Energy Flow through the Marine Ecosystem of the Lancaster Sound Region, Arctic Canada

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, zooplankton, the bivalve Mya truncata, and arctic cod (Boreogadus saida), as well as literature values for marine mammals and seabirds. The 98 000 km² region has a high rate of primary production relative to other parts of arctic Canada. About 60 g C.m⁻² 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 Cornwallis 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 being consumed by marine mammals and 23 000 tonnes by seabirds annually. Our hydroacoustic estimate for mean arctic cod density, 0.0022 fish.m⁻², 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. /// Cet article résume la dynamique trophique de l'écosystème marin dans le Canada arctique dans la mesure où il est connu, en utilisant de nouvelles données sur la production primaire, le zooplancton, le bivalve Mya truncata, et la morue polaire (Boreogadus saida), ainsi que les valeurs trouvées dans la documentation sur les mammifères et les oiseaux marins. Cette région d'une superficie de 98 000 km² possède un taux élevé de production primaire par rapport à d'autres parties du Canada arctique. Environ 60 g C·m⁻² sont fixés annuellement, dont environ 90 p. cent par le phytoplancton, 10 p. cent par les algues glaciaires et 1 p. cent par les l