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SUMMARY:Southern Ocean iron fertilisation by baleen whales and Antarctic k
 rill - Dr Steve Nicol (Australian Antarctic Division)
DTSTART:20101119T110000Z
DTEND:20101119T120000Z
UID:TALK27963@talks.cam.ac.uk
CONTACT:Sophie Fielding
DESCRIPTION:Iron is the limiting micronutrient in the Southern Ocean and e
 xperiments have demonstrated that addition of soluble iron to surface wate
 rs results in phytoplankton blooms\, particularly by large diatoms. Antarc
 tic krill (Euphausia superba) eat diatoms and recycle iron in surface wate
 rs when feeding. Baleen whales eat krill and historically defecation by ba
 leen whales could have been a major mechanism for recycling iron\, if whal
 e faeces contain significant quantities of iron. We analysed the iron cont
 ent in 27 samples of faeces from 4 species of baleen whale. Faecal iron co
 ntent (145.9 +/- 133.7 mg kg-1) is approximately ten million times that of
  Antarctic seawater\, suggesting that it could act as a fertiliser. Furthe
 r\, we analysed the iron content of seven krill species and of muscle tiss
 ue of two species of baleen whales\; all samples had high iron levels. Usi
 ng 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 ac
 t as a long term reservoir of iron in Antarctic surface waters\, by storin
 g the iron in their body tissue. Pre-exploitation populations of whales an
 d krill must have stored larger quantities of iron and would have also rec
 ycled more iron in surface waters\, enhancing overall ocean productivity t
 hrough a positive feedback loop. Thus\, allowing the great whales to recov
 er might actually increase Southern Ocean productivity through enhancing i
 ron levels in the surface layer. This enhanced productivity would increase
  the ability of the Southern ocean to absorb atmospheric CO2.
LOCATION:British Antarctic Survey\, Room 330B
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