Recent experiments in the Southern Ocean offer the promise of controll

Recent experiments in the Southern Ocean offer the promise of controlling the threat of global warming by creating organic "sponges" for carbon dioxide, which is widely considered the main culprit for rising global temperatures. Scientists were able to grow a lush strip of phytoplankton 150 kilometers long by fertilizing a patch of the ocean with hundreds of kilograms of an iron compound. Phytoplankton presently accounts for over half of the photosynthesis on Earth, the process by which carbon dioxide is absorbed and converted into oxygen. A major limiting factor in the production of phytoplankton is lack of iron, but by fertilizing oceans with iron compounds scientists hope to be able to reduce carbon dioxide levels and reverse the greenhouse effect.

Which of the following, if true, casts the most serious doubt upon the advisability of using the fertilization method described above to control carbon dioxide levels?


(A) In some oceans, the growth of phytoplankton is also limited by how much nitrogen, phosphorus, and silicon are available.

(B) The cost of fertilizing the oceans with sufficient quantities of iron to reverse the greenhouse effect is likely to be very high.

(C) Iron naturally reaches the seas in the form of wind-blown mineral dust, which becomes more or less abundant as conditions on land change.

(D) Fertilization efforts will do nothing to curb the production of more carbon dioxide emissions.

(E) The oceans are a complex system, and the long-term consequences of ocean fertilization may be the opposite of what is predicted.