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Effects of sea-ice extent and krill or salp dominance on the Antarctic food web

Nature volume 387, pages 897–900 (1997)Cite this article

Abstract

Krill (Euphausia superba) provide a direct link between primary producers and higher trophic levels in the Antarctic marine food web1,2,3,4,5,6. The pelagic tunicate Salpa thompsoni can also be important during spring and summer through the formation of extensive and dense blooms6,7,8,9. Although salps are not a major dietary item for Antarctic vertebrate predators7,10, their blooms can affect adult krill reproduction and survival of krill larvae. Here we provide data from 1995 and 1996 that support hypothesized relationships between krill, salps and region-wide sea-ice conditions11,12. We have assessed salp consumption as a proportion of net primary production, and found correlations between herbivore densities and integrated chlorophyll-a that indicate that there is a degree of competition between krill and salps. Our analysis of the relationship between annual sea-ice cover and a longer time series of air temperature measurements12,13 indicates a decreased frequency of winters with extensive sea-ice development over the last five decades. Our data suggest that decreased krill availability may affect the levels of their vertebrate predators. Regional warming and reduced krill abundance therefore affect the marine food web and krill resource management.

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Figure 1: Location of the Elephant Island survey area near the Antarctic Peninsula.
Figure 2: Long-term trends in mean annual surface air temperature in the Antarctic Peninsula region 1947–1995 (circles) and the regional sea-ice index 1979–1995 (squares).

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Acknowledgements

We thank S. Bros, G. Cailliet, D. Outram, R. Phleger, E. Shulenberger, M. White and K. Wishner for comments, and S. Nocol for helping to improve the manuscript. This work was supported by the National Oceanic and Atmospheric Administration U.S. Antarctic Marine Living Resources Program. Additional support came for the National Science Foundation (W.F., W.T. and S.T.) and the Institut für Seefischerei (V.S.).

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Authors and Affiliations

  1. *Moss Landing Marine Laboratories, P.O. Box 450, Moss Landing, 95039-450, California, USA

    V. Loeb

  2. †Institut für Seefischerei, Bundesforschungsanstalt für Fischerei, Palmaille 9, 22767, Hamburg, Germany

    V. Siegel

  3. ‡Scripps Institution of Oceanography, University of California at San Diego, La Jolla, California, 92093-0202, USA

    O. Holm-Hansen

  4. §National Marine Fisheries Service, Southwest Fisheries Science Center, P.O. Box 271, La Jolla, 92038, California, USA

    R. Hewitt

  5. ‖Department of Biology, Polar Oceans Research Group, Montana State University, Bozeman, 59717, Montana, USA

    W. Fraser, W. Trivelpiece & S. Trivelpiece

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  1. V. Loeb
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  7. S. Trivelpiece
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Correspondence to V. Loeb.

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Loeb, V., Siegel, V., Holm-Hansen, O. et al. Effects of sea-ice extent and krill or salp dominance on the Antarctic food web. Nature 387, 897–900 (1997). https://doi.org/10.1038/43174

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