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SUMMARY:Southern Ocean phytoplankton: mapping iron stressed communities fr
 om space and strong responses to volcanic ash supply - Dr. Tom Browning\, 
 Department of Earth Sciences\, University of Oxford
DTSTART:20140716T130000Z
DTEND:20140716T140000Z
UID:TALK53247@talks.cam.ac.uk
CONTACT:Dr Alexander Brearley
DESCRIPTION:Phytoplankton emit fluorescent red light that can be detected 
 by sensors on earth-orbiting satellites. This fluorescence signal has the 
 potential to reveal information about the physiological status of phytopla
 nkton on a global scale. Realisation of this potential is however limited 
 because the controls governing fluorescence signatures are not well constr
 ained. In order to better understand these controls we conducted a suite o
 f measurements and experiments on cruises over a period of 4 months in the
  South Atlantic and Southern Ocean (via the UK-GEOTRACES and UK-DIMES proj
 ects). We found physiological changes in phytoplankton over broad oceanogr
 aphic regions that mean a dynamic correction needs to be added to existing
  methods attempting to deconvolve satellite-retrieved fluorescence. We hav
 e developed and applied such a correction\, revealing fluorescence signatu
 res that correlate well with anticipated\, and experimentally confirmed\, 
 regions of iron stress.\n\nIn austral summer\, phytoplankton in the ‘hig
 h-nitrate low-chlorophyll’ (HNLC) regions of the Southern Ocean are wide
 ly assumed to be limited by iron only. I will present evidence from a suit
 e of iron and volcanic ash enrichment experiments that suggest (i) phytopl
 ankton in these waters respond strongly to supply of volcanic ash\, and (i
 i) manganese could potentially be limiting phytoplankton growth in the mos
 t oligotrophic areas of the Southern Ocean. 
LOCATION:British Antarctic Survey\, Room 330B
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