The Iron Solution

John Martin of the Moss Landing Marine Laboratory proposed (Nature 345, issue 3/4 in 1990) that excess carbon dioxide could be removed from the atmosphere by using iron fertilizer to stimulate the growth of algae in the polar oceans. The idea comes from the fact that iron is the limiting nutrient for biological growth in the polar oceans, which have abundant levels of phosphate, nitrate and silicate (see Robin S. Keir, Nature 349, 198 [1991]). This was shown (Nature 348, 188 [1990]) to be hugely expensive, potentially dangerous, and minimally effective. More recent discussion points out advantages and disadvantages.

A news release in October 1996 by the National Science Foundation reported preliminary results with an experiment off the Galapagos Islands in which phytoplankton were fertilized with about 450 kg of iron. The result was that the growth of phytoplankton stimulated by this fertilization consumed an additional 2.3 million kg of carbon dioxide at the atmosphere/ocean interface.

Below are Nimbus-7 scanner data for phytoplankton concentration from November 1978 to June 1986 showing the abundance of biological activity in polar oceans.