Jan van Franeker, Bram Feij, André Meijboom

IMARES
Wageningen
The importance of sea ice -
the predators
Jan van Franeker, Bram Feij, André Meijboom, Michiel van Dorssen & Hauke Flores
Postbus 167
1790 AD Den Burg (Texel)
The Netherlands
+31 222 369 724
Jan.vanfraneker@wur.nl
IMARES is a partner of the Alfred Wegener Institute (AWI)
in the Antarctic ‘Lazarev Sea Krill Study’ (LAKRIS). Our
contribution focuses on the biology in the upper water
layer in the seasonal sea ice zone. Birds, seals and
whales indicate that the sea ice ‘fuels’ the Antarctic
foodweb. In a ‘top down’ approach we specify the
food requirements of top predators and the
availability of prey under the sea ice. Understanding
the role of sea ice in sustaining the Antarctic krill stocks
and associated foodweb is vital to the assessment of
ecological impacts of climate change.
Density estimates of birds, seals and whales
are made by surveys from both ship and
helicopter. Densities can be translated to
daily food requirements of the combined
community of top predators. Preliminary
data shown here are from ship observations
2004, 2006 and 2007-08.
LAKRIS
Food from the seasonal sea ice
Throughout the year the seasonal sea ice zone
of the Lazarev Sea south of 55°S meets food
demands from birds and mammals that are
higher than those in the permanently open
water further north.
food requirement kg/km2/day
Food requirements of birds and mammals in the sea ice zone and open water
seasonal sea ice zone
(south of 55°S)
open ocean
(35-55°S)
14
12
10
8
6
4
2
0
AUTUMN
WINTER
2004 ANT-21-4
2006 ANT-23-6
SUMMER
2007-08
ANT-24-2
Seasonal changes in the food requirements of predators in the LAKRIS study area
327
25
10
5
AUTUMN
WINTER
SUMMER
2004 - ANT-21-4
2006 - ANT-23-6
2007-08 - ANT-24-2
-60
-60
-60
kg food
-61
-61
-61
per km2
per day
-62
-62
-62
-63
-63
-63
-64
-64
-64
-65
-65
-65
-66
-66
-66
-67
-67
-67
-68
-68
-68
-69
-69
-69
-70
-70
-70
-71
-71
-71
open water
sea ice
-9
Area
average
-6
-3
0
3
6
-9
2.5 kg km-2 day-1
Netherlands AntArctic Programme
-6
-3
0
4.8 kg km-2 day-1
3
6
LAKRIS has shown that
even in midwinter top
predators are attracted
deep into the heavy pack
ice.
Recently formed
young ice in autumn and
winter appears less
attractive. However, after
winter the melting of the
older ice apparently
releases such abundant
food that migrator y
animals move in from
1000’s of km’s away.
Animal populations of a
wide area depend on the
continued existence of the
Antarctic seasonal sea ice.
-9
-6
-3
0
3
14.6 kg km-2 day-1
LNV
6
9