Feeding of <Emphasis Type="Italic">Themisto libellula</Emphasis> (Amphipoda Crustacea) on natural copepods assemblages in an Arctic fjord (Kongsfjorden,Svalbard) |
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Authors: | Margaux Noyon Stéphane Gasparini Patrick Mayzaud |
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Institution: | 1.Laboratoire d’Océanographie de Villefranche,UPMC Univ Paris 06, UMR 7093,Villefranche-sur-mer,France;2.Laboratoire d’Océanographie de Villefranche,CNRS, UMR 7093,Villefranche-sur-mer,France |
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Abstract: | Ingestion rates and selectivity of the Arctic pelagic amphipod Themisto libellula were studied experimentally in Kongsfjorden (Svalbard, 78°N) during the summer period. Feeding incubations were conducted
on naturally occurring copepod communities at different concentrations ranging from 25 to 250 preys L−1. The ingestion rates increased with food availability from 1.3 to 17.7 preys ind−1 day−1, which corresponded to 0.3–11% of body carbon day−1. Despite the high prey concentration used in the experiments the satiation level was not reached. We suggested that T. libellula is able to take the maximum benefit from dense patches of preys, which represent a good adaptation to the high variability
in food supply characteristic of polar environment. Copepodids stage III of Calanus spp. appeared to be the preferred preys of T. libellula. Smaller copepods such as Oithona similis and Pseudocalanus spp., were also selected but only when their relative abundance exceeded 25% of the total prey available. The potential predation
impact of T. libellula is discussed in relation to the mesozooplankton small-scale patchiness and predator abundance. |
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