In 1993, shortly after Martin’s death, his colleagues at Moss Landing Marine Laboratories tested the hypothesis by increasing the concentration of iron over 64 square kilometers of the Pacific Ocean. They then observed the area for 10 days and saw the amount of plant biomass double. “All biological indicators confirmed an increased rate of phytoplankton production in response to the addition of iron,” they wrote in a paper detailing the experiment. More than a dozen other ocean fertilization experiments have been conducted since then, but even though they do appear to cause a bloom of plankton, it’s still not clear whether the approach could actually help combat climate change.
In 2009, researchers from the Department of Energy’s Lawrence Berkeley National Laboratory tracked the impact of a major ocean fertilization experiment in the Southern Ocean between New Zealand and Antarctica by measuring carbon particles 800 meters below the surface of the water in the area for a year — and their findings were less than encouraging. “Just adding iron to the ocean hasn’t been demonstrated as a good plan for storing atmospheric carbon,” said researcher Jim Bishop. “What counts is the carbon that reaches the deep sea, and a lot of the carbon tied up in plankton blooms appears not to sink very fast or very far.” While researchers are still trying to figure out why that is, there are a number of theories, including ones centered on the feeding habits of creatures that live off phytoplankton and the presence of iron-binding organic compounds in ocean water.
