This pretty well puts the iron question to bed. We are assured that
if we wish to reduce CO2 content in the ocean and place it back into
the geological storehouse, it is enough to provide ample iron. Now
if we could find a clever way to work with mother Earth to do this we
may have an important technology.
We will not see much more in terms of experimentation until we
discover a good economic reason to do this.
In the event it is good to know.
Researchers publish results of an
iron fertilization experiment
by Staff Writers
Munich, Germany (SPX) Jul 20, 2012
Iron plays an
important role in the climate system. It is involved in many
biochemical processes such as photosynthesis and is hence an
essential element for biological production in the oceans and,
therefore, for CO2 absorption from the atmosphere.
An international
research team has published the results of an ocean iron
fertilization experiment (EIFEX) carried out in 2004 in the current
issue of the scientific journal Nature. Unlike the LOHAFEX experiment
carried out in 2009, EIFEX has shown that a substantial proportion of
carbon from the induced algal bloom sank to the deep sea floor.ore
being published now, provide a valuable contribution to our better
understanding of the global carbon cycle.
An
international team on board the research vessel Polarstern
fertilized in spring 2004 (i.e. at the end of the summer season in
the southern hemisphere) a part of the closed core of a stable marine
eddy in the Southern Ocean with dissolved iron, which stimulated the
growth of unicellular algae (phytoplankton). The team followed the
development of the phytoplankton bloom for five weeks from its start
to its decline phase.
The maximum biomass
attained by the bloom was with a peak chlorophyll stock of 286
Milligram per square metre higher than that of blooms stimulated by
the previous 12 iron fertilization experiments.
According to Prof. Dr.
Victor Smetacek and Dr. Christine Klaas from the Alfred Wegener
Institute for Polar and Marine Research in the Helmholtz Association,
this was all the more remarkable because the EIFEX bloom developed in
a 100 metre deep mixed layer which is much deeper than hitherto
believed to be the lower limit for bloom development.
The bloom was
dominated by diatoms, a group of algae that require dissolved silicon
to make their shells and are known to form large, slimy aggregates
with high sinking rates at the end of their blooms.
"We were able to
prove that over 50 per cent of the plankton bloom sank below 1000
metre depth indicating that their carbon content can be stored in the
deep ocean and in the underlying seafloor sediments for time scales
of well over a century", says Smetacek.
These results contrast
with those of the LOHAFEX experiment carried out in 2009 where diatom
growth was limited by different nutrient conditions, especially the
absence of dissolved silicon in the chosen eddy. Instead, the
plankton bloom consisted of other types of algae which, however, have
no protective shell and were eaten more easily by zooplankton.
"This shows how
differently communities of organisms can react to the addition of
iron in the ocean", says Dr. Christine Klaas. "We expect
similarly detailed insights on the transportation of carbon between
atmosphere, ocean and sea bottom from the further scientific analysis
of the LOHAFEX data", adds Prof. Dr. Wolf-Gladrow, Head of
Biosciences at the Alfred Wegener Institute, who is also involved in
the Nature study.
\
Iron plays an
important role in the climate system. It is involved in many
biochemical processes such as photosynthesis and is hence an
essential element for biological production in the oceans and,
therefore, for CO2 absorption from the atmosphere.
During past ice ages
the air was cooler and drier than it is today and more
iron-containing dust was transported from the continents to the ocean
by the wind. The iron supply to marine phytoplankton was hence higher
during the ice ages. This natural process is simulated in iron
fertilisation experiments under controlled conditions.
"Such controlled
iron fertilization experiments in the ocean enable us to test
hypotheses and quantify processes that cannot be studied in
laboratory experiments. The results improve our understanding of
processes in the ocean relevant to climate change", says
Smetacek.
"The
controversy surrounding iron fertilization experiments has led to a
thorough evaluation of our results before publication", comments
the marinescientist as an explanation for the long delay
between the experiment to the current publication in Nature.
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