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Phenomena, Comment and Notes

Experiments at sea show we can cause phytoplankton to bloom in areas where it otherwise would not. This could remove carbon dioxide from the atmosphere and slow global warming

A light industrial area on the outskirts of Salinas, California, is probably the last place that you would think to look for an oceanographic institute. Yet, that is exactly where I found the Moss Landing Marine Laboratories, the birthplace of one of the decade's most startling scientific experiments.

The experiment, carried out in May and June of 1995, in an open stretch of the Pacific 800 miles west of the Galápagos Islands, involved an attempt to stimulate the growth of plankton by dumping iron into the ocean. During the two weeks of the experiment, the additional plankton that resulted from the fertilization pulled about 2,500 tons of carbon from the water, carbon that eventually would be in large part replenished from the atmosphere.

It was 1987 when oceanographer John Martin at Moss Landing first conceived what has come to be called the "iron hypothesis." Martin, who died in 1993, was a rather extraordinary individual. Working from a wheelchair since a bout with polio, he nonetheless managed on occasion to ship out with his research teams aboard the cramped, overcrowded vessels that are the oceanographer's primary labs. He noted that there are huge areas of ocean (mainly in the waters surrounding Antarctica and in the equatorial Pacific) that have large amounts of nutrients in the form of nitrogen compounds, but very few plankton. These regions also seem to have very low concentrations of iron-on the order of two parts per trillion. Just as lack of a single vitamin or trace mineral can stunt the growth of humans, Martin argued, the dearth of plankton in these otherwise nutrient-rich waters was because of the scarcity of iron.

What interested first Martin and now his successor, Kenneth Coale, are the ocean's phytoplankton — minute floating plants that, like all plants, pull carbon dioxide from their environment and convert it into molecules that they need to live. Think of them as the oceanic equivalent of prairie grass. Stimulating a plankton bloom is the equivalent of fertilizing a prairie. The plants remove carbon dioxide from the atmosphere (directly or indirectly) and store the carbon in their tissues.

Finding ways to remove carbon dioxide from the atmosphere has become a serious business. The surface of the earth is heated by the sun. So-called greenhouse gases — carbon dioxide, methane and water vapor, among others — prevent some of that heat from radiating back out into space. Even without any human activity, the world is about 60 degrees Fahrenheit warmer than it would be without this "greenhouse effect." By the burning of coal and oil — not to mention the burning of tropical rain forests-human beings now add measurable quantities of carbon dioxide to the atmosphere and may be raising the world's temperature.

But draw enough carbon dioxide out of the atmosphere, scientists predict, and that temperature will drop. "Give me a half a tanker of iron," Martin once said, "and I'll give you the next ice age." It wasn't all bluster. Scientists now estimate that iron fertilization could, in principle, remove as much as 20 percent of the human-generated carbon dioxide from the atmosphere at a cost less than alternatives such as large-scale tree planting.

When the first field trial of the idea was conducted in the fall of 1993, shortly following Martin's death, however, things stopped looking so simple. This was what engineers call a "proof of concept" experiment. "The main purpose," says Coale, "was to see whether you could lay down a patch of iron-rich water in the ocean." The iron, in the form of iron sulfate, was fed through two pipes in back of the ship's propellers and dispersed into the ocean. "Being in an agricultural area like the Salinas Valley was a big help," Coale says. "All the equipment for moving around large amounts of fertilizer is available right here."

In a narrow sense, the first experiment was a success. A patch of iron-rich water formed. The concentration of phytoplankton in the patch, however, was only twice that of the surrounding water. In the minds of many, this constituted a serious failure of the whole idea.

There was at least one good reason for this disappointing performance. On the fifth day after the fertilization, less salty and therefore lighter water moved in, burying the patch under a hundred feet of water, away from the light.

I was at the meeting in San Francisco when these results were announced in 1994, and I was really taken aback by the reaction to them. As someone who has, during a checkered career, been involved in a couple of large-scale engineering projects, I wasn't surprised at this type of "failure." In projects like this, the first trial always fails-think of the first American attempts at spaceflight. What surprised me was the reaction of the environmental scientists present. It was almost as if there was a collective sigh of relief, as if the prospect that humanity might find an easy way out of the greenhouse problem was just too much for them to bear. Having heard many of those same scientists advocate the large-scale planting of trees to pull carbon out of the air, I couldn't help wondering why they were so dismayed at the notion of growing phytoplankton instead.

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