FeEx site was about 5 south, 90 degrees west, and is in a region
characterized by fast currents on the order of 2 knots. These high
flow ocean areas poses a particular challenge to biological and
chemical oceanographers trying to do an open ocean enrichment experiment
The first challenge was just trying to track where this patch
goes. We deployed a buoy that drifted along with the iron-enriched
water and reported the position back to the ship every few minutes.
A large shower curtain-like device called a drogue anchored this
buoy in the water column.
buoy then became the reference point around which the iron enrichment
experiment was conducted. The other challenge was to find a way
to add iron to the surface waters. We did that by filling large
tanks, adding iron sulfate. In addition, a tracer
of sulfuric hexafluoride was added to the tanks that enabled us
to detect where iron was applied. We then injected this solution
into the surface water at the stern of the ship. So the ship's propeller
actually functioned like a blender and the ship acted like a tractor
as the boat steamed out across the Equatorial Pacific, laying an
enriched patch of iron.
give you an idea of the scale of this experiment, here is a West
Coast example. The size of the patch would represent a significant
portion of Monterey Bay, which is a 100 square kilometers.
a look at this slide which depicts the phytoplankton's ability to
harness life's energy, and imagine that this red color represents
"happy" phytoplankton and these blue colors represent
As one steams across the patch, one can essentially measure the
happiness of the phytoplankton. We find, in fact, where iron was
enriched, the photosynthetic ability of the phytoplankton increased
to their maximum values within a very short time. Some of the first
indications that this experiment was working were achieved after
about two hours.