Development of Iron Fertilization Science


1. Iron Fertilization Is a Truly New Concept. The fundamental concept that iron controls the growth of phytoplankton in much of the world’s oceans was formally postulated with supporting data in the late 1980’s. During the 1990’s and into 2002, a series of experiments, ranging from bench-scale assays to large-scale fertilizations of 100-sqare kilometer patches of ocean from the North Pacific to Antarctica, have been conducted to test the “iron hypothesis” and the results of these experiments have confirmed the initial hypothesis.

2. John Martin’s Role – Dr. John H. Martin, Director of the Moss Landing Marine Laboratories, is credited with formulating the “iron hypothesis”, the concept that availability of iron controls primary production in much of the world’s oceans and may be one of the primary factors controlling world climate.

A brief history of Martin’s role in developing, testing and publicizing the role of iron may be found at
. Martin’s formulation of the idea included:
  • In the early 1970’s, Martin became expert in the study of trace metals in ocean waters, which include the micronutrient iron;
  • Because iron abundance reported in scientific literature appeared suspiciously random, Martin and his colleagues surmised that most seawater samples had been contaminated. Results from the “ultraclean” laboratories subsequently established showed that much ocean water did not have enough iron to support photosynthesis.
  • Martin and colleagues conducted a series of “bottle experiments” which showed that addition of iron caused rapid growth of phytoplankton. Using dust and carbon dioxide captured in Antarctic ice cores
    as the primary evidence, Martin postulated that changes in the amounts of iron in windblown dust from Asia could trigger Ice Ages.

In 1991, Martin attracted the attention of the world with his frank speculation that deliberate iron fertilization could control atmospheric carbon dioxide levels. His “Give me half a tankerload of iron, and I’ll give you an Ice Age” quip came at the time when awareness of global warming was emerging but very poorly understood.

Martin died in 1993, shortly before the first “perturbation” experiment designed to tested the iron hypothesis. This and subsequent experiments have confirmed the verity and importance of his idea.

3. A Series of Experiments Confirm the Iron Hypothesis – Since Martin’s death, a series of experiments have demonstrated that the iron hypothesis can predict the responses of phytoplankton under actual conditions. Several of the experiments have triggered large, spectacular blooms with addition of very small amounts of iron. Notable experiments include:

– 1993, IronEx I – This National Science Foundation funded experiment was the first to spread iron sulfate over a 64 square kilometer area due west of the Galapagos. Phytoplankton growth responded, but the experiment was cut short. This experiment, described in
, confirmed the accuracy of the iron hypothesis but not its significance.

-1995 IronEx II – This experiment successfully triggered a bloom with tenfold increases in phytoplankton concentrations, by applying iron in the same general area as the IronEx I experiment. This “biblical” bloom changed the color of the water from blue to green and provided the most vivid proof of the validity of the iron hypothesis.

-NSF Experiments Pause From 1995 to 2002 – Although the IronEx II results were widely considered very significant, no subsequent NSF cruises were undertaken for seven years. This delay, which chagrined oceanographers, illustrates how the expense and logistics of iron fertilization research strain limited budgets for oceanographic research.

– February 1999, Southern Ocean Seeded By Southern Ocean Iron Release Enrichment Experiment (SOIREE). This was the first of the perturbation experiments in the Southern Ocean. The consortium led by a New Zealand Oceanographic institute, essentially duplicated the IronEx II experiment in the Southern Ocean. SOIREE did manage to produce a bloom within their patch, but adverse weather conditions did not allow tracking of the patch.

-January-March 2002, the Southern Ocean Iron Fertilization Experiment (SOFeX) Conducts First Clearly Successful Iron Experiments in the Southern Ocean. This series, described at
was able to cultivate and track two patches in the Southern Ocean and disproved a theory which, if true, would diminish the potential significance of the “iron hypothesis”.