Krill as a central node for iron cycling in the Southern Ocean

In order to establish the potential role of Antarctic krill ( Euphausia superba ) in the recycling of bioactive elements, we have quantified the release of iron, phosphate, and ammonia by these organisms along the Antarctic Peninsula sector of the Southern Ocean. The experimental results suggested that the presence of krill has a significant impact on ambient iron concentrations, as large amounts of this trace element were released by the krill (22–689 nmol Fe g Dry Weight −1 h −1 , equivalent to 0.2 to 4.3 nmol Fe L −1 d −1 ). Half of this iron release occurred within the first hour of the experiment, and differences in iron and phosphate release rates (3.1 to 14.0 μ mol PO 4 3− g DW −1 h −1 ) seemed to reflect differences in food availability. These results identify krill as a major node in iron cycling in the Southern Ocean, potentially influencing iron residence time in the upper water column of this region.