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

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.