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Effects of the Hudson Strait outflow on the biology of the Labrador Shelf

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Abstract:

Physical, chemical, and biological data collected on the Labrador Shelf in September 1985 are used to examine a hypothesis that the nutrient influx from Hudson Strait increases primary production on the northern shelf and this supports a "conveyor belt" food chain as the community is transported southward by the mean circulation. This hypothesized influx of production was proposed to account for the higher fish abundance on the southern Labrador Shelf. If true, the hypothesis suggests that the relative importance of higher trophic levels generally should increase southeastward along the shelf. Our results confirm that high nutrient levels occur on the northern Labrador Shelf in summer because of continuous advection of nutrients from Hudson Strait and this enhances local plankton production. However, nutrient, chlorophyll a, plankton species, and biomass spectra distributions generally do not support the idea that a developing food chain is advected progressively southward along the shelf. The large fish population on the southern Labrador Shelf appears to have been more dependent on production supported by local upwelling around Hamilton Bank than on food advected from the north.

Des données physiques, chimiques et biologiques relevées sur la plate-forme du Labrador en septembre 1985 ont permis d'évaluer l'hypothèse selon laquelle l'influx de nutriments par le détroit de Hudson augmente la production primaire sur la plate-forme nord et qu'il entretient une chaîne alimentaire de type « courroie de transmission » à mesure que la communauté dérive vers le sud, emportée par la circulation moyenne. Cet apport de production a été suggéré pour expliquer l'abondance plus grande de poissons sur la partie sud de la plate-forme du Labrador. Si l'hypothèse est exacte, l'importance relative des niveaux trophiques supérieurs sur la plate-forme devrait augmenter vers le sud. Nos résultats confirment l'existence de fortes concentrations de nutriments sur la partie nord de la plate-forme du Labrador en été à cause de l'advection continuelle de matières nutritives depuis le détroit de Hudson, ce qui favorise la production locale de plancton. Cependant, les données sur les nutriments, la chlorophylle-a, la composition spécifique du plancton et les spectres de distribution de la biomasse n'appuient pas l'hypothèse qu'une chaîne alimentaire se développe progressivement par advection vers le sud de la plate-forme. Le fort peuplement de poissons sur la partie sud de la plate-forme du Labrador semble donc dépendre plus de la résurgence locale autour du banc de Hamilton que d'un apport de nourriture arrivant du nord.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: January 1, 2001

More about this publication?
  • Published continuously since 1901 (under various titles), this monthly journal is the primary publishing vehicle for the multidisciplinary field of aquatic sciences. It publishes perspectives (syntheses, critiques, and re-evaluations), discussions (comments and replies), articles, and rapid communications, relating to current research on cells, organisms, populations, ecosystems, or processes that affect aquatic systems. The journal seeks to amplify, modify, question, or redirect accumulated knowledge in the field of fisheries and aquatic science. Occasional supplements are dedicated to single topics or to proceedings of international symposia.
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