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SUMMARY:Characterisation of zooplankton vertical migration in two high Arc
 tic fjords using moored ADCPs - Mags Wallace (University of St Andrews)
DTSTART:20081202T110000Z
DTEND:20081202T120000Z
UID:TALK14903@talks.cam.ac.uk
CONTACT:Robert Bingham
DESCRIPTION:Zooplankton undertake vertical migration to feed near the surf
 ace and excrete in deeper water\, which contributes significantly to CO2 d
 rawdown. The classic behaviour is diel vertical migration (DVM)\, such tha
 t the animals move upward to feed during the hours of darkness and downwar
 d during daylight to escape predation. This synchronised movement of anima
 ls is driven by the light/dark cycle characteristic of spring and autumn a
 t high latitudes. Such behaviour is thus generally believed to cease durin
 g the periods of midnight sun and polar night\, and is also expected to de
 crease in the presence of sea ice due to light attenuation. However\, the 
 absence of a synchronised migration pattern does not necessarily presume t
 otal absence of animal migration. Here\, we present temporally coincident 
 data from acoustic Doppler current profilers (ADCP) moored in two Svalbard
  fjords.  This allows a direct comparison of zooplankton vertical migratio
 n in an ice-free and a seasonally ice-covered fjord over almost two years 
 (2006-08)\, making this the first study to quantify the annual variation i
 n migratory behaviour in the Arctic environment and its impact on carbon f
 lux. DVM is clearly observed at both sites during autumn and spring\, even
  in the presence of low light levels and significant sea ice cover. The la
 rgest contrasts between the two sites are observed during the midnight sun
 \, where weak synchronised vertical motions occur over much of the summer 
 at the ice-free site\, whereas the ice-covered station is characterised by
  asynchronous movement. Calculations of carbon flux suggest that DVM leads
  to reduced CO2 drawdown compared with unsynchronised vertical migration\,
  so future reduction in Arctic sea ice cover may lead to an increase in DV
 M and a decrease in CO2 flux. 
LOCATION:British Antarctic Survey\, Room 307
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