A year/long ice camp centered around a Canadian icebreaker frozen in the arctic ice pack successfully collected a wealth of atmospheric, oceanographic, and cryospheric data.

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This paper synthesizes the trophic dynamics of a Canadian arctic marine ecosystem in so far as it is known, using new data on primary production, zooFlankton, the bivalve Mya truncata, and arctic cod (Boreogadus saida), as well as literature values for marine mammals and seabirds. The 98 000 km reglon has a high rate of primary production relative to other parts of arctic Canada. About 60 g Cm-' are fixed annually, of which approximately 90% is contributed by phytoplankton, 10% by ice algae, and 1% by kelp. Phytoplankton production is twofold higher along the south coast of Comwallis Island than elsewhere in Barrow Strait. Four copepod species, of which Pseudocalanus acuspes is the most important energetically, graze about one-third of the phytoplankton production. Bivalves maintain high biomass but low energy flow, acting as sedimenting agents. Arctic cod is a major component, with 125 000 tonnes bein consumed by marine mammals and 23 000 tonnes by seabirds annually. Our hydroacoustic estimate for mean arctic cod density, 0.0022 fish.m', is probably too low, partly because we have been unable to quantify dense aggregations of schooling fish. The ecological efficiency of ringed seal is near maximum, with 5% of ringed seal ingestion going to bears and man as seal flesh. The data on total kill and prey consumption in whales and birds is incomplete because they migrate out of the Lancaster Sound region in winter. The food chain is very long, with bears occupying the fifth trophic level; this is reflected by high biomagnification factors for persistent lipophilic pollutants such as PCBs. There are major data gaps for some zooplankton and most of the benthos, as well as for winter populations and energetics. This trophic analysis is therefore incomplete and efficiencies for entire trophic levels cannot be calculated.RgSUMfi. Cet article rBsume la dynamique trophique de 1'6cosysttme marin dans le Canada arctique dans la mesure oh il est connu, en utilisant de nouvelles donntes sur la production primaire, le zooplancton, le bivalve Mya fruncata, et la m o m polaire (Boreogadus saida), ainsi que les valeurs trouvees dans la documentation sur les mammieres et les oiseaux marins. Cette rigion d'une superficie de 98 000 k m ' posstde un taux BlevC de production primaire par rapport B d'autres parties du Canada arctique. Environ 60 g C.m-' sont fix& annuellement, dont environ 90 p. cent par le phytoplancton, 10 p. cent par les algues glaciaires et l p. cent par les laminaires. La production de phytoplancton est deux fois plus Blevte le long de la c6te meridionale de l'ile Comwallis qu'ailleurs dans le dCtroit de Barrow. Quatre esp&ces de cop6podes, dont la Pseudoculunus acuspes est la plus importante du point de vue tnergitique, utilisent environ un tiers de la production de phytoplancton pour se noumr. Les bivalves contribuent de faGon importante A la biomasse mais peu au flux BnergBtique, Ctant des agents de s6dimentation. La morue arctique est une composante importante, itant consommBe au taux annuel de 125 000 tonnes par...