The second iron fertilisation experiment in the Atlantic sector of the Southern Ocean (EIFEX) was carried out for 37 days during the austral autumn of 2004 (January-March) in a mesoscale eddy, whose centre was fertilised twice (days 1 and 15). Phytoplankton pigments determined by HPLC and microscopic cell counts were monitored in the water column, in sediment traps and from surface sediments. Chlorophyll a standing stocks increased 3 fold until day 26, but remarkably decreased thereafter. The main beneficiaries of the iron fertilisation were again diatoms, especially Chaetoceros dichaeta, C. atlanticus, Pseudo-nitzschia lineola and Fragilariopsis kerguelensis. Towards the end of the experiment, the diatom marker fucoxanthin and chlorophyll a could be followed down the water column to 4000 m. A low ratio of phaeopigments to chl a indicate the export of fresh material most likely originating from the iron fertilised patch. This is corroborated by a similar diatom composition at the surface and at the bottom of the water column. Results from sediment trap and surface sediment data will be presented and the implication of export from iron-induced phytoplankton blooms will be discussed.
AWI Organizations > Geosciences > Marine Geochemistry
Helmholtz Research Programs > MARCOPOLI (2004-2008) > POL2-Southern Ocean climate and ecosystem