Adding iron to the diet of marine plant life has been shown in shipboard
experiments to boost the amount of carbon-absorbing phytoplankton in
certain parts of the worlds oceans. A new study promises to give
scientists their first global picture of the extent of these unique
iron-limited ocean regions, an important step in understanding how the
oceans biology controls the flow of carbon between the atmosphere and
The new study by researchers at NASA’s Goddard Space Flight Center and
the Department of Energys Oak Ridge National Laboratory was presented
at the American Geophysical Unions annual meeting in San Francisco on
Friday, Dec. 15, 2000.
Oceanic phytoplankton remove nearly as much carbon from the atmosphere
each year as all land-based plants. Identifying the location and size
of nutrient-limited areas in the open ocean has challenged
oceanographers for nearly a century.
The study pinpointed iron-limited regions by seeing which
phytoplankton-rich areas of the worlds oceans were also areas that
received iron from wind-blown dust. In this map, areas with high levels
of chlorophyll from phytoplankton and high levels of dust deposition
(high correlation coefficients) are indicated in dark brown. Dust deposition
was calculated by a 3-year modelled climatology for the years 19961998.
The chlorophyll measurements are from 1998 observations from the
SeaWiFS (Sea-viewing Wide Field-of-view Sensor) instrument on the
Global, satellite-based analyses such as this gives us insight into
where iron deposition may be limiting ocean biological activity, says
lead author David Erickson of Oak Ridge National Laboratorys Computer
Science and Mathematics Division. With this information we will be
able to infer how the ocean productivity/iron deposition relationship
might shift in response to climate change.