Researchers publish results of an iron fertilization experiment

The results, which were published in the scientific journal Nature, provide a valuable contribution to a better understanding of the global carbon cycle

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. These results, which were thoroughly analyzed before 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.

Read more: http://www.eurekalert.org/pub_releases/2012-07/haog-rpr071712.php

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