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Iron is the limiting micronutrient in the Southern Ocean and experiments have demonstrated that addition of soluble iron to surface waters results in phytoplankton blooms, particularly by large diatoms. Antarctic krill (Euphausia superba) eat diatoms and recycle iron in surface waters when feeding. Baleen whales eat krill, and, historically, defecation by baleen whales could have been a major mechanism for recycling iron, if whale faeces contain significant quantities of iron. We analysed the iron content in 27 samples of faeces from four species of baleen whale. Faecal iron content (145.9 ± 133.7 mg kg)1) is approximately ten million times that of Antarctic seawater, suggesting that it could act as a fertilizer. Furthermore, we analysed the iron content of seven krill species and of muscle tissue of two species of baleen whales; all samples had high iron levels. Using these figures, together with recent estimates of the range and biomass of krill, we calculate that the Antarctic krill population contains 24% of the total iron in the surface waters in its range. Thus, krill can act as a long-term reservoir of iron in Antarctic surface waters, by storing the iron in their body tissue. Pre-exploitation populations of whales and krill must have stored larger quantities of iron and would have also recycled more iron in surface waters, enhancing overall ocean productivity through a positive feedback loop. Thus, allowing the great whales to recover might actually increase Southern Ocean productivity through enhancing iron levels in the surface layer.

Item Type:	Refereed Article
Keywords:	Baleen whales, iron fertilization, krill, Southern Ocean
Research Division:	Earth Sciences
Research Group:	Oceanography
Research Field:	Biological oceanography
Objective Division:	Environmental Management
Objective Group:	Coastal and estuarine systems and management
Objective Field:	Assessment and management of coastal and estuarine ecosystems
UTAS Author:	Nicol, S (Dr Stephen Nicol)
UTAS Author:	Bowie, AR (Professor Andrew Bowie)
UTAS Author:	Lannuzel, D (Associate Professor Delphine Lannuzel)
UTAS Author:	Meiners, K (Dr Klaus Meiners)
UTAS Author:	van der Merwe, P (Dr Pier van der Merwe)
ID Code:	67556
Year Published:	2010
Web of Science® Times Cited:	112
Deposited By:	IMAS Research and Education Centre
Deposited On:	2011-03-04
Last Modified:	2011-10-06
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