The Iron Experiments
Richard Barber's Team Goes to the End of the Earth to See
if Dust Once Played a Role in Climate Change p.4
Hilting’s jobs included collecting
seawater samples in clusters of bottles called rosettes. Portions
of those samples were then distributed to the Melville’s entire
research team. The Duke technician also measured the primary
productivity of plants she collected to assess how much new
organic matter was produced via photosynthesis. To do those
measurements, she incubated the plants in a ship lab using
a radioactive tracer to measure carbon uptake.
Barber himself did those primary
productivity measurements for samples collected aboard the
Revelle, leaving graduate student Lance with what
he says was the more difficult jobs of measuring photosynthetic
performance of phytoplankton and serving as senior author
of the cruise paper assessing primary productivity. Lance
will ultimately write her dissertation on iron’s effects on
phytoplankton growth in a variety of different habitats. Barber’s
job of simply measuring primary productivity as opposed to
interpreting what it all means was comparatively “less intellectually
demanding,” he says.
“It’s a division of labor between
graduate students who are the hotshots and tired old faculty,”
he quips self-deprecatingly, noting that Hiscock was in turn
senior author of the cruise paper on quantum yield.
Stuebe, a Duke senior at the time
of the cruise, used his time aboard the Revelle to
process computerized mapping data and was able to track how
the iron patches were spreading within both patches by monitoring
the sulfur hexafluoride tracer. “He would take water samples
about every 30 minutes as the ship went back and forth,” Barber
recalls. “It was something he could intellectually handle
because he’s so good at math.” Steube is now a graduate student
at Woods Hole Oceanographic Institution in Massachusetts.
Through such shipboard work experiences,
Barber’s students “become enormously impressed by how hard
it is to describe a natural ocean system even for a few days,”
he says. “Most of the people just worked their hearts out
under very unfavorable conditions, day after day.”
According to a summary news release
from the Moss Landing Marine Laboratories, the SOFeX cruise
“reveals that iron supply to the Southern Ocean may have controlled
Earth’s climate during past ice ages.”
In the iron-seeded patches, both
in the high and low silicon zones, “blooms” of marine plants
formed that covered thousands of square kilometers—large enough
to be visible in satellite images. And each of these blooms
“consumed over 30,000 tons of carbon dioxide,” the release
estimates. Moreover, even in the siliconpoor patch, non-diatom
marine plants managed to “consume vast amounts of carbon dioxide.
This finding has doubled the area of the Southern Ocean that
scientists believe could be important for carbon cycling.”
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