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“The Geritol Solution”: C Transformations in the Ocean

Student Directions

About 20 years ago an oceanographer named John Martin made an odd discovery in the eastern Pacific Ocean. The waters in this area are normally very blue because so few phytoplankton (microscopic floating algae) grow there. What had long puzzled Martin were the high concentrations of nutrients such as nitrogen and phosphorus in the water; usually when these nutrients are abundant, phytoplankton growth is high and water is green colored. Martin had the idea that iron, not nitrogen and phosphorus, limited the growth of phytoplankton in these waters. To test this idea, he added iron to a 10x10 km area (a kilometer - km - is about 0.6 miles). The waters quickly turned a soupy-green color and phytoplankton were clearly in abundance.

Martin proposed adding iron to parts of the Pacific Ocean as a partial solution to the rising concentration of CO2 globally. This was dubbed the "Geritol Solution", named after the well known iron supplement, Geritol (for "iron tired blood"). By spreading half a ton of iron across 100 square kilometers of the Pacific, the oceanographers had stimulated enough plant growth to take up about 350,000 kilograms of carbon dioxide from the seawater. If done on a large scale, iron fertilization of ocean water could absorb billions of tons of carbon dioxide from the air, which according to some rough estimates would be enough to slow the rate of global warming caused by excess CO2 and other greenhouse gases in the atmosphere.

As you can imagine, this proposal was - and still is - very controversial. The questions below will help you understand part of the controversy.

Read through the statements below so that you understand what Dr. Skeptic's concern is, and then analyze what she says. The questions will guide you in the analysis.

Imagined conversation between Dr. John Martin and Dr. Jean Skeptic:

Dr. Martin: "We should try the ‘Geritol solution' experiment on a much larger scale and see what happens to global atmospheric CO2 ."

Dr. Skeptic: "I don't agree at all. You have not shown that over the longer term this so-called ‘solution' will work!"

Dr. Martin: "Why not?"

Dr. Skeptic: "Well one of the main things that worries me is that the phytoplankton will eventually die and be decomposed. If this happens, the Geritol ‘solution' is no solution at all!"


1. In your own words, describe Dr. Skeptic's concern. Why is she worried that if decomposition takes place, the Geritol Solution will not work?











2. Make a drawing showing what happens to C in the atmosphere when iron is added to the ocean in the Pacific region. What form is C in the atmosphere and where does the C go? What is this process? Next, show the path that C takes during the process of decomposition that is of such concern to Dr. Skeptic and explain why this is a problem for supporters of the "Geritol Solution". Make sure your drawing includes the changes in C, what the processes? are, and why they take place (why the organisms ‘do' them). Note: there is carbon dioxide in water.











The SOIREE experiment stimulated Plankton Bloom in the Southern Ocean (1999). By addition of micro-nutrient iron by a consortium of scientists from a dozen countries.


4.CC_Geritol_Solution_Revised.doc362 KB