region is characterized by a huge front in silicate, another nutrient
needed by some species of phytoplankton. The lines on this slide
represent distance, latitude, and low concentrations of silicate
north of the convergence zone, and high concentrations south. It's
right at this interface that we find this bloom and fluorescence
and this decrease in nitrate.
But we believe that there are fundamental differences in phytoplankton
response to added iron, both north of the fronts and south of the
curves represent enrichment experiments performed in bottles with
added, iron and measured chlorophyll concentrations. Also represented
are the phytoplankton responses south of the polar front zone in
high silicate area, and the response north of the front where there
is low silicate. So the silicate concentration is going to have
a dramatic effect on export from these two regions.
scientific questions remain. Does iron enrichment result in the
export of carbon? We think yes, in the Equatorial Pacific, and I
think the jury is still out with respect to the Southern Ocean.
What were the temporal and spatial scales of transport, remineralization
and sequestration of carbon in the deep ocean? We don't know the
answer. What were the biogeochemical consequences of iron fertilization?
In every case in the Equatorial Pacific, we see Nitzchia species
coming up as the dominant diatom, which can form toxic blooms under
certain environmental conditions.
Other problems mentioned today are the production of nitrous oxide
or methane in the deep waters, and the potential for denitrification.
What are the proxies for carbon sequestration? Finally, I'd like
to briefly discuss some of the nonscientific questions.
slide is from 1998 and there is already a decrease in the human
growth rate in the developing countries but a dramatic increase
in developing country populations. This increase will result in
even more dramatic concentrations of atmospheric CO2.