Ocean fertilization is a controversial idea, prompting protest from those who fear the unintended environmental impacts it may have.
"Most scientists would agree that we are nowhere near the point of recommending [iron fertilization of the oceans] as a geoengineering tool. But many think that larger and longer [iron fertilization] experiments should be performed to help us to decide which, if any, of the many geoengineering options at hand should be deployed," Buesseler wrote.
Phytoplankton, which includes microscopic marine plants and photosynthetic microbes, blooms naturally in the ocean. However, in seawater, there is only limited iron, an element these organisms need to grow, so by adding iron to seawater, it's possible to make a man-made bloom.
In this study, the researchers fertilized an eddy because it offered a largely self-contained system, or "a gigantic test tube," said lead researcher Victor Smetacek, with the Alfred Wegener Institute for Polar and Marine Research in Potsdam, Germany.
By mixing an iron fertilizer into the seawater, the researchers created the equivalent of a good-size spring bloom like those seen in the North Sea or off Georges Bank off the New England coast, which turned the water from blue to turquoise, Smetacek said.