Daily rations and growth of larval krill Euphausia
superba in the Eastern Bellingshausen Sea during austral
autumn
E.A. Pakhomov1,3,
A. Atkinson2, B. Meyer3, B. Oettl3 and U. Bathmann3
1. Department of Zoology, University of Fort
Hare, Private Bag X1314, Alice 5700, South Africa.
E-mail: epakhomov@ufh.ac.za
2. British Antarctic
Survey, Natural Environment Research Council, High Cross, Madingley Road,
Cambridge CB3 0ET, United Kingdom
3. Alfred-Wegener-Institute for
Polar and Marine Research, Am Handelshafen 12,
D-27515 Bremerhaven, Germany
As the German
contribution to the Southern Ocean Global Ocean Ecosystems Dynamics (SO
GLOBEC), RV Polarstern visited the Eastern Bellingshausen Sea between 18 April and 1
May 2001 on
the ANTARKTIS XVIII/5b expedition. This paper examines in situ deal feeding
cycles, ingestion rates, daily rations and growth of larval krill Euphausia
superba, with additional measurements of feeding activity of selected
zooplankton species. Larval krill were
exceptionally numerous, especially over the shelf, mean 8872 larvae.m-2,
maximum 30084 larvae.m-2. Krill larvae over the shelf had an
advanced developmental stage composition when compared to larval assemblage at
continental slope stations. This probably resulted from enhanced food
availability on shelf stations. Despite late autumn,
feeding activity of selected zooplankton species, including larval krill but
with exception of Calanoides acutus, was similar to summer levels. The
intermoult period of larval krill ranged from 12 to 15 days, with daily
growth rates reaching 0.9-1.1% of body length, 3.3-4.5% of body wet mass and
2.2-2.9% of body carbon. Daily ingestion rates during April and May 2001 in the
Eastern
Bellingshausen Sea were 8.5-17.6 μgC.ind.-1d-1
for calyptopis 3 to furcilia 2 and 35.1-57.4 μgC.ind.-1d-1
for furcilia 3 to 5, and were positively correlated with ambient chlorophyll-a
concentrations. Daily rations of larval krill showed the same tendency, ranging
from 21.5 to 44.5% body C d-1 (calyptopis 3 to furcilia 2) and from
17.8 to 29.2% of body C d-1. Comparison of daily rations obtained at
the open water and sea ice stations, supports the notion that larval krill at
low pelagic food supply under the sea ice have to exploit ice biota to sustain
their metabolic demands.
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