| Summary: | The proportion of caloric energy associated with each of the macrozooplankton populations at two stations in upper Frobisher Bay was determined at intervals during three consecutive open-water seasons. In the upper 50 m of the water column three species (the ctenophore Mertensia ovum, the chaetognath Sagitta elegans, and the hyperiid amphipod Parathemisto libellula) consistently accounted for 90% of the caloric content of the marcozooplankton community. The ctenophore dominated the samples and accounted for 60-95% of the total calories. In deeper water (>70 m) euphausiids, primarily Thysanoessa inermis, accounted for most of the macrozooplankton calories. Ctenophores do not appear to be major prey of arctic marine vertebrates. Thus, in Frobisher Bay surface waters a large proportion of the available energy ends up in an apparent trophic dead end of low specific caloricity. The ctenophores' precise role in this northern marine ecosystem is as yet unclear.Key words: macrozooplankton, Frobisher Bay, caloric content, Mertensia ovum, ctenophores, Sagitta elegans, Parathemisto libellula, Thysanoessa inermis Mots clés: macrozooplancton, baie Frobisher, contenu calorique, Mertensia ovum, cténophores, Sagitta elegans, Parathemisto libellula, Thysanoessa inermis
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