algae absorb carbon dioxide. Science News 148: 53.

    Coale, K.H. et al. 1996. A massive phytoplankton bloom induced by an ecosystem-scale iron fertilization experiment in the equatorial Pacific ocean. Nature 383: 495–501.

    Behrenfeld, M.J. et al. 1996. Confirmation of iron limitation of phytoplankton photosynthesis in the equatorial Pacific ocean. Nature 383: 508–510.

    Cooper, D.J. et al. 1996. Large decrease in ocean-surface CO2 fugacity in response to in situ iron fertilization. Nature 383: 511–513.

    Turner, S.M. et al. 1996. Increased dimethyl sulphide concentrations in seawater from in situ iron enrichment. Nature 383:513–517.

    Cavender-Bares, K.K. et al. 1999. Differential response of equatorial Pacific phytoplankton to iron fertiization. Limnology and Oceanography 44: 237–246.

  6. Southern Ocean Iron Release Experiment

    Southern Ocean Iron Release Experiment (Soiree)
    http://tracer.env.uea.ac.uk/soiree/index.html

  7. Greenhouse gases and global warming

    Global Warming Frequently Asked Questions (NOAA)
    http://www.ncdc.noaa.gov/ol/climate/globalwarming.html

    EPA’s Climate Change Site
    http://www.epa.gov/climatechange/index.html

    Global Warming Will Stop at Nothing, Researcher Predicts (Environmental News Network, February 25, 2000)
    http://www.enn.com/enn-news-archive/2000/02/02252000/hothealth_10326.asp

    Global Warming Spells Health Warning (Environmental News Network, July 15, 2000)
    http://www.enn.com/enn-news-archive/2000/07/07152000/epstein_14753.asp

    N.Y. Disease Outbreak Called a Global Warning (Environmental News Network, September 21, 1999)
    http://www.enn.com/enn-news-archive/1999/09/092199/encep_5776.asp

    Extreme Weather’s Effect on Health Measured (Environmental News Network, February 16, 1999)
    http://www.enn.com/enn-news-archive/1999/02/021699/health_1677.asp

    Climate Change Propels Plague, Study Says (Environmental News Network, November 25, 1999)
    http://www.enn.com/enn-news-archive/1999/11/112599/plaque_7615.asp

    Global Warming May Harm Human Health (Environmental News Network, November 13, 1998)
    http://www.enn.com/enn-news-archive/1998/11/111398/climatehealth_184.asp

    Scientists Warn of Mass Extinction (Environmental News Network, August 3, 1999)
    http://www.enn.com/enn-news-archive/1999/08/080399/extinction_4759.asp

    Pollution, Warming Spur Marine Diseases (Environmental News Network, September 12, 1999)
    http://www.enn.com/enn-news-archive/1999/09/091299/marine_5507.asp

    Humans Altering Earth for the Worse (Environmental News Network, August 5, 1999)
    http://www.enn.com/enn-news-archive/1999/08/080599/deadzone_4798.asp

    Global Warming Serves Notice for Public Health (Environmental News Network, March 28, 2000)
    http://www.enn.com/enn-news-archive/2000/03/03282000/gwhealth_11241.asp

    EPA’s Climate Change Site
    http://www.epa.gov/climatechange/index.html

    Is Global Warming Harmful to Health? (Epstein, P.R. Scientific American, Aug. 2000)
    http://www.sciam.com/article.cfm?id=is-global-warming-harmful
    (Also available on author’s website at http://chge.med.harvard.edu/about/faculty/journals/sciam.pdf.)

  8. Melting of Arctic Ice Cap

    Bolles, E.B. 2000. In the (Un)Frozen North. New York Times, August 23, 2000. Wednesday, Science Desk.

    Easterbrook, G. 2000. Get The Easy Greenhouse Gases First. New York Times, August 29, 2000. Tuesday, Science Desk.

    Wilford, J.N. 2000. Ages-Old Icecap at North Pole is Now Liquid, Scientists Find. New York Times, August 19, 2000. Saturday, Science Desk.

    Wilford, J.N. 2000. Open Water at Pole is Not Surprising, Experts Say. New York Times, August 29, 2000. Tuesday, Science Desk.

    Campaign 2000: Environment; Protecting the Earth. New York Times, August 28, 2000. Monday, Editorial Desk.

  9. Melting of Antarctic Ice Cap

    Recent Changes to Antarctic Peninsula Ice Shelves: What Lessons Have Been Learned? (Natural Science)
    http://www.naturalscience.com/ns/articles/01-06/ns_clh.html

    Antarctic Ice Shelves Melting (Freedom Press)
    http://members.aol.com/blisswow/ice.html

    Is the Antarctic Ice Cap Melting?
    http://www.st-agnes.org/~dcrank/student/megan~2.html

  10. El Niño

    ENN Special Reports: El Niños (Environmental News Network)
    http://www.enn.com/specialreports/elnino/

    What is an El Niño? (NOAA)
    http://www.pmel.noaa.gov/tao/elnino/nino-home.html
    (excellent site with a 1 megabyte El Niño animation)

  11. Concern over biodiversity

    Biodiversity Under Siege from Titicaca to Timbuktu (Abley, M., Environmental News Network, July 22, 2000)
    http://www.enn.com/enn-news-archive/2000/07/07222000/biodiversity_14930.asp

  12. Ocean Farming Inc. Venture

    Testing the Waters (Schueller, G., New Scientist, Oct. 2, 1999)
    http://www.newscientist.com/article/mg16422064.800-testing-the-waters.html

    Fertilizing the Sea (Nadis, S. Scientific American, Apr. 1988)

    Fishing for Markets: Regulation and Ocean Farming (Markels, M., Jr., Regulation Vol. 18, No. 3, 1995)
    http://www.cato.org/pubs/regulation/reg18n3h.html

    Overview and Future Directions for the National Sea Grant Aquaculture Program (James McVey, National Sea Grant College Program)
    http://www.soest.hawaii.edu/SEAGRANT/ooc.html

  13. Effects of surface blooms

    Testing the Waters (Schueller, G., New Scientist, Oct. 2, 1999)
    http://newscientist.com/ns/19991002/testingthe.html

  14. Zooxanthellae, corals, and temperatures

    El Niño Causing Coral Bleaching in Galapagos, NOAA Announces. January 20, 1998 press release. National Oceanic and Atmospheric Administration
    http://www.publicaffairs.noaa.gov/pr98/jan98/noaa98-004.html

    Birkeland, C. (ed.) 1997. Life and Death of Coral Reefs. Chapman & Hall.

    Hickman, C.P. Jr., et al. 1996. Integrated Principles of Zoology. WCB/McGraw-Hill.

  15. Harmful algal blooms

    State of the Coastal Environment: Harmful Algal Blooms (NOAA)
    http://state-of-coast.noaa.gov/bulletins/html/hab_14/hab.html

    Harmful Algae Page (Woods Hole Oceanographic Institution)
    http://www.whoi.edu/redtide/

    Toxic Red Tides and Harmful Algal Blooms (Rev. Geophys. Vol. 33 Suppl., 1995)
    http://earth.agu.org/revgeophys/anders01/anders01.html

    Harmful Algal Blooms (Florida Fish and Wildlife Conservation Commission)
    http://research.myfwc.com/features/default.asp?id=1018

  16. Detrimental effects of diatoms

    Testing the Waters (Schueller, G. New Scientist, Oct. 2, 1999)
    http://www.newscientist.com/article/mg16422064.800-testing-the-waters.html

  17. IronEx III

    The iron hypothesis: Basic research meets environmental policy, Sallie W. Chisolm, Department of Civil and Environmental Engineering, and Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts
    http://www.agu.org/revgeophys/chisho00/chisho00.html

    Iron and its Effects on the Carbon Cycle in Oceans (compiled by Bernadette Pate Holt, Bell County Network for Educational Technology)
    http://www.co.bell.tx.us/bellnet/bellnetweb/web/ironand.htm

    Natural Iron Enrichment in Ocean Fronts (Ken Johnson, Francisco Chavez, Monterey Bay Aquarium Research Institute) http://www.mbari.org/MUSE/Participants/Chavez-Johnson.html
    (Please note: According to the EPA, IronEx III has been renamed Southern Ocean Fertilization Experiments, or SOFeX)

Editor’s Note: Readers interested in this case will also be interested in “The Geritol Solution” by Deborah E. Allen, which explores this same topic through problem-based learning. “The Geritol Solution” can be found in Thinking Toward Solutions: Problem-Based Learning Activities for General Biology, D.E. Allen and B.J. Duch, eds., Saunders Publishing Co., 1998.

Acknowledgements: This case was developed with support from The Pew Charitable Trusts and the National Science Foundation as part of the Case Studies in Science Workshop held at the State University of New York at Buffalo on June 12–16, 2000.

Date Posted: September 21, 2000.

Originally published at http://www.sciencecases.org/iron_fertilization/notes.asp

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