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.



FINAL VERSION READY (hard copy + electronic version)