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We determined seasonal cycles of lipid content, lipid class composition, and carbon and nitrogen content of seven taxa of zooplankton that were collected from the Beaufort Sea shelf, Canadian Arctic, over a 10-month period (September 2003-August 2004). All taxa except the chaetognath Parasagitta elegans had substantial lipids stores (>50%), either seasonally (Oikopleura spp.) or throughout the year (Calanus hyperboreus, Calanus glacialis, Paraeuchaeta glacialis, Metridia longa, and Eukrohnia hamata). Wax esters were the dominant lipid class in the chaetognath Eukrohnia hamata and in all copepods, including the carnivore Paraeuchaeta glacialis. Seasonal trends in lipid content and composition varied among taxa; some taxa had little variation from winter through summer (e.g., Parasagitta elegans), other taxa showed little variation until summer (e.g., Calanus glacialis), and others showed increasing or decreasing trends during winter and spring (e.g., Calanus hyperboreus). Specifically, total lipid content of Calanus hyperboreus decreased from January through May at a rate of ~450 µg x [month.sup.-1] x [individual.sup.-1] in adult females and ~100 µg x [month.sup.-1] x [individual.sup.-1] in juvenile copepodite IV, representing a 75%-85% loss in lipid. Nous avons determine les cycles saisonniers du contenu en lipides, de la composition des classes de lipides et des contenus en carbone et en azote de sept taxons de zooplancton preleves de la plateforme de la mer de Beaufort, dans l'Arctique canadien, sur une periode de 10 mois (de septembre 2003 a aout 2004). Tous les taxons a l'exception du chetognathe Parasagitta elegans presentaient d'importants stocks de lipides (>50 %), soit sur une base saisonniere (Oikopleura spp.) ou durant toute l'annee (Calanus hyperboreus, Calanus glacialis, Paraeuchaeta glacialis, Metridia longa et Eukrohnia hamata). Les esters cireux constituaient la classe de lipides dominante chez le chetognathe Eukrohnia hamata et chez tous les copepodes, dont le carnivore Paraeuchaeta glacialis. Les tendances saisonnieres du contenu et de la composition lipidiques variaient selon le taxon; certains taxons presentaient peu de variations de l'hiver a l'ete (p. ex. Parasagitta elegans), d'autres presentaient peu de variations jusqu';! l'ete (p. ex. Calanus glacialis), alors que d'autres encore presentaient des augmentations ou diminutions durant l'hiver et le printemps (p. ex. Calanus hyperboreus). Plus precisement, le contenu en lipides total de Calanus hyperboreus diminuait de janvier a mai a un taux de ~450 µg x [mois.sup.-1] x [individual.sup.-1] chez les femelles adultes, et de ~100 µg x [mois.sup.-1] x [individual.sup.-1] chez les copepodites juveniles IV, ce qui constitue une diminution des lipides de 75 % a 85 %. [Traduit par la Redaction], Introduction Primary production in the Arctic Ocean is highly seasonal and episodic. Some zooplankton populations respond quickly to these ephemeral phytoplankton blooms with high rates of feeding. The energy obtained [...]