In October 1993, an interdisciplinary group of scientists
spread 445 kg of iron over a 64 km
patch of surface ocean in
the eastern equatorial Pacific. They monitored the patch for
9 days, comparing its biology and chemistry to the unfertilized
surrounding waters. They found that the phytoplankton (microscopic
plants which comprise the base of the food web in the oceans) were
three times more productive in the patch than outside it. In other
words, the cells were photosynthesizing---i.e., converting
CO
to organic carbon---at a significantly enhanced rate.
The group concluded that iron was the limiting factor in this
ecosystem, solving one of the more perplexing puzzles in biological
oceanography in recent years. This event marked not only the first
unenclosed ocean ecosystem experiment, but also the climax to a
complex and fascinating evolution of ideas in biological
oceanography. The climax was bittersweet, however, as John Martin,
the designer of the experiment and originator of the hypothesis,
died shortly before the expedition.
The story behind the iron enrichment experiment is interesting not only for the scientific results per se, but also because it reveals why straightforward answers to simple questions are difficult to come by in biological oceanography. More importantly, the results of this experiment, and the events that led up to it, contain important lessons for those working at the interface between science and public policy.