POLSKIE ARCHIWUM HYDROBIOLOGII (Pol. Arch. Hydrobiol.) 47 34* 579-584 2000 (Loot ) Fabienne Nyssenl'3*, Thomas Brey2, Gilles Lepoint, Jean-Marie Bouquegneaut, ClaudeDe Broyer3, Patiick Daubyl'3 Use of stable isotopes to delineate amphipod trophic status in Antarctic food webs rLaboratory of Oceanology, University of Lidge, Sart Tilman 86, 8-4000 Lidge, Belgium 2Alfred-Wegener-Institut fiir Polar- undMeeresforschung, Columbusstrasse, D-27568, Bremerhaven, Germany 3Royal Belgian Institute ofNaturalSciences (RBINS), 29 rueVautier, B-1000 Brussels, Belgium * e-mail: fabienne.nyssen@ulg.ac.be Abstract Within the Southern Ocean, amphipods have achieved a conspicuous ecological radiationwhich gave rise to the development of numerous feedingstrategies. The aim of this study is to apply the carbon and nitrogen stable isotope ratio methodology to delineate the trophic relationships involving benthic amphipods in the eastern Weddell Sea food webs. The interest of the isotope technique relies upon the direct relationship between the carbon 1'3C/t'C1 and nitrogen lt5NltN; stable isotope ratios of the animal tissues and its diet. Our results demonstrate the efficiency of the isotope ratio method to distinguish species displaying different feeding strategies. The large range (from 18 to -l9.5yoo for carbon and from 5.8 to l2.9yoo for nitrogen) of isotopic ratios atteststhe wide spectrum of amphipod nutrition patterns. Key words: Amphipoda, trophic types, carbon, nitrogen, stable isotopes,Antarctic 1" Introduction In the Weddell Se4 as in many areas of the Southern Ocean coastal and shelf ecosystems, the peracarid crustaceans, and the Amphipoda in particular, count among the most important components of the zoobenthos (Klages l99l; De Broyel Jaid2ewski 1996; De Broyer et al. 1999). By proviriing important food resources to many invertebrate and vertebrate organisms (McClintock 1994; Cherel, Kooyman 1998; Olaso et aL.2000),amphipod crustaceans appear to play an important role within the high Antarctic benthic system (Jarre-Teichmann 1997). Consideringthe potential importanceof amphipodsand the evident lack of knowledge about their * The issue, edited by: Krzysztof JaZdZewski (l-dd2, Poland),Adam Baldinger (Cambridge,MA, USA), Charles Oliver Coleman (Berlin, Germany), Claude De Broyer (Brussels, Belgium), Michael F. Gable (Willimantic, CT, USA), Wanda Plaiti (Heraklion, Greece) publishes the proceedings of the Xth International Colloquium on Amphipod4 Heraklion,Crete,Greece, lG2l April 2000.